4th
Generation (1993 - Present)
4.2 Engine/Induction/Exhaust
4.2.1 General
4.2.2 Induction
4.2.3 Internal
4.2.4 Exhaust
4.2.5 Ignition
4.2.6 Fuel
4.2.7 Cooling
Q: What's the difference between the LT1 and its predecessor the L98?
A: There is a recent SAE paper that compares and contrasts the two engines. It discusses history, cooling, lubrication, breathing, ignition, etc. The name of the paper is "New Generation Small Block V8 Engine," SAE paper 920673, by Anil Kulkarni of GM. It can be obtained from the SAE by calling 412-776-4841.
Q: What's the difference between the F-body LT1 and that in the Corvette?
A: The engines are exactly the same with the exception of the air intake and the exhaust. Also the Corvettes have two knock sensors and 4-bolt mains compared to 1 knock sensor and 2-bolt mains on the F-Bodies, respectively. The Corvette has a larger/wider air intake box plus a dual muffler/exhaust that accounts for the additional 25hp. The F-Body is also supposed to have a redesigned oil pan as the Corvette one doesn't fit with the F-body cross-member.
Q: What's the difference between the F-body LS1 and that in the Corvette?
A: the engines were basically the same. The camshaft in the F-Body's are milder, and the intake manifold and exhaust were both more restrictive than the Corvette's.
Q: How much horsepower does the LS1 really have?
A: This is an interesting question that has sparked many debates recently. From 1997 up until 2000, the LS1 in the Corvette had an advertised 345 HP. From 1998 up until 2000 the LS1 in the Camaro Z28 and Pontiac Trans Am had an advertised 305 HP, and the horsepower in the Camaro SS and Trans Am WS6 had an advertised 320 HP.
It is pretty much believed that the HP ratings on the F-bodies are underrated. GM didn't want the F-bodies to be too close to their flagship Corvette, however the HP output between the two cars is actually very close. The Corvette is a little higher, and 345 HP is a realistic measurement, however the F-bodies are actually closer to 325-340HP. Depending on whether you have an automatic or a 6-speed, your HP rating will vary due to the automatics having more drivetrain loss. Most LS1 F-bodies are dynoing between 270 and 290 rear wheel horsepower depending on the transmission.
The best way to find out how much HP your LS1 puts out, is to take it to a dyno because each car is a little different. There is a slight increase in HP with the SS and WS6 cars because they have freer flowing intake air and a better exhaust, but the difference is maybe only 10-20 HP. If you have a regular Z28 or Trans Am, then realize that your 305 HP car is really underrated by at least 20 or more horsepower.
The Corvettes will still post slightly better 1/4 mile times, even though they have pretty close to the same HP output only because they have a better 50/50 weight ratio, they have 18 inch wheels in back (more grip), and are a little more aerodynamic. However the Corvette will only really start to pull on an F-body at speeds of 100 or greater.
With a little bit of modifications, if is VERY easy to get the LS1 F-body into the 350 HP+ range.
Q: How long is the break in period on my LS1?
A: Although this varies between car to car, and each person you ask can have a different answer, here are some pretty general things to observe when you car is brand new.
Before 500 miles:
When you car hits 500 miles, you should probably change your oil. Most people stick with regular "dino" oil for the first oil change. The Corvettes come from the factory with synthetic oil, so putting in synthetic this early shouldn't harm anything, but you want to change your oil very early to get the metal shavings out of your oil. If you're going to be doing this relatively quickly, putting in synthetic is a waste of money since it costs significantly more.
Once you hit the 500 mile marker, it's pretty safe to say your car is as broken in as its going to get. The LS1 engine normally takes anywhere from 2000-6000 miles to fully break in, and thus give its best performance. People who test their engines with only a couple hundred of a thousand miles on it are often disappointed at their car's performance. If you vary your driving habits within the first few thousand miles, your car's engine will liven up relatively quickly.
Q: My LS1 car idles rougher than my LT1 car, is this normal?
A: Yes, the LS1 has a different cam, which makes the car have a bit of lope at idle. People have reported that replacing the factory spark plugs with better ones like NGK TR55s and wires smoothened out the idle a bit.
Q: Does the LS1 use reverse-flow cooling like the LT1 did?
A: No. GM Went back to the standard cooling configuration for the LS1. The LT1 cools the heads first while the LS1 cools the heads last. Each system has their advantages and disadvantages. With reverse cooling there is the risk of hot-spots on the cylinder walls. Because of this care should be taken whenever any type of cooling system maintenance is done on an LT1 engine.
Q: How do I make a different size engine?
A: I'm just gonna show the common overbores, but with custom pistons, you can make what you want.... There are probably some rounding errors present as well, but are close enough for comparison purposes.... (Terry Hartman thartman@flash.net)
|
|
Bore Size |
||||||
|
Block |
Stroke |
4.000 |
4.030 |
4.060 |
4.125 |
4.155 |
4.185 |
|
Chevy 350 |
3.48" |
349.800 |
355.070 |
360.377 |
|
|
|
|
Chevy 350 |
3.75" |
376.944 |
382.619 |
388.377 |
|
|
|
|
Chevy 350 |
3.85" |
386.995 |
392.823 |
398.693 |
|
|
|
|
Chevy 350 |
3.875" |
389.557 |
395.423 |
401.332 |
|
|
|
|
Chevy 350 |
4.0" |
402.073 |
408.127 |
414.226 |
|
|
|
|
Chevy 350 |
4.125" |
424.743 |
431.138 |
437.581 |
|
|
|
|
Chevy 400 |
3.75" |
|
|
|
400.871 |
406.723 |
412.617 |
|
Chevy 400 |
3.85" |
|
|
|
411.561 |
417.569 |
423.621 |
|
Chevy 400 |
3.875" |
|
|
|
414.285 |
420.333 |
426.425 |
|
Chevy 400 |
4.0" |
|
|
|
427.595 |
433.838 |
440.125 |
|
Chevy 400 |
4.125" |
|
|
|
441.013 |
447.451 |
453.936 |
Q: Is there anything I should be concerned about when flushing my radiator on a LT1 F-Body?
A: Yes, there are several things. First, you should take great care in keeping any coolant off of your Optispark, which is located in the front bottom portion of the engine. This is especially important on 93 and 94 models, as they are not properly vented. Water will destroy your Optispark. When filling your cooling system back up, make sure that you bleed the cooling system by opening to 2 valves on top of your engine. This will allow for air-bubbles to escape. Once again though, be careful, as the valves are located directly above the Optispark.
