Thread: Newbie to the s/c 3800 world......need some expertise from u guys

So i aquired a 1998 GP GTP about 3 months ago and have been very impressed with it.....I took it to the dyno this evening and was kind of dissapointed in the results. Just going by some of the posts i have seen on this forum i was expecting a little bit more with the mods that it has.

It made 199 whp and 250 wtq

Here is a list of the mods that it has that i know of:

Pacesetter headers with down pipe
MSD coil packs and 8.5 mm wires
3.4 modular s/c pulley
Mezeirre electric water pump
the fuel pump resistor delete {or something like that}
alt. voltage booster
flowmaster mufflers
basic ecm mods (egr code delete, fan on of temp for 160 deg thermostat, fan run time of like 3 mins after shut off)
160 degree thermostat
some aftermarket gauges....showing that im making 8lbs of boost (which is what i thaugh they made with a stock 3.8 pulley???)
Northstar TB swap
K and N intake tube and filter

As far as i know it dosent have any internal mods or even a tune on the ecm for the smaller pulley.

The car has 114k and has been VERY well kept....I believe the S/C is the original, but has had just the snout replaced recently, but still with original rotor pack

Let know what you guys think about my dyno numbers and if that seems accurate....Just seems like a lot of money for someone to throw at it for some numbers like that

I would suggest a tune, some of the other guys on here can probably fill you in more, but from what ive heard, if you have all those mods and dont have a decent tune, there almost worthless.

I recently got a tune from will at overkill and it really woke the car up and I am still on a stock pulley.

The kr im not sure of.....I have ordered a interceptor gauge..I was hoping to have it before my dyno appt....Im not having any detonation issues. While it was on the dyno it did start getting close to the lean side of things...I know im gonna have to get a tune but as far as the boost press on the 3.4 pulley at 8lbs, is that about right? i know one guy said he was making 11 with that..i guess what im getting at could the rotor pack be worn or is it that low because the motor is flowing well?


Another problem im gonna have her in GA is finding a good tune shop....the one i deal with for my stang dynoed it but he dosent do gm tuning....we have some vette shops around atlanta, think they could tune tha gtp for me?

Either the motor is flowing well or the blower rotor coating is missing.

Seeing the dyno printout would be most helpful at this point.

Also curious if your car has a cat on it, and if so, what kind.

i will scan it and put it up......No the cat has been removed and i did see in some paper work that the guy had the rear o2 deleted out of the ecm....it does have the resonator on it still as well

Got the interceptor gauge today, and first thing i went and checked was for kr. According to the gauge i have absolutely none! I check ign timing as well and its showing that its staying advanced 15 deg at WOT. As far tuning, do any of you know of anywhere here in Georgia that does GM tuning?

nah i dont think im drowning. When it was hooked to the wide bandon the dyno it was around 12.4 on the A/F ratio in the upper Rpms....As far as the MSD coil packs, thats the second time in this thread ive heard that....lol whats recommended? Stock?lol

Originally Posted by jdmgtp

with numbers that low and inconsistent as the ones on the graph you can be certain it needs a tune.

Uh?

While your numbers are "low"... It could just be the dyno... I wouldnt base anything off of that.

Its clear that your afr's are probably decent assuming you have a cat converter... They typically take things about a point leaner. You are probalby too rich if anything, but on a non IC setup that is ok.

Timing is a bit low for a clean setup like that. I would suggest 17 or 18, which could give you up to another 15-20whp. The MSD delete and some fresh al104 plugs may help a bit as well.