Modifying your 3800 Powered Vehicle: Safe as Stock to 12’s or Faster…
I know Bio and a few others here had been talking about doing this and he can add whatever I might skip or miss here. Not that I am tired of helping people, I am just tired of posting the same thing over, and, over, and over again, as it feels like a broken record and no one seems to take into consideration there are some very vital steps to take before jumping into this pool head first in the shallow end. This is just my opinion over the few years I have learned and gathered information and worked on these cars and have build my own with the help of so many awesome people.
The first question here at hand is to see what year car you are going after. Modifying a ’97 Grand Prix is different than the ’98-’02 GP’s as well as the 2003’s are different from all the others too. Then comes the ’04-’08 Grand Prix’s. I know that there are PCM issues and would love for the ‘04+ guys to let me know what they are. Something about PCM’s not being compatible or able to tune, or something along those lines. Tuning the ’97-’03 Grand Prix’s are a bit easier as there have been way more extensive testing on them than the ‘04+ cars, even though they are still highly modded by many people as they are becoming cheaper and more readily available.
Basic info about them is that they are a FWD, 4-spd automatic transmission (Code-Named the 4T65E-HD; 2.93 gearing) 3800 Supercharged V6 platform (Code-named L67 or L32), rated at 240 hp/260hp and 280 ft. lbs. of torque from the factory. Figure your 20%-ish drive train loss and you’ve got your basic wheel horsepower numbers. The Grand Prix GT was also powered by the 3800 V6 (Code-Named L36 or L26) and mated to a 4-spd automatic transmission (Code-Named 4T65E; 3.29 gearing) making 200 hp and 225/230 ft. lbs. of torque. If you have just bought your ’97-’08 GT/GTP and are looking to modify it then please take these steps to insure safe modding and a reliable car down the road. Begin with your typical maintenance first, such as:
1) New Spark Plugs (You can upgrade spark plugs at this time if you wish)
2) New Spark Plug Wires (You can upgrade spark plug wires at this time if you wish)
3) Oil/Oil Filter Change
4) Fuel Filter Change
5) Coolant System Flush (Replace Dexcool with Yellow/Green Coolant)
6) New Thermostat (You can upgrade to a 180*/160* Thermostat at this time if you wish)
7) Lower Intake Manifold Gaskets/Coolant Elbows (2)
8) Transmission Pan Drop/New GM Transmission Filter (Replace 3-4 quarts with Dexron VI, not Dexron IV)
9) New Brake Pads and/or Rotors
Now, with all of that preventive maintenance finished, you can start modding safely, granted not all cars are going to need all of that but it will never hurt to get it done and out of the way. Now you can begin to mod your L67 Powered Car. Many comments I have gotten in the past as well as a lot of others are the poor souls who read 3800performance or ZZPerformance Tech Articles and “Stage Blah Blah” Performance Upgrades and think with a Intake, 180* T-Stat, and a Cat-back that you can safely run a 3.4” Supercharger pulley. Wrong. You can run it; it just is a ticking time bomb. See the KR Sticky Reptile wrote that explains how devastating Knock Retard can be to your newly found GT/GTP here: http://www.grandprixforums.net.....-1507.html (What is octane? KR? Explained here.)
Follow these steps to surely get the most out of your L36/L67 Powered Car. Keep in mind this is just how I would install these and prices are my guesses, so work with me if they are a little off…
1) Free Modifications - To be honest there is only one worth doing. Granted ZZPerformance talks all day about the TB Screen Removal, Voltage Booster, and even the Boost Bypass Modification…they aren’t worth it. They were put there for a reason from the factory; Leave it alone. The only one worth doing however is flipping your stock motor mounts. This can be seen how to do in Abrasive’s post in this thread here: http://www.grandprixforums.net.....13286.html (Dog bone flip?)