A: Although this hasn't been proved by a TSB, most people with 1999 LS1 F-bodies appear to have a problem with the temperature meter that makes it constantly read 210. If you run an Autotap on that car, you will see the temperature correctly displayed, so the problem must only be with the gauge, and not the computer. The 1998s don't appear to have this problem.
Q: Can I overbore the LS1 like I could all previous Chevy small blocks?
A: Yes and no. The LS1, unlike the LT1 uses thin Iron liners that are cast into the block at the foundry. Because of this, over-bore is limited to .005" overbore. Rumor has it that the 99' LS1 will bring a thicker sleeve which will allow for a .015" - .020" possible overbore.
Q: What is the firing sequence for the LT1/LS1?
A: LS1: 1-8-7-2-6-5-4-3 LT1: 1-8-4-3-6-5-7-2 The cylinders are numbered the same as in previous years.
Q: What is OBD? What is the difference between OBD-1 and OBD-2?
A: Information taken from Alex C. Peper at http://www.obd-2.com.
OBD is an abbreviation for On Board Diagnostics.
OBD-1 is in reference to Title 13 California Code 1968 titled "Malfunction and Diagnostic System for 1988 and Subsequent Model Year Passenger Cars, Light-Duty Trucks, and Medium-Duty Vehicles with three-way Catalyst Systems and Feedback Control." filed on 11-15-85. This required cars sold in California to have an on-board computer processor for on-board self diagnostics of computer sensed emission related components, fuel metering device and EGR (exhaust gas recirculation system). A partial or total malfunction that exceeded exhaust emission standard would illuminate a MIL (malfunction indicator light) and provide on-board identification of the malfunction location. To provide malfunction location information, codes are stored in on-board computer memory. To read codes manufactures use methods, such as flashing MIL light or various serial data protocols.
OBD-2 is in reference to Title 13 California Code 1968.1 titled "Malfunction and Diagnostic System Requirements-1994 and Subsequent Model-Year Passenger Cars, Light-Duty Trucks, and Medium-Duty Vehicles and Engines. Filed on 8-27-90 to Air Resource Board (ARB), this requires a standard electrical connector, open source standardized diagnostic trouble codes (DTC), data, and communication protocol with more specific self-diagnostic on-board monitoring of emission malfunctions.
The 12 step system monitoring requirements are:
Q: Why don't F-Body LT1s and LS1s get synthetic oil at the factory like Corvettes do?
A: Some Corvette LT1s do not have an engine oil cooler as the f-body cars do. Since this may cause the Corvette LT1 to run somewhat hotter, synthetic oil is used for its ability to withstand higher temperatures without thermal/ viscosity breakdown, although, Corvettes with the performance suspension are supposed to have oil coolers.
Q: Should I use synthetic oils?
A: This question is as old as which gas should I use, and which is better, Ford or Chevy. Some people will tell you it makes a difference, others will tell you it's a waste of money. Here are the facts that you can use to make your own decision.
There really is no answer to this question, so I would just ask someone else who has an LS1 and see what they say.
Q: What brand of synthetic/dino oil should I use?
A: Once again, no real best answer here. As for synthetic, GM endorses Mobil 1, so it doesn't hurt to go with that GM uses, however just about any synthetic or dino oil will be fine, as long as its approved to be used in your car.
Q: What weight oil should I use in my LS1?
A: 5W30 is probably your best bet. If you live anywhere other than places where it constantly gets above 95 degrees F then you'll want to use 5W30. For people who live in hot climates, go ahead and try 10W30, however I would not use 10W40 or higher.
Q: My manual for my 1998 F-body says to use a PF24 oil filter but that's way too big to fit.
A: This was an error in the 1998 manuals. An addendum was sent to the original owners of these cars, but over time, this may have been lost. The correct AC Delco oil filter is the PF44. If you would like to use a larger filter that holds more oil, go with the PF58, it has the same threads and same diameter, just it's a longer filter. If you are interested in using filters made by other manufacturers, here's a list of other brands and their filters. Ones with (L) next to them are the larger equivalents. This information was also taken from the LS1.COM FAQ at www.ls1.com.
|
Mobil 1 M1-107 |
Mobil 1 M1-206 (L) |
|
Fram PH 3506 |
Fram PH 3675 (L) |
|
Purolator L14006 |
Purolator L20123 (L) |
|
Motorcraft FL-331 (L) |
Hard Driver HD08 (L) |
|
PureOne PL20123 (L) |
NAPA 1045 (L) |
|
WIX 51045 (L) |
Amsoil ASF 30 (L) |
|
Deutsch 377 |
|
Q: What is a Y-Pipe, and will replacing it help in performance any?
A: The Y-pipe connects to each exhaust manifold and then connects to the catalytic converter. The stock Y-pipe is fairly restrictive. On the 98+'s the SLP y-pipe sits approximately 2" lower. On a stock height F-Body this should not cause any problems. Lowered F-Body's might encounter some minor clearance problems.
Q: What are the K&N filter Part Number for the 1998 Z28?
A: According the list members, the proper part number is #33-2111. Be warned the part number #33-2014 fits, but not properly.
Q: Which cars got an engine oil cooler?
A: Oil coolers were only available on the 1993 - 1995 models. And even then, the oil cooler did not come standard on F-bodies. You got the oil cooler as part of one of the preferred equipment options on a 6 speed car, or if you ordered an automatic equipped car with the performance rear axle. It also came on any car equipped with the 1LE option package.
You could not get the oil cooler on an automatic equipped car which came with 2.73 rear end gearing. You could not get the oil cooler if you order a 6 speed car and then did not order either the 1LE option package or one of the preferred equipment groups.
You can visually inspect your car for the oil cooler. It's simply a metal tube running from above the oil filter to the radiator (carrying antifreeze for cooling) and then back to engine block. The sticker in the glove box should also have a "KC4" which is the option code for the oil cooler.
Some owners of 1995 Formulas and Trans Ams (which should have the cooler based on having an option above), actually claim they don't. It's not yet known why, since sales literature says they should.
Q: Why has oil coated the underside of my engine and transmission?
