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98 gtp

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chuck1718

New member
I bought a 98 gtp with 3800 sc v6 recently and have some question. I want the car have more power than the stock and Ive read alot about what it takes. I have a local guy that is great at tuning but I need to know these things. I am going to buying some speed daddy headers will that cut out the stock u bend? Is there any CAI kits that are worth it or should I just use one of the dyi guides? Also think about getting some.different ratio rockers but really dont know what to get. So givin all this ill have headers, no u bend, rockers, 180 stat lower temp plugs, no cats and probably straight pipe tbh, and if someone can point me to some decent rockers chalk them up. What size pulley should I put on my sc? Of course then I will have my guy tune it. With all this done will the car still be very dependable? I will want to drive it to work and maybe on a decent mileage trips. What kind of mpg would yall think I would get under normal driving? Thanks for reading this and I hope to hear for everyone on their thoughts thanks again.
 


You'll regret straight piping the car. It's loud as hell and sounds like trash. Honestly, with headers and rockers (1.9 ratio), I'd go with a 3.4 pulley and see if it knocks. If not drop a little farther. One of the mods you need is a way to scan for KR. I'd looking into a scan gauge 2 or aeroforce. Dependability has far more to do with driving habits and maintenance. For example, I dd a 400+ whp turbo 3800 but, I don't launch the car at every stoplight.
 
theres nothing but a huge cam that would maybe stop you from daily driving these cars.

i got a hi comp block, fsic, 3.2 pulley, 42 lb injectors, diy ported heads, 1.95 yella terra rockers and drive it all over.


lots of guys will cam it with out a built tranny, but the tranny will take a crap in one way or another much sooner than later with a cam installed.

so plan on a built tranny if you want that much modding.


your starter mods are headers a diy intake, and a 3.4 pulley with a tune.
 
Scottydoggs said:
theres nothing but a huge cam that would maybe stop you from daily driving these cars.

i got a hi comp block, fsic, 3.2 pulley, 42 lb injectors, diy ported heads, 1.95 yella terra rockers and drive it all over.


lots of guys will cam it with out a built tranny, but the tranny will take a crap in one way or another much sooner than later with a cam installed.

so plan on a built tranny if you want that much modding.


your starter mods are headers a diy intake, and a 3.4 pulley with a tune.
Click to expand...
The smart money is with Scott as far as a tranny. If you want big power you need a built trans....

Unless you're drive like a normal person. I've been cammed over a year. Still on stock trans, only shift kit and a few things In the tune. Don't drive like an idiot. It'll last.

And go with a 3.4 with headers and rockers.
 
Okay thanks alot Im going to do what you all recommend and get the headers build a cia the pulley and my tune. Now my questions are with the sd header do I need a u bend delete? Will I need the new plugs and a 180 or 160 thermo? Also if you could recommend a pulley since I have never owned a sc Im lost. Without the pulley im looking at about 700 for headers cia and a scan gauge II I'm not wanting a "racecar" but I want to be able to do a dig race or two every couple of months against some stock 5.3s. How would all thisnaffect my mpg i know if its full throttle wont be good but say cruising 55 or 70? Thank again fornall the help.
 
A good tuner will increase your cruising mpg. You're not doing anything radical so I could see 28-30 mpg if you get someone to load you up in timing in your cruise cells.

Al104 copper plugs. Gapped at .050 or so. 180 thermo get it tuned for your fans to come on them too.

Rent a pulley puller and get a zzp mps with 3.4 pulley.
 


Stock thermostat, no need for a 180º. It's a pointless mod people think they need to do.


Headers are only 250 bucks after you buy better clamps, unless you want ZZP headers.

Everyone says buy a 3.4 first but most cars will still show spark knock with it, 3.5 or 3.6 is my starting point.

Gas mileage will not change if you drive it like an normal person.
 
Alright thanks guys if it helps with the thermo argument I live in very hot summer most days are 100+ with high humidity. So this is my shopping list http://zzperformance.com/3800/modular-pulleys.html http://speed-daddy.com/stainless-ss...r-exhaust-grand-prix-gtp-regal-impala-3-8l-v6 plus the plugs and tune thats 20 shy of 800. Of course ill do cia first headers and then slap my pulley on the day of my tune. Any other suggestion would be great can I lower my car with these headers? Thanks again guys.
 
What difference in psi would 3.6 3.5 or 3.4 make i know 3.4 makes most boost but is it 10 for 3.6 12 for 3.5 and 14psi for 3.4 top of the head numbers. What would that boil down to power wise? Yall are awesome just so you know.
 
Stock is roughly 7-8 psi depending on feet above level and DA etc etc.

Add headers and PSI drops because of more exhaust flow, boost is a measure of restriction. I had a 3.6 with headers and made 8-9 psi peak. A 3.5 might be around 9-10 and 3.4 10-11ish depending on all those other factors. Numbers could vary by 1-2 psi easy.

With a proper 3.4 setup might gain you 30-40whp in perfect conditions. Stock is around 195-200whp (you lose 40hp through drivetrain loss).
 


180° tstat is great for keeping the engine cooler in traffic on hot days. It also does a nice job of keeping the trans cooler.
 
~10º cooler isn't enough to make a difference for me. Is the part cheap, sure but it not going to do anything world changing and thus not something worthwhile.

I may not ever put alot of miles on my vehicles but that doesn't mean I haven't driven them hard or in very muggy/hot weather. I made sure my cooling system was up to par and never had cooling issues. Staying around 195-200 is prefectly fine.

I know I jump to the LS V8 motors sometimes for comparing here but many of those iron block motors that create even more heat and power has no problem running coolant temps around 190-200º. Infact if you are running a GEN 4 V8 computer with a stock OS you can't even adjust the fan settings to work with a 180º or 160º thermostat.
 
Lots of people see engine coolant Temps 230°+ in traffic with the stock tstat. Not an issue, but it's also not leaving you with much headroom. With 180° tstat, I never saw coolant temp about 190°. Trans Temps stayed below 180°.
 


Fun fact, I had one of my radiator cooling fan relays go bad last week. How did I know you ask?


I have a 180* thermostat. When I hit 210, even in 95+ weather I knew something was wrong.
 
Okay I think I will get a 180 even if it doesnt help anything but my peice of mind. I get stuck in tons of traffic and its like 110 here atm. I have a 96 4.8 ls1 in a short bed truck and it loved having heating problems til I drop in my 160 because traffic. We dont get much winter so Im not to worried about how fast it gets to temp. Thanks alot guys I got my flexplate fixed scanners on its way along with a new coupler for the sc. Thanks again guys and gals!!
 
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