2) Cold Air Induction - Three Words; Make Your Own. People can argue all day about the K&N, Wizaird Intake, JMB Fenderwell, MSP CAI, SLP CAI, etc., but for the price they can all be beat if you take a trip up to Home Depot, Lowe’s, or your local Hardware Store. For the money it cannot be beat. The FWI out performs any intake on the market bar none. Streetwolf made a thread about how to build the best generic Fenderwell Intake System seen here: http://www.grandprixforums.net.....wi-20.html (Make A 4" Fenderwell Intake (FWI)[*])
Also, if you are not mechanically inclined, or lazy, like I am, check out TDC Racing’s Fenderwell Intake System. It runs a bit over $100 but is all mandrel bent tubing made specifically for the 3800 Powered Grand Prix ’97-’08 GT/GTP. Cost: $50-$150
3) Lower Temperature Thermostat - Easy mod for your GT/GTP as the stock T-Stat tends to run a bit hot, above 195*+. Throw in a 160* or 180* Thermostat from your local auto parts store to keep that motor cooler and run more efficiently. Cost: Less than $10
4) Spark Plugs - Change out those stock spark plugs with new ones to restore any lost power. Brands that most GT/GTP owners tend to go with are either Autolite or NGK Spark Plugs. Get these at your local auto parts store also. Others can chime in if they use something else. They range as follows:
Cooler the Spark Plugs, the lower your KR, but keep in mind, too cool of a plug will not always help you. 605/606’s are for a stock car, TR55/104’s are for small bolt-ons or basic 3.4” setups, TR6’s are for 3.25” Pulley range (Rockers, IC, etc.) and Autolite 103 Copper Core Race Plugs are for the extreme application 3.0” Pulley and smaller. Cost: $10-$20 appox.
5) Spark Plug Wires - If you need some new wires, opt for the stock Lifetime Warranty Auto Parts store brand, but if you want to upgrade and need new wires now is a great time. Companies that offer plug wires are MSD Ignition, Taylor, PRJ, ZZPerformance, and TDC Racing. All ranging from 8mm to 10.4mm monster wires. Cost: $60-$120
6) Exhaust - Here is where a lot of misconception tends to occur. Many people think that when someone says exhaust work that they can run 3” straight pipe from the cat back and drop to a 3.4” pulley and think that they have done enough exhaust work. Wrong. The cat back is the least of your worries as is flows good enough and has been dyno tested to not show signs of flow issues until 350+WHP, which is around 400hp at the crank. Exhaust modding should be done as follows:
Headers – If you have the money, just buy them up front. Installing headers means you don’t have to worry about the Powerlog, U-Bend, or Downpipe. Flow is unmatched by any other exhaust setup and there are many brands out there to choose from. I have Pacesetter’s and love them for the price. Headers are priced by quality for the most part, so if you have the money, buy some ZZP Headers or T.O.G. Headers. Cost: $300-$1,000
See Some Headers here:
Powerlog Front Manifold – The Front Manifold in the GT/GTP Exhaust system was casted very poorly from the factory. Replacing it with a high flow unit from ZZPerformance gets rid of that nasty stock manifold, lowers KR, and gives you a few more ponies. ZZ Performance
Downpipe/U-Bend Delete – One of the best mods for a GT/GTP you can do with basic hand tools as long as you spring for the bolt-in type DP. The Downpipe and U-Bend are both hands down the most restrictive part of the exhaust system on our cars. If you ever plan on buying headers you will either have to demod to install them or wait and buy headers to being with. If your modding is not going to be very intense or internal, then the PLOG/DP setup is right for you. ZZPerformance or Hogan Performance are the only places where I would get a Downpipe from. For you GT guys if you ever plan on Top Swapping your L36 motor or you GTP guys that have minor to mild bolt-ons, lean towards the 3” Downpipe, Catted or Race Pipe, that is up to you as there is no more gains in a de-catted car to one that has one. If you are a GT/GTP guy and want a cheap weld-in Downpipe...then go for the Shorty DP. GT guys tend to go for the 2.5” as being Naturally Aspirated you want a bit more backpressure, but the GTP guys, being blown, want to get rod of all of that air ASAP so you'll want more towards the 3” DP. See info in depth here: ZZ Performance