A: It's most likely that the seal around your intake manifold is leaking. While it was originally thought to be the intake manifold gasket itself leaking, it's now found to be the sealant being used. The reason is a gasket is only applied to the left and right sides of the manifold while the front and back is sealed with RTV sealant. If the sealant is applied to a surface, which isn't clean, the oil will be able seep through. This is why the oil leak is usually found at the rear of the engine (dripping down onto the transmission). It can be easily mistaken for a rear main seal leak. And since the RTV sealant is used on the front of the intake manifold, it's not uncommon to find it leaking there, too. A classic symptom of this intake leak is a rough cold idle. There is a Technical Service Bulletin (#476111) which calls for the replacement of intake gasket with a new and improved one. This is to deal with the problem of the actual gasket (used on the left and right sides of the intake) laminate burning and causing a foul odor to enter the car through the ventilation system. If you have a 1994 F-Body, you might be able to get your oil leak fixed using this TSB (even though it's for a separate, but closely related problem). Otherwise, you'll have to have the dealer verify the leak, which will likely be running black-light dye through the engine. The revised gasket kit is part # 12524653.
Another theory on why this intake oil leak problem exists is that it is due to the EGR location. When the EGR valve opens, allowing hot exhaust gasses to flow through the intake manifold, it heats a localized spot on the manifold. This uneven heating causes the rear corner of the manifold to warp and lift, very slightly, causing the RTV to break its seal and start to leak. The only way to fix this will be to remove the EGR system. Removing the EGR system will violate federal emissions laws.
Other, less common areas to check for leaks include the oil pan gasket, the oil dipstick tube seal (where it enters into the oil pan), and the timing chain cover seal.
Q: Why has my oil pressure reading suddenly started to drop at higher RPMs?
A: Several things can cause a low pressure reading at higher RPMs:
Q: What's that foul, burnt smell coming in the vents at stoplights?
A: First, be sure you don't have the oil leak problem mentioned above. If not, You may have a problem with oil leaking from the O-ring seal around the tailshaft. It drips onto the Y-pipe and burns off with the odor being sucked into the ventilation system. Reports of replacing the seal (part # 8673526) and bushing (part # 6260048) seem to fix the problem. Check with your dealer as these parts are supposed to have been improved/upgraded.
Q: What air intake (induction) upgrades are available? (All)
A: A number of companies sell replacement air intakes for between $130 and $350. Using of one of these intakes along with a K&N air filter can be good for a 10-20 hp increase. An aftermarket exhaust should be installed in addition to an aftermarket induction system for the best performance gains. Although, nothing says one mod should be done before the other. Here are some companies providing systems:
Arizona Speed&Marine 602-437-2510
C&L Performance 205-882-6813
Callaway 800-231-1121
Car Pro Motorsports 800-670-8862
GM Performance Parts (local dealer)
Hennessey 703-849-5081
L.G. Motorsports 214-272-7753
Lingenfelter 219-724-2552
K&N Filtercharger (local shop)
Paxton/Granatelli 805-987-5555
Random Technologies 770-978-0264
Saga Enterprises 909-275-0726
Prices range from $150 to $300 depending on the extent and the quality of replacement parts. Kits like Hennessey are plastic and replace the air box right up to the MAF, while Arizona S&M are chrome replacing the air box up to the MAF as well. Saga has a bolt-on scoop, which goes under the front driver-side fender, giving a ram-air effect into the stock set-up.
One other alternative is the Tornado Air Management System (800-500-8880) which costs around $70. It's a centrifugal air accelerator that fits into the air intake between the air filter and throttle body. It swirls the air, thereby accelerating it (like ram-air) and smoothes the flow reducing turbulence and allowing more air to be available per cubic inch for combustion. While this theory applies to a carberated vehicle, it does nothing for a fuel injected vehicle.
Q: What is the "Free Ram-Air Mod" for the 98+ LS1 F-Body's?
A: This is indeed a free mod, and is worth about 10-15hp. To take advantage of the full benefit of this mod, it should be done with a K&N filter. Thanks to Rob Glover for the documentation and Karl Witt for the idea.
For diagrams on this mod go to HTTP:\\OMAHA.F-BODY.ORG\ROB\98Z\RAMAIR
Q: How can I make my own air intake without spending a lot of money?
A: This mod currently applies only to the '93 - '97's. See "Free Ram AIR" elsewhere in this FAQ for the 98's. While it may not look like the aftermarket chrome and molded plastic ones available, this is a sure-fire, bang-for-the-buck way to create your own air intake for a significantly smaller amount of cash.
Most of the following items can be bought at your local parts store or speed shop for around $50. The K&N filter is going to be 80% of that cost. You will need to buy a K&N filter (RE-0870, 9 inch conical air filter, or one of similar size and shape), a 2 to 3 foot long and 4 to 4.5 inch wide flexible hose (Mighty Flow brand intake ducting, part# 96074, works very well), two 4 inch clamps, a 1 inch clamp, and a small Fram (or other brand) crankcase filter. If the K&N filter includes its own clamp, then you only need to buy one 4 inch clamp. If you can't find any type of intake ducting hose, you can use flexible hosing like that on your clothes dryer, but this type of hose isn't too rigid and can be easily crushed by the hood. Plus it's difficult to clamp since it's relatively soft.
Installation on the 1993 cars is going to be a little tricky. Since the 93's are speed density, they don't have a Mass Air Flow (MAF) sensor (like the 94+) which connects your intake hose to the rubber snorkel/elbow going into the throttle body. You'll need to find an INFLEXIBLE piece of tube or hose with the same 4" - 4.5" diameter which you can clamp the intake hose and rubber snorkel/elbow to, thereby connecting the two. A piece of PVC pipe will work. Or you can saw off the end of the stock intake piece (which you are removing), and use that as your connection. The 94's and later make use of the existing MAF sensor, so there's no need to find an extra connecting piece.
On those cars with MAF sensors, use the rubber gasket that's on the stock intake piece (which you are removing) by putting it around the MAF. Then put your new flexible hose onto that. It increases the diameter of the MAF from about 3.5" to about 4" which helps the hose fit nice and snug.
Simply clamp the K&N filter onto the new flexible intake hose and drop it down through the hole that the stock intake piece was sitting in. Then connect the other end of intake hose to the MAF (or your makeshift pipe piece for the 93's). Everything should just lay snuggly in place. The last step is to clamp the small crankcase filter to the air pump hose (which was originally connected to the stock intake piece). Then you're set to go.
