• The site migration is complete! Hopefully everything transferred properly from the multiple decades old software we were using before. If you notice any issues please let me know, thanks! Also, I'm still working on things like chatbox, etc so hopefully those will be working in the next week or two.

3.8 performace rebuild questions...

C

Chris Peterson

New member
Is there any good write up on a 3.8 supercharged engine rebuild? Just purchased a '99 GTP with 170,000 miles on it. It runs well and is still powerful but I want alittle more. I've built a couple of AMC V8's to 460hp and ported heads etc etc.

I'm also wondering if anyone has opened up the chambers alittle in order to run more boost with a little lower compression?

I am thinking of going threw the motor and get it freshened up for more power. Such as a cam, intercooler, headers and ported stock heads and supercharger. Looking for 350 to 400hp if that's possible and keep the streetablity and killing the MPG to badly. I don't want to turn the motor nine million RPM to make the power. Would like to be able to run a mix of E85 or just straight E85 if I want.

I used to drive a '99 Grand Prix SE 3.1 and mixed unleaded with E85 almost 50/50 without a engine light. In the GTP I get a system lean code and I have backed off the E85 now. Is the 3.8 more picky or did someone mess with the tune?
 


If you haven't read this thread yet, do so and it may help answer some of your questions on these cars.

http://www.grandprixforums.net/safely-modding-your-3800-powered-car-17482.html

FYI, leave the bottom end alone (don't replace rod and main bearings) as they are known to die shortly after rebuilds due to the fact that most people don't have the block line bored and checked before reassembly. Also keep in mind that rod and head bolts are TTY and are not reuseable. I'd go with ARP stuff if you are in that far.

If you aren't scanning for KR while mixing the E85 in the GTP then you are asking for a rebuild sooner than later. These cars like to chip pistons if not tuned correctly.
 
M90 is a terrible power adder, if anything, you want more compression if you plan to keep using it.

That idea is better suited to power adders capable of higher pressure ratios.

This forum in general won't be very helpful in making that much power.

If you really plan do all of those things, mid/high 300's at the wheels is within grasp.

Building a trans to hold that, and finding the right suspension/tire combo will be the fun parts.
 
dont run E85 without a tune, thats silly. you wont be able to take advantage of it at all without a tune, and you have a good chance of popping a piston at WOT.
 
You must log in or register to reply here.
Back
Top