Cost: $89.99 - $200+
Cat-Back Exhaust System – If you are done with all of your other mods exhaust wise and still want a different tone, look into exhaust systems. You will not gain any sort of power increase from this, in fact, it is rumored cat-backs can harm these cars’ performance ratings. I won’t go into detail but there are many systems out there available. Prices are for pre-assembled bolt-in kits. Cost: $379.99+
7) - Tuned PCM (Performance Control Module) – This is hands down the best mod for the 3800 powered car in my opinion. One member here cracked a low 14 @ 98mph on a bone stock GTP with an awesome custom tune. A tune makes or breaks these cars so do not skimp here. There are only a few reputable companies left as many have closed shop or do poor tunes. Here is where I will say it again, DO NOT BUY ZZPERFORMANCE TUNED PCM’s. Their support is for the most part horrible, they will not refund you (I had to get the Missouri Att. General almost involved to get my money back) as I had to send mine back FOUR times and it was still wrong the fifth time, and keep in mind by GTP was my Daily Driver. It ended up toasting my motor a few months after having it installed (car had about 40K on it so there was no high mileage or neglectfulness at fault here), so in short, if you hate someone and want to give them a gift and they happen to own a 3800 Powered car. Get them a ZZP PCM. Otherwise, steer far away. The companies you can trust and many people have had great luck with is Will at Overkill Motorsports, Intense-Racing, or 3800 Performance, who sells the original Digital Horsepower Tuned PCM. Recently some members speculate that 3800 Performance sells ZZPerformance Tuned PCM’s but I have yet to see any proof of this. Other than mail-order tunes, you can buy a laptop tuner and go to town. Learning to tune is an awesome skill and will come in handy farther down the road. Digital Horsepower Inc. (DHP) used to be the only tuner available, but now since they have closed up shop; it is HP Tuners that is available. Another awesome program that I have yet to use. Get a tune. Your car will love you for it. A few things to note is ’97 PCM’s are not compatible with any other year as the same with the ‘03’s. ’98-’02 GT/GTP PCM’s are interchangeable. Cost: $100 - $700
So for the most part now minus the pulley swap you have run into a nice road block. Here is where you need to decide how far you are going to take your GT/GTP Build. If you would like to continue with just bolt-on performance modifications I’ll list the few more that are pretty basic.
1) ZZPerformance Exclusive HV3 Upper Insert (GT Only) – For you N/A guys this is a great mod. For the money it is said you will see gains of around 20hp or more and for a N/A car that is awesome. It is a very straight forward install also as all you do is remove the Upper Intake Manifold (Or Plenum) and place it inside of it. Comes with everything needed to install also. Cost: $200+
2) Ported Throttle Body – For both GT/GTP cars this is a great mod that will not so much give you a huge horsepower increase but will net you that lacking throttle response you’ve always wanted without having to drop a big lump sum on a aftermarket Billet Throttle Body or convert your car to a L67 Throttle Body, Northstar, or LS1 Throttle Body’d car. Throttle Body porting can be done fairly cheap too. If interested, shoot Reptile a PM on here. Same person who wrote the sticky about KR I had mentioned earlier. Does amazing work, quick turn around, and for the price…you honestly cannot compete. The butt dyno will love it too Cost: $50 + your Throttle Body