Q: What is and where can I get a 'Brad Brand' intake tube?
A: The 'Brad Brand' intake is a
welded tube to replace the dryer duct intake elbow on Vortech supercharged
93-97 f-bodies. People tipically gain 2# of boost by reducing the restriction
created by the dryer duct. You can find this item at Atlanta Chasis Dyno,
770-623-9789. The ATI supercharged cars also have a similar option using the Mufflex intake tube.
Yet another option would be to fabricate your own low restriction intake using
some common hardware store items like thin wall PVC and large diameter
non-collapsable rubber hose.
Q: What's that plastic tube which runs perpendicular to the air intake?
A: This is a noise reduction tube, which comes with cars with air conditioning. It stores air at heavy throttle as it cuts down on the sucking or howling sound some engines produce. It's not evident whether this interferes with airflow, but it's unlikely. From 1996 and on, all cars had the tube since AC became a standard feature that year. Cars with air conditioning "delete" (option C41), like the '93-'95 1LEs, do not get this tube. The piece without the tube can be ordered from a GM dealer. The '93 - '94 part number is 25147210 and '95 is 25157187. On the 98's this tube still exists in a different configuration. See the "Free RAM Air Mod" elsewhere in this FAQ for more details.
Q: What aftermarket performance items are available for the V6?
A: As with the LT1s, available modifications include K&N free flow filters, air induction kits from API (800-426-8967), Lingenfelter (219-724-2552), and RK Sport (800-214-8030). Dynomax and Borla exhaust systems are available from RK Sport. You can also get JBA headers, Nitrous Oxide systems, shorter rear gears, low temperature thermostats, computer reprogrammers, underdrive pulleys, and subframe connectors. Motorsports Technologies Inc. (MTI) (404-509-3494) carry most of these mods.
In addition, Crower Cams, among others, custom grind cams for V6s. You must supply the core camshaft to them to be reground to the new specifications. Typical specs are 10-15 degrees more duration and .010"-.015" more lift. Contact Crower Cams (619-422-1191) with a detailed note stating application, rpm range and desired specs if applicable.
Q: What aftermarket headers are available for the LT1?
A: The following shows the current aftermarket header manufacturers and details on their products:
Manufact. |
Size |
Flange |
Tubing |
Stainless |
Coating |
Dual-cat avail. |
Ariz S&M |
1 3/4 |
3/8 |
14ga |
No |
HPC (ceramic) |
Yes |
Edelbrock |
1 5/8 |
5/16 |
16ga |
Yes |
Black paint |
Yes |
Edelbrock |
1 5/8 |
5/16 |
17ga |
No |
Pro-Tech |
Yes |
Hooker |
1 3/4 |
|
|
No |
High temp black |
No |
Hooker |
1 5/8 |
|
|
No |
None |
No |
JBA |
1 5/8 |
3/8 |
14ga |
No |
None |
Yes |
MAC |
1 5/8 |
|
16ga |
No |
High temp coat |
No |
SLP |
1 3/4 |
|
|
Yes |
None |
Yes |
Note the Mac's high temperature coating covers the exterior and 2" of the interior. The Edelbrock's alternate between 1 1/2 and 1 5/8 on a cylinder by cylinder basis, alternating in the firing order. The JBA's are AR (Anti Reversion) style which start out 1 5/8, then into an AR tube, and come out at 1 3/4. The 1 3/4 Hookers are full-length headers with no O2 sensor bungs, no AIR tubes, with a collector exiting near mid-tail of transmission, and requires a custom y-pipe at tail of transmission to connect to stock exhaust system.
Q: What's the size of the LT1 throttle body and can I use a larger one?
A: A stock throttle body inlet is 48 mm in diameter. The matching inlet on the intake manifold which it's attached to is about 52 mm. Therefore, you can safely buy a 52 mm one (like that from TPIS) and bolt it on in place of the stock one without any other modifications. Anything larger (like the 58 mm job from Lingenfelter) would require the intake manifold to be bored out to handle in the increased volume of air. The larger throttle bodies are not physically larger, they've just been bored out making the openings larger.
The additional amount of HP from the 52mm throttle body is questionable. Some reports show little or no increase, yet others claim up to 10 more HP. And some airfoils (to smooth the flow through the throttle body) claim to get another 5 HP. But even that is questionable. A 58mm throttle body (in conjunction with the bored intake manifold) might provide a larger increase in HP, but once again, results usually vary.
Q: Why and how should I bypass the throttle body coolant lines?
A: A small amount of coolant is passing through the small hoses connecting to the throttle body. The main reason is so that during the winter months, the higher temperature of the coolant will keep the throttle body warmer thereby preventing icing. That's where the problem lies during the other months. By warming up the throttle body, you're warming up all of the air passing into the engine and thus losing some power (since cooler, denser air makes more power). It is also believed that during the hot, summer months the coolant pass-through works to cool off the throttle body. So you must be careful when bypassing this so as not to lose its benefits.
To do the bypass, first remove the small hose going into the throttle body on the driver side. You will probably have to remove the rubber intake elbow and black alternator brace. Make sure you have some rags handy to catch any coolant that my drip out. On the passenger side of the throttle body there are three hoses. Remove the lower one (which is very short and has a 90 degree turn to connect to a metal intake manifold hose). You may have to remove the other two hoses along with the sensors to get better access to the clamp. Then pull the disconnected driver side hose over, and connect it to the metal intake manifold hose from which you just disconnected on the passenger side 90 degree-turn hose. Hold onto that 90 degree hose in case you need it in the future.
Q: Why and how should I bypass the EGR valve/line?
A: The EGR re-routes some of the exhaust gases back into the intake/combustion chamber. This is basically done to reduce emissions. Blocking it off will reduce the temperature of the intake since the gases fed back through the EGR are very hot. Lower intake temperature produces more power, but the amount of gases that are passed through the EGR is VERY minimal and probably won't result in much (if any) performance gain. The drawback is increased emissions.
If you look at the back of the passenger side of the intake manifold, you will see a tube that runs up to the manifold from the exhaust manifold. Take the tube off, pull it back, and look at it. You will see a two bolt pattern with a hole in the middle. Make some kind of plate to block the hole and guided on the bolt hole. You can make the plate out of any piece of scrap metal (sheet metal is fine). Put the tube back on with the plate in place.
Q: Why and how should I relocate my idle air temperature (IAT) sensor?
