Thread: 04 GTP questions, seeking mod advice

Been lurking a long time, time for me to finally post. I picked up a 2004 GTP Competition Group about a month ago and have been doing maintenance and minor repairs in preparation to begin mods. It has 161k miles. I have a mod plan but would like a second opinion since I have the Series III motor and most advice on the web is for Series II. My budget is to stay under $1000, this is what I am thinking:

-Exhaust work. Thinking ZZP front powerlog + 3" catted downpipe. I want full headers, but the only thing in my budget would be speed daddy headers and I don't have the skills to weld in a cat and figure out how to hook up the O2 sensor. Yes, I MUST have them because emissions are required where I am (Utah).
-Canned PCM tune. I would like advice on which is best. From what I have read, people generally are happiest with Overkill and Intense tunes.
-3.6 or 3.5 pulley, depending on how hard it will be to eliminate KR. I currently have 5-7* KR at WOT around 5000 rpm with engine warmed up and ambient temp of ~45 fahrenheit.

I have already done gutted stock airbox and Autolite 104 copper plugs, as well as a mild shift kit. Tried to do 180 thermostat, but bolts are seized and I'm not interested in having to drill and tap new holes in my intake manifold after I break them.

I only have access to 91 octane gas where I am, haven't seen any stations selling 92 or 93. No E85 either.

So if anyone has any suggestions for different mods or how to make these work better, please let me know! I am new to modding and I can't do anything radical since this is my daily driver. I just want to have a few more ponies and make up for the lost performance from living at over 4000 feet of altitude lol

I wouldn't drop pulleys. I believe SD headers come with a V flange that clamps to the cat and to the flex, there should be no welding necessary.

The thermostat bolts are deceptive. The actual bolt is like an M10 with an under sized head to prevent over torque.

Also, those plugs are too cold.

I doubt with the mods you listed that you'll be able to drop pulleys.

Without access to e85, your biggest bang for the buck would be saving for a cam or intercooler. Actually, I'm pretty sure you could buy a downpipe, intercooler, and 3.4 pulley and still be under your $1000 limit.

You really need to get that 180 degree thermostat to continue further Mods. It will help with knock. You will never get an answer from Overkill on the PCM. I used a ZZP tune and hand no problems with them in my 04 gt and Comp g. I changed to an Overkill and it was better than ZZP setup wise. I have all of 04 Unlocked on my HPT if you want to work something out. Otherwise if I were you I would get an HP Tuner. You can do a lot with it and be able to get your car tuned properly. which in turn will give more power, better acceleration and shifts. As well as disable codes so it will pass inspection.

Front plog would be ok but probably not needed unless you plan to mod further. You need to careful with a stock transmission as you mod.

I would do-
HP tuner or custom tune
180* thermostat
2.5 Downpipe.
NGK TR55IX plugs- you can stick with the 104s if you wanted
high flow air filter
3.6 MPS if you really want to drop pulleys. Must be tuned well.
Fuel pump rewire.
Plog if cash flow permits.

Having these things will allow you to mod in the future and have the tuning ability to do it properly.

Originally Posted by industrialfish

They are 2 heat ranges below stock on a basically unmodified car. Too cold can result in carbon deposits on the tip that won't cook off during normal operation, which can cause a hot spot, resulting in KR...

You want to run the hottest plug you can get away with.

True; however if you can run the colder plug (like I did), it isn't hurting anything.

Hell I had over 20k~ miles on AL103's and everyone always likes to complain that there isn't any life in them.

Run the 104's; gap them @ .050". Enjoy.

Hah; I'm probably not the best person to reply on that but I ran a totally stock fuel system on E85. Only thing I had done was the tuning (By Reptile), a couple fuel filter changes to make sure there wasn't anything clogging up since the car had over 280k on it, and lastly just green top Ford injectors (42lb.). Was a '98 GTP with a 3.2", GenV, Ported L67 TB, 3" catless DP, Open Cone intake, bone stock everything else.

As for putting together a kit, I'd venture to say that the E85 would be better than the intercooler, but that's me.

You'd be pretty well off tuning, pulley drop with headers, and springs/rockers. That'll toss your car right around 260-270WHP with say, a 3.5"/exhaust/rockers. E85 should put you in the 3.25"~ area...cranking timing as well...I'd say close to 300 at that point. These however are torque motors...they're not gonna grab your junk on a horsepower rating. It's pretty depressing most of the time.

Originally Posted by blueguy91

Hah; I'm probably not the best person to reply on that but I ran a totally stock fuel system on E85. Only thing I had done was the tuning (By Reptile), a couple fuel filter changes to make sure there wasn't anything clogging up since the car had over 280k on it, and lastly just green top Ford injectors (42lb.). Was a '98 GTP with a 3.2", GenV, Ported L67 TB, 3" catless DP, Open Cone intake, bone stock everything else.

As for putting together a kit, I'd venture to say that the E85 would be better than the intercooler, but that's me.

You'd be pretty well off tuning, pulley drop with headers, and springs/rockers. That'll toss your car right around 260-270WHP with