3) Ported Supercharger Case (GTP or Top Swap Only) – This is another great bolt-on mod which I stand by very much so, basically because there is nothing like hearing the blower whine A LOT more than it already does. Porting the inlet and outlet of the supercharger case not only increases flow capabilities of the supercharger itself, but also with the increased flow comes lower temps radiating from the case itself. This will not only increase horsepower/torque figures, but you will also be able to hear the supercharger whine more, or whistle more at idle, and since it dissipates heat faster, you are lowering KR levels at the same time. Great to couple this with a Ported Throttle Body at the same time. Again, PM Reptile on this one too in my opinion. Cost: $150 + your Supercharger Case
Now for you supercharged guys, here is the most fun part I think, the infamous pulley drop. Yes, more boost. Now that you have the mods to safely run a smaller supercharger pulley there are two options to boot. One is you are going to keep this pulley size or two; you are going to continue to mod your car and eventually go with a smaller pulley. As of now your best bet is a 3.5” or 3.4” Pulley. You should be able to easily run knock free with that size pulley. Keep in mind when you do drop pullies to maximize power, drop to a smaller supercharger belt with the sizes seen here taken from ZZPerformance:
060680 - ?Stage 2 intercooler 2.6 - 2.8" pulley
Gen 5 blower S3 IC 2.6"-2.9", S2 IC 2.7"-3.0" pulley
060685 - Gen 5 blower, stage 3 IC 3.0+ pulley
?Stage 2 intercooler 2.9 - 3.1" pulley
060915 - Stock accessory belt for '99-03
-also works with either UD WP pulley or OD alt pulley but not both
060923 - Accessory belt for 99+ with UD WP pulley and alt UD pulley
060905 - Stock accessory belt for '04+
060935 - Stock accessory belt for 97/98 (94")
060938 - Accessory belt for 97/98 with underdrive pulleys
060970 - SS M90 for 97/98
060950 - SS M90 for 99+
915 99-03 stock accessory belt
923 99-03 for underdrive water pump and Alt pulley
905 04+ stock accessory belt
935 97/98 stock accessory belt
938 97/98 for underdrive water pump and Alt pulley
667 stock S/C belt for GTP, GS, SS
658 GTP, GS, SS S/C belt for 3.5-3.25 pulley
650 GTP, GS, SS S/C belt for 3.2-3.0 pulley
721 stock Bonneville SSEi Supercharger belt
716 Bonneville with 3.5-3.25 S/C pulley
875 99-03 accessory belt with Meziere water pump
864 04+ accessory belt with Meziere water pump
895 97/98 with Meziere water pump
685 S/C belt s2/s3 ic 3.0-2.8 pulley (depends on tensioners)
680 S/C belt s2/s3 ic 2.7-2.55 pulley (depends on tensioners)
670 S/C belt ss ic with 3.2+ pulley
667 S/C belt ss ic with 3.2-3.0 pulley
1) - Press-On Supercharger Pulley – Just as the title states. This pulley is the same as the stock idea as the smaller pulley is pressed on the Supercharger snout with a special Pulley Tool that companies such as ZZPerformance rent out or for your best bet try to find someone that knows how to do this close to you to save you a load of money. You can buy them fairly cheap but I think no one should get them, just spring for the M.P.S. Otherwise, a great buy. Cost - $60
2) - Modular Pulley System – This another one of those “Must Have” parts for your Supercharged Grand Prix. This is an interchangeable pulley system that is offered by a few companies, such as the most popular ZZP Performance Modular Pulley System (ZZP MPS), Thrasher M.P.S., Pulley Boys Quik-change System, etc. Basically instead of having to take at least an hour of your time using a pulley puller tool to remove the old press-on pulley and press-on the new, smaller pulley, these quick changing pulley “hubs” allow you to swap pulley sizes in a matter of minutes with 5-6 Allen Head bolts. The kit you will buy most of the time comes with one pulley and everything needed to install them except for the puller tool. Cost: $100+ for the kit, depending on who you go with and $50+ for the interchangeable pulleys.
Now you have hit yet another big crossroad in the mod process. If you are still seeking more performance from your GT/GTP Grand Prix here are some of the big steps a lot of people tend to take. This includes: High Ratio Rockers, Intercooling, Camming, or Top Swapping. The following is what I have learned coming across going beyond bolt-on parts.