A: The stock position of the IAT sensor (in the rubber intake elbow just before the throttle body) causes it to pick up a lot of intake manifold heat. This can be an extra 10 degrees F at highway speeds and 30 degrees F (or more) at idle. This causes the computer to retard the timing (zapping power) and causes the engine to run overly rich (since the MAF thinks there's more air going through it than there really is due to artificially high temperatures). By moving the IAT towards the air filter (away from the hot manifold), the ECM will get a more accurate reading of the actual intake temperature and will properly adjust the timing and fuel/air ratio. There's no need to worry about the air heating up more as it passes beyond the new location of the IAT since at wide open throttle, it takes the air 15/1000 of a second to travel from the air filter into the engine.
First, remove the IAT sensor from the bend in the rubber intake elbow. Then plug up the hole on the elbow with something. The site you relocate the IAT to will depend on what air intake (stock or after-market) you have. You want it as close to (if not, right in) the air filter. Snip the sensor wires first, as you can splice in lengths of wire after the sensor is in its new location. On a stock air box, you can drill a hole into the back of the box. On after-market intakes, try drilling a hole in the bottom of the air filter itself (works best on K+N conical filters) or on the pipe/tube to which the filter is connected. Either way, make sure the hole is placed in location which sees the air AFTER it passes through the air filter (otherwise debris may ruin the sensor). Then insert the sensor into the hole. After that, just splice wires to reconnect the sensor, solder the connections and protect with electrical tape or heat shrink-wrap.
Note, on ram air Pontiac cars (Firehawk and WS6), the IAT sensor is already located in the intake box. On ram air Chevy cars (SS), it doesn't appear you can relocate the sensor since the intake sits right over the hot intake manifold (which you're trying to get away from).
Q: What temperature is the stock thermostat and can I go lower?
A: Stock on the 4th generation cars is a 180 degree thermostat. This should be good enough for any but the most seriously modified car. Although, you can go down to 170 or even 160. Hypertech sells a 160 degree thermostat, which is supposed to be combined with their performance chips/programmers. And contrary to some opinions, the vehicle will not drop out of closed loop with 160 degree thermostat since that depends primarily on O2 sensor temperature, not engine temperature.
Q: What performance "chips/programs" are available?
A: For the 1993 cars, Hypertech, Jet Technologies, Z Industries and Superchips make replacement chips. HP increases vary from 15 up to 30. However, in 1994 and after, chips are soldered into the on-board computer and can't be removed. Hypertech gets around this with their Power Programmer, a hand- held "computer" which plugs into the PCM module under the driver-side dash, and reprograms the stock chip. Performance gains are almost the same as replacing the chip. The programmer costs about $300, considerably more than the $150 - $200 you'd expect to pay for a replacement chip.
The Hypertech Program increases redline and shift points (on auto transmission) by about 500 RPM over stock, and it improves the fuel and timing curves. The cooling fans are forced to coming on at lower temperatures. Any type of speed limiter will be overridden. It can also adjusting the speedometer for changes to aftermarket gears (like a 3.73). However, it doesn't modify the partial throttle shift points on cars with automatic transmissions. Thus, even with the programmer, partial throttle shifts will still occur at higher RPMs than with the stock gearing. But most companies can create a custom chip or program to overcome this.
The Programmer can also be sent back to Hypertech to be reprogrammed to take advantage of modifications like headers, camshafts, and superchargers. One other thing to remember is to run 92+ octane fuel with the chip/programmer. Otherwise the engine is probably going to knock due to the timing change.
Q: Can I keep the stock thermostat after installing a performance chip?
A: Yes, however you should do a little research first. Namely, find out if the new chip modifies the temperature at which the cooling fans come on and off. For instance, the Hypertech chip/program lowers the temperature at which the fans turn on and off. It turns the fans off at approximately 175 degrees F. This will a problem with the stock 180 thermostat because once the engine warms up enough to turn on the fans, the thermostat will cycle to bring the engine temperature down to 180 degrees F and keep it there. This could keep the temperature from getting down to 175 where Hypertech turns off the fans, and the fans could run continuously. This isn't bad for the engine, but it is bad for the fans in that it will probably burn out the fan motors.
Q: Can the fans be rigged to come on while the engine is not running?
A: The following instructions are for all mid-1994 to 1995 production models. Slide two wires into the underhood fuse/relay box in the D2 and J2 slots for the #1 fan relay (D) and #3 fan relay (J). Splice them together and run them through a 1 amp fuse. Hook another wire to the ground. Then, with the ignition on, connect the ground wire to the spliced fan wires and both fans come on at high speed. When you're not using the setup, remove the ground wire and tuck it away so you can't see it. The J2 slot is also connected to the F5 slot in the #3 fan relay, so you can use either one, it seems. This essentially provides the ground signal to the relays just like the PCM would when FAN CNTL A10 and FAN CNTL A11 codes are set in the PCM. The relays click when you make the connection, so everything should be working just like if the computer set both codes.
This set-up requires the ignition to be in the "On" position and requires no splicing/cutting of any stock wiring. This works great to cool off your car at the drag strip especially when the engine is off.
1993 and early-1994 cars don't have dual speed fans and therefore have no #3 (J) fan relay. For these cars you can just round a ground to D2 for the primary fan and F5 for the secondary one.
On 1996 and later models, the wiring has changed and the above procedure will blow the fan fuse and turn on the Service Engine Light. So instead, in the underhood fuse box, remove the relay labeled 'F'. Molded into the plastic on the box itself where the relay was is the letter 'F' as well as numbers for each connector. You want to connect the pin labeled '3' with the pin labeled '4'. Note that this is a real feed, and bypasses the relay, so use at least 14 gauge wire. Current is 12A startup, and 8A running. Use a switch that can handle the load.
Solder the wires to the bottom of the fusebox, and put the switch just in front of the box where there already is a unused hole. Black wires and a black switch makes it looks neat. With this setup, you can turn the fan on whenever you want, even with the engine off. Don't forget to put the relay back once you locate the correct connections. Without relay, a code is set and the Service Engine light is lit. If you happen to get a light, it won't go away until you reset the computer. The easiest way to do that is to disconnect the negative battery cable for about 1 minute.
Q: Why am I losing/smelling antifreeze, but nothing seems to be leaking?
A: Assuming you've checked the radiator cap and main hoses, it's possible your water pump is leaking. There's a small (2 mm) weep hole on the bottom of the pump. Black stains surrounding the hole indicate coolant seepage, which is an early warning sign of pump failure. Another indication of a pump leak is if there's green-black staining on the small rubber hose that plugs into the engine block (just behind the main crank belt pulley). Any coolant dripping out tends to drip directly onto the rubber hose where it then flows down to the hot engine block and is boiled off (leaving the staining). If you smell coolant at stop lights for instance, it's from it burning off on the block. Since the coolant boils off, the slow leak never has a chance to drip onto the ground, so you'll never see it.
Q: What fuel pressure setting will give me the best performance?
A: Stock settings on the 4th gens are around 43 to 45 psi. The best (adjusted) pressure seems to be variable depending on your cars specific modifications. But even cars with similar mods react differently to pressure adjustments. Some people claim 47 to 49 psi is best, while others find a lower setting like 39 to 42 psi is best. From testing, it seems the computer will adjust itself to a fuel mix level it is comfortable with. So even if you turn up the pressure to 53 psi, after a few wide open throttle runs, the computer will lean out with each successive run, bringing it down close to levels as though you were running 44 psi. So while adjusting the fuel pressure may have some effect, the computer retains a great deal (not 100%) of control as it will adjust the fuel mix based on each run. So you need to make multiple wide open throttle runs between adjustments of pressure to ensure you get to final equilibrium with the computer. The best way to find what's best for your car is trial and error.
Q: What brand or grade of gas should I use in my car?
A: This is an age-old question, perhaps asked as much as which is better, Ford or Chevy. There is no real answer to this question, but here is a post by ar15a2@aol.com on LS1.COM.
I'm in the fuel refinery business and maybe I can shed a little light. It's true that most of the fuel in a given area will come from the same bulk plant. I live in St. Louis, and all the Shell Mobil, and Amoco come from the Shell Terminal. Gasoline is a commodity and if you have a refinery in your area the gasoline comes from there, otherwise it gets to your area in one of the many pipelines that not many people know about. What makes Shell Shell and Mobil Mobil is the top secret additives that go in to the transport at the loading rack. As for Amoco Ultimate being clear, the sad news is that all refined gasoline is clear, They have to add the dye to identify the product. Also in every market there are two or three other bulk plants that supply the cut-rates and other stations that you would think would be OK.
Not so, the cut-rates are cheaper for a reason. Octane is made by adding something called aromatics , benzene, toulunal, Xylene etc. That stuff is the big expense. Typically gasoline that comes out of the pipeline will wholesale at .45 or .55 and after the taxes additives etc. it will retail for 1.099 for example. The taxes being the biggest part. When the /republicans whine about taxes and increases that Bill made, most of was in fuel tax.
Then if you live in an area that has the privilege of "reformulated fuel" the rules all change. Reformulated only means that they add an oxygenator to the mix (MBTE) or more often ethanol. It increases the amount of oxygen in the fuel but does squat for performance. The emissions are less. That is the name of the game. The point is that Amoco in Florida is not the same as in Chicago. Experiment, whatever works best, go with it. Stay away from the cut rates. I see what comes out of the filters and it isn't so nice. In my area Amoco Ultimate (5% benzene for now) works the best in my sled, but in other parts of the country another major oil will have what you want.
Q: What octane gas should I use in my car?
A: Well, once again, this is up to you, but first, lets explain what octane really is. Essentially, the higher the octane of gas, the more amount of oxygen it takes to burn the fuel. The more oxygen used to burn the gas means the quicker and cleaner it will burn. In larger, performance minded engines, you need to have a clean burning, fast fuel. Engines like the LS1 and LT1 have a computer, which is set to provide as much oxygen necessary to burn the fuel. Smaller displacement engines don't need a faster burning gas, and can get by with a lower octane gas, like 87. The computers in those cars are only set to give that engine so much oxygen per each spray of gas into the engine. If you put 93 octane gas in a car that's designed to run on 87, then the oxygen to gas ratio will be incorrect, and the fuel may not properly burn, thus harming the engine and performance of the car. So, getting to the point, if you run too low of an octane gas in an engine like the LS1, it is not putting more oxygen into the engine than necessary, so it will adjust the timing of the engine so it doesn't overdo it. Although this won't harm the engine, the fuel to air ratio will be less than optimal, and this will decrease your performance. So, running anything other than premium gas (which is usually between 92 and 94 octane depending on where you go) can potentially make your car run less than what it could. To be safe, the manufacturer recommends that you do not run anything lower than premium gas in the V8s.
Q: How easy is it to change the spark plugs on the LT1?
A: The easiest way is probably to remove the Y-pipe. Soak all the bolts with WD-40 (best done the night before) and remove them. The Y-pipe and cat should drop right out. Doing this, will give you access to all of the plugs from under the car, except for plug #2. For that one, it's easiest to remove the alternator to get at it from the top.
If you're into doing things the hard way (that is, not removing the Y-pipe), make sure you have a lot of time on your hands and a lot of band-aids for your hands and arms. Before you do anything, realize that the plugs are supposed to be good for up to 100,000 miles, but only time will tell.
Here's the best method (without Y-pipe removal) found so far:
PLUG |
ACCESS |
TOOLS REQUIRED |
COMMENTS |
1 |
Top |
Socket w/ Swivel |
Easy |
3 |
Top |
Socket w/ Swivel |
Easy |
5 |
Bot |
Socket w/ Swivel |
Slightly tricky |
7 |
Bot |
Socket w/ Swivel |
Watch out for O2 sensor |
2 |
Top |
Socket w/ Open End |
AC & Exhaust AIR Tubes make it NASTY |
4 |
Top |
Socket w/ Swivel |
Completely blind on this one |
6 |
Bot |
Socket w/ Swivel |
Difficult to reach, but doable |
8 |
Bot |
Socket w/ Swivel |
Skinny arms are a MUST |
NOTES:
A: The easiest way to do this on a 1998 F-body is to remove the rear 2 coils that are attached to the valve cover on the passenger side. These are held on by 2 10mm bolts and take about a minute to remove. On 1999+ cars, each side has all 4 coils connected to one bracket. Simply remove this bracket, and all 4 coils will come up at the same time.
Q: What spark plugs are available for the LT1?