1) - Top Swapped 3800 V6 (GT Only) – Don’t cry you non-supercharged guys, there is still hope on how to lay a smack down on a factory supercharged car and that lies within your block. Yup, Compression Ratio. Higher Compression means a few things for you who go the top swap route. One, you will make more power on the same sized pulley as the factory L67 powered car. Two, High Comp. loves boost. It is easier to blow motors with too much boost and high compression but when tuned correctly is a very lethal combination that will beat most cammed and intercooled L67 cars. Here is the thread I would more than advise reading on the Top Swap (There is also a lot of great info in this thread too): http://www.grandprixforums.net.....-7763.html (Top Swap Info and Faqs, Also lots of 3800 Info) . This isn’t the easiest thing to do, nor is the hardest, you do have to tear the block down to the heads. Cost: $700+
2) - High Ratio Rockers – Thankfully GM made one thing simple…pushrod motors!! Stock GT/GTP cars came with 1.60:1 or 1.66:1 Ratio Rockers from the factory. There are a few choices that you have here to make some more power by letting those valves open more.
a) Modded Stock Rockers – ZZPerformance decided to elaborate on the efficient stock design for those wanting more performance on a budget. ZZP introduced the 1.90:1 Modded Stock Rockers. Basically, these rockers start out as stockers. The seats are welded in and ZZP re-machined them to achieve a ratio of 1.90:1. Great and easy way to add about 20 horsepower without having to change valve springs. As long as you keep your shift points at or below 6,000 RPM you will be fine. Anymore and the stock valve springs tend to float. Cost: $275+
b) Roller Rockers – If you want to upgrade your valve train and have the money to do so and are going the rocker route then Roller’s are right for you. Roller Rockers are a lot lighter and are much easier on the valves than the stock or Modded Rockers, but come at a price. Much more expensive than the Modded Stock Rockers for about the same performance gain. Roller’s come in the ratio of 1.60:1, 1.70:1, 1.80:1, 1.84:1, 1.90:1, and 1.95:1. Anything higher than 1.84:1 ratio is going to be needing valve springs to compensate for valve float as long as they are shifting higher than 6,000 RPM’s. LS6 or L76 Springs are great and cheap for this upgrade, but you will need retainers too. These are a great alternative to a cam budget wise and you still retain very stock drivability and some have even reported better gas mileage. Keep in mind you will benefit even more from a custom tune afterwards. Also remember that if you ever go cammed you will have to sell the rockers as you can only run stock 1.6 ratio with a cam for the most part.
3) - Intercooling – This right here is probably another one of those, “If you have the money, BUY IT” mods. Proven to be the best knock killer in most cars along side Methanol Injection. Available to you are the Short Stack Intercoolers, Stage 2 Intercooler, and Phenolic Stage 3 Intercooler. All doing the same thing, cooling the compressed air from the supercharger and shoving all of that cooled air into the motor for a denser charge. For anyone planning on going the IC route, let this be known. Skip the Short Stack. Save your money and buy at least a Stage 2. The Short Stack is half the price, but you get what you pay for. They heat soak very quickly and are just not really thick enough to do any good. Obtaining a Stage 2 or 3 IC will allow for a 3.2” or lower pulley drop on a basically stock car. This was the idea back in 1996 in the concept car GPX, but GM didn’t go through with the design, which was in my opinion a huge mistake as it would have made the GTP a VERY fast car. Also keep in mind that if you do happen to get away with dropping lower than a 3.1”/3.0” pulley, your stock fuel injectors will probably run static (out of fuel) and you’ll need bigger injectors. Also to run along with this is the kind of IC Pumps and Heat Exchangers you will buy. This is honestly up to you, just I’d just go for the bigger H.E. you can find and the GM Pump as it might run you more but will never break down on you. Cost: $600+
4) - Camshafts – Camming your GT/GTP is one of those advanced level mods. It entails either doing it while your motor is out by pulling the balancer and front cover and a few other small things, OR, Dropping the motor mount and pulling the cam out through the wheel well, which is a nice alternative for those not comfortable with pulling the motor all the way out. There are many choices of cams out there. Read this sticky here for all of that information: http://www.grandprixforums.net.....s-747.html (Cam specs?) . Further discussions have gone on in other threads and you can ask about them in a new on or read many of the previous ones about the different cams for the 3800 enthusiast. Cost: $300+