A: Here's cross reference of the different plugs along with the part numbers:
|
Stock heat range: |
Colder range: |
|
AC Delco 41-906 (platinum, stock plug) |
AC Delco R42LTS |
|
AC Delco Rapidfire 3 |
Accel 514 |
|
AC Delco R44LTS |
Autolite 104 |
|
Accel 516 |
Bosch HR8DPX |
|
Autolite 106 |
Champion RS9YC |
|
Bosch HR9DPX |
Motorcraft AGRF42 |
|
Champion RS14YC |
Nippondenso T20EPR-U |
|
Motorcraft AGRF42 |
NGK BPR6EFS |
|
Nippondenso T16EPR-U |
|
|
NGK TR5 (.035 gap) |
|
|
NGK TR55 (.050 gap) |
|
|
NGK TR55VX (platinum version) |
|
Q: What are some common spark plug part numbers?
A: So far I only have 1.
|
Spark plug: |
Part number: |
|
NGK TR55 non-platinum |
3951 |
Q: Why has my car developed a bad hesitation problem (Optispark)?
A: First, check to your spark plugs wires and make sure none have come off. A few people have already experienced this problem. Then rule out any type of problem with the fuel system (injectors or pump) and air intake (loose clamp or hose). If those are okay, it's most likely your Optispark system. It's the pseudo-distributor of the distributorless LT1 where all the spark plug wires connect into. If water gets in there, it's as good as toast. Definitely head to your dealer to get it replaced as it will start eating your plug and wires in no time if there's something really wrong with it. A hesitation problem due to the Optispark will usually be noticed in certain RPM range. Most commonly, it is in the upper range (3500 - 5000 RPM). But it can certainly develop in the lower or mid ranges as well. You might even get some back-firing. The problem is most common on the 1993 and 1994 LT1s, as in 1995 a vacuum line was added from the intake manifold to the Optispark to draw moisture out of the unit. However, excessive water can cause even 1995 and later cars to develop the problem.
More information can be found here:
Mike Chaney's optispark disection page
Joe Gervais' vented
optispark page
Q: Why does my car have a slight stumble upon slow acceleration?
A: If it usually occurs from idle when then engine is warm and you get a short backfiring just before shifts, then it's probably the coil wire or the coil itself. If you notice the headlights flicker or flash at night when the car stumbles, it's almost assured the coil and/or coil wire need replacement.
Q: Should I use self-aligning or non-self-aligning rockers?
A: You can use either since the LT1 has screw in studs, but non-self-aligning rockers require guideplates. This means longer rocker studs are needed as well as hardened pushrods. And that means more money. But the advantage of the non-self-aligning ones is the reduced valve train noise.
Q: How do I adjust my aftermarket roller rockers?
A:
Method #1 (Rob Guy rsguy2@tecinfo.com)
Of course starting on one side at a time,
To check for coil bind:
When doing the roller rocker mod., this is a good time to modify the passenger side valve cover so the next time you want to take it off you don't have to remover the alternator. With the valve cover off, simply remover the first 3 supports (starting from the alternator side) from the inside of the valve cover. This is what I did to mine and it has never leaked. Just remember not to over tighten the valve cover bolts.
Method #2 (Michael Chaney mchaney@charm.net)
Installation is really simple, but save you some time by doing the following. The reason that people differ so much on the number of turns is because people differ in how much "clacking" they want to hear. If you don't mind noisy rockers, adjust them to 1/4 to 1/2 turn. If you want them noticeably quieter (but still louder than stock), crank them down to 3/4 to 1 turn.
As for the procedure, save you a "re-do" by not using the silly set screw to tighten them. Set the rocker to 1/4 turn less than what your goal is and then turn in the set screw until it stops (don't tighten it). Then turn the rocker nut itself another 1/4 turn or so which will tighten it down nicely. Most people I know of who just tightened the set screw ended up with one or more loosening up. For example, if you want 3/4 turn, set the rocker to 1/2 turn and take the slack out of the set screw. Then tighten the main nut down another 1/4 turn and you'll be at 3/4. Of course, if 1/4 turn is not enough to tighten the nut sufficiently, modify the above accordingly.
As for the procedure, here's what I did (for 3/4 turn).
A couple of notes: I don't install them and adjust them one at a time like everyone suggests. As long as you do the steps above (step (6) being one of the most important), installing them one at a time is absolutely useless and nothing but a waste of time. It is important though, that you at least set them all to zero lash prior to adjusting one. Also, remember or tag somehow the ones you have already done. They all start to look the same once you get into the job.
Q: What aftermarket camshafts are available for the LT1?
A: The following shows the current cams and their specs:
|
Manufacturer |
Part # |
Duration |
Lift (1.5) |
Lift (1.6) |
Lobe |
Notes |
|
|
|
Int Exh |
Int Exh |
Int Exh |
Sep |
|
|
CompCams |
08-304-8 |
210 220 |
500 510 |
533 544 |
114 |
|
|
CompCams |
CCA-215-224-14 |
215 224 |
499 499 |
532 532 |
114 |
2200-5700 |
|
CompCams |
CCA-218-224-14 |
218 224 |
503 504 |
527 538 |
114 |
|
|
CompCams |
CCA-220-230-14 |
220 230 |
510 510 |
544 544 |
114 |
(CC305)2500-6000 |
|
CompCams |
CCA-212-218-12 |
212 218 |
488 495 |
521 528 |
112 |
1200-5200 mild |
|
CompCams |
CCA-215-224-12 |
215 224 |
500 500 |
533 533 |
112 |
custom grind |
|
CompCams |
CCA-218-224-12 |
218 224 |
495 503 |
528 537 |
112 |
1600-5400 stk conv |
|
CompCams |
CCA-224-230-12 |
224 230 |
503 510 |
537 544 |
112 |
1900-5600 gears |
|
CompCams |
CCA-230-236-12 |
230 236 |
510 521 |
544 556 |
112 |
2200-5800 hvy mod |
|
CompCams |
CCA-230-242-12 |
230 242 |
510 510 |
544 544 |
112 |
|
|
CompCams |
08-306-8 |
230 244 |
510 540 |
544 576 |
112 |
(CC306)Heads,in,ex,hdrs |
|
CompCams |
CCA-236-242-12 |
236 242 |
521 540 |
556 576 |
112 |
2500-6000 all mod |
|
CompCams |
CCA-206-218-14 |
206 218 |
480 495 |
512 528 |
114 |
Nitrous/Blower |
|
CompCams |
CCA-212-224-14 |
212 224 |
487 503 |
519 537 |
114 |
Nitrous/Blower |
|
CompCams |
CCA-218-230-14 |
218 230 |
495 510 |
528 544 |
114 |
Nitrous/Blower |
|
CompCams |
CCA-224-236-14 |
224 236 |
503 521 |
537 556 |
114 |
Nitrous/Blower |
|
CompCams |
CCA-230-244-14 |
230 244 |
510 540 |
544 576 |
114 |
Nit/Blower,Heads,headers |
|
Crane |
104121 |
204 214 |
429 452 |
458 482 |
116 |
Near Stock |
|
Crane |
104141 |
218 218 |
498 498 |
531 531 |
116 |
|
|
Crane |
10HR00017 |
214 218 |
488 498 |
520 531 |
114 |
|
|
Crane |
|
198 206 |
480 480 |
512 512 |
112 |
|
|
Crane |
|
214 220 |
452 465 |
481 496 |
112 |
|
|
Crane |
104125 |
208 214 |
438 452 |
467 482 |
112 |
|
|
Crane |
104124 |
214 220 |
452 465 |
481 496 |
112 |
|
|
Crane |
109621 |
214 222 |
498 509 |
520 542 |
112 |
|
|
Crane |
|
215 224 |
499 499 |
532 532 |
112 |
FIS custom blower |
|
Crower |
LM-00402 |
219 227 |
498 518 |
531 553 |
108 |
|
|
Doug Rippie |
|
222 230 |
508 528 |
542 563 |
|
|
|
GM(Crane) |
12370846 |
222 230 |
509 528 |
543 563 |
112 |
|
|
GM(Crane) |
12370847 |
234 242 |
539 558 |
575 595 |
112 |
|
|
GM |
24502586 |
218 228 |
492 492 |
525 525 |
112 |
LT4 HOT |
|
GM |
|
|
450 450 |
480 480 |
|
LT1 stock ('93) |
|
GM |
|
203 210 |
446 449 |
476 479 |
115 |
96 LT4 (stock) |
|
GM |
|
203 208 |
450 460 |
480 491 |
116 |
96 LT1 (stock) |
|
GM |
|
205 207 |
447 459 |
477 490 |
117 |
94-95 LT1(stock) |
|
GM |
|
|
474 510 |
506 544 |
112 |
ZZ3* |
|
LGM |
N365 |
211 220 |
492 492 |
525 525 |
112 |
1500-6200 |
|
LGM |
N365S |
220 220 |
492 492 |
525 525 |
112 |
1800-6400 |
|
LGM |
N385 |
220 230 |
480 480 |
512 512 |
110 |
3000-6500 |
|
LGM |
N385S |
230 230 |
480 480 |
512 512 |
112 |
3000-6500 |
|
LPE |
74211 |
211 219 |
499 525 |
533 560 |
112 |
1600-5200 |
|
LPE |
74216 |
213 219 |
462 471 |
493 502 |
112 |
1600-5200 |
|
LPE |
74219 |
219 219 |
525 525 |
560 560 |
112 |
1600-6200 |
|
Lunati |
50160 |
213 218 |
446 468 |
475 499 |
110 |
1500-5300 |
|
Lunati |
50155 |
215 218 |
489 503 |
522 537 |
113 |
1500-5500 |
|
Lunati |
50156 |
232 242 |
510 525 |
544 560 |
108 |
2000-6500 |
|
Lunati |
50162 |
242 252 |
525 540 |
560 576 |
108 |
2200-6800 |
|
MTI |
|
210 220 |
500 510 |
533 544 |
114 |
|
|
MTI |
|
230 244 |
510 540 |
544 576 |
112 |
|
|
RRA |
1-215-224-A112 |
215 224 |
489 489 |
522 522 |
112 |
Jim Black |
|
SealPwr |
|
222 232 |
478 497 |
510 530 |
114 |
KenRahaim |
|
TPIS |
700-134 |
212 226 |
483 520 |
515 555 |
112 |
ZZ9 cam for 93-94 |
|
TPIS |
700-142 |
212 226 |
483 520 |
515 555 |
112 |
ZZ9 cam for 95-97 |
*Note the ZZ3 requires a longer camshaft dowel pin for use in 1995 and later LT1s (GM part number 10214485). However, the replacement pin requires that the pilot hole on the cam be drilled slightly larger (in depth and width) to accommodate the larger pin. Note also the hole is tapered at the top and the bottom. That is, at the face of the cam, it's 5/8" across, however, as you go in, the width narrows to 1/2". The depth is 1 5/32", however, the very bottom 3/32" is tapered inwards to a point. So if you have a flat pin, then it will only go in 1 2/32" since the tapered part won't be wide enough to accept the pin any deeper.
Q: What aftermarket camshafts are available for the V6?
A: The following 2.8L engine cams fit the '93-'95 3.4L engine:
|
Manufacturer |
Part # |
Duration |
Lift (1.5) |
Lift (1.6) |
Lobe |
Notes |
|
|
|
Int Exh |
Int Exh |
Int Exh |
Sep |
|
|
GM |
12363220 |
204 216 |
427 454 |
|
|
|
|
GM |
12353919 |
204 214 |
420 442 |
|
|
|
|
GM |
14031378 |
196 203 |
394 410 |
|
|
|
|
Crane |
254112 |
198 204 |
401 403 |
|
|
|
|
Crane |
254122 |
204 214 |
423 423 |
|
|
|
|
Crane |
253901 |
204 216 |
427 454 |
|
|
|
|
Crane |
253941 |
216 228 |
454 480 |
|
|
|
Q: What's that knocking noise when LT1 or LS1 is cold?
A: While the fuel injectors have a distinct tapping noise (usually under higher throttle), at a light load and low speed there seems to be "piston slap" on some people's cars. This occurs in some of the Corvette LT1s as well. There doesn't seem to be anything in the service manuals. Most dealers seem to acknowledge the problem and say it's normal, which it seems to be. For some reason, the pistons shrink enough in the cold weather so as to "slap" around a little. Once the car warms up, the noise should go away. This is also a noticeable quirk of the LS1. Some people's cars are more noticeable than others are.
Q: What's that ticking noise when the engine is under load?
A: It might be the EGR tube. It might sound like an exhaust leak from one of manifolds, but check for a possible crack in the EGR tube.