5) - Pulley Drop – Yet again you supercharged guys have the chance to drop pulley size yet again with rockers, intercooler, or a cam. The most popular pulley to drop from after the 3.4” is the 3.25”. Some of the intercooled guys go smaller but it really isn’t needed if the car is tuned right. Also, dropping lower than a 3.1” pulley will run the stock #33lb. fuel injectors static and you will need to upgrade to #42.5lb. Injectors…#60 ones are way overkill. Cost: $50+ for the pulley, $250+ for Injectors
Now most people would be running out to the track to go beat the crap out of their new found power. But, here comes yet another weak point in the Grand Prix modding process, the transmission. Most people with lose the 4th Shaft first, or shred differentials all together. From what I have heard, ’97 GTP’s have harder input shafts, but don’t quote me on it. ’97 GT cars should be steered clear from. If you plan to mod and have not bought one yet, don't. They use a very weak vacuum powered transmission that is prone to crapping out quickly after you top swap them or heavily mod them and beat on them with just the N/A motor. ’97-’02 GTP’s use the 4T65E-HD Transmission with 2.93 gear ratios which are great for highway mileage and ¼ mile runs. The ‘03’s were supposed to be changed to the ‘04+ body style but GM didn’t get around to doing it then, so the ’04 transmission was thrown in all '03's. It had the Hardened 4th Shaft which most people upgrade to in built ones from the factory and it had a completely different valve body which makes them harder to tune and not compatible with any other year PCM’s, all from the factory. Mine being a 2003 year model, I saw numerous sub 1.9X 60 foot times at the local drag strip and I shredded a differential just once. Everything else in the transmission was fine, when I tossed it. Surprisingly it took that much abuse, it served its purpose and I upgraded to the ONLY transmission you should ever consider for your ‘97+ Grand Prix…a Triple Edge Performance Transmission. See Dave here at: Triple Edge Performance - Home Page .
Not only is he a great guy, he has great customer service and his slap-bang, crazy ass transmissions are AMAZING for the price and quality. And if you happen to be in the Midwest around the Kansas City, Missouri area and don’t feel like driving all of the way to Indiana for a transmission install, Green Bastard Products will install it for you as they are Certified Triple Edge Transmission Installers. GBP Inc. is who installed mine and I got to work on the first ever local transmission install (Brian's transmission he won at the 2007 BGPM)…sure was time consuming but I learned so much from that!! After the install, get her all ready to go and hit the track. With Dave’s transmission built to spec you can be pulling 1.6-1.7 60 foots all night long with slicks. Talk about dropping time off your 1/4 See a little bit of Dave's work in action here... http://www.youtube.com/watch?v=XdklbR98OyM
I know for sure there is probably way more info out there but I wanted to cover the basics and give a little info for the people after that. I know I am no expert and I know for sure I didn’t cover tuning, engine accessories, suspension, brakes, etc. But I just wanted to get across the typical 3.4” or N/A setup and beginning mod list of the average 3800 enthusiast. Hope you guys get enough info out of here as I took the time to write it and we won’t be getting AS MANY…”Hey I just got a GTP and put a 3.4” pulley on it…what should I do next?” threads Just read, read, read…that is what has helped me learn everything I have and one last thing…have fun with it. Mod safely and you will have a fun DD, track bruiser, or both and the best part it they still get great MPG’s and can haul 5 people while the Corvette you might be walking away from can only hold 2!!
I also disagree with the plugs comment, your stock ones will be fine way into high HP. upgrade only for the looks haha
I noticed a big difference in knock when I went from the stock plugs at 65k miles to copper core plugs. The stocks just aren't cold enough when you start pushing the limits on timing advance.
What were your mods at that point?
Don't even remember. Plog, HVTB, DP, WIzAir, and the Powrtuner.
My apologies, I meant wires!!!! haha
In that case you're right. I would still recommend getting PRJs if you will be modding a lot. The stockers come apart sometimes on the first time you try to remove them. PRJs come off easy and are nearly indestructible so you will never need wires again.
I agree with the PRJs being great for modding. I'm planning on removing the plug wires at least one more time (power log install) and maybe an HV3. I figured it's easier to pay more up front than worry about wrecking wires later.
Protip: If you don't know what you're doing, don't do it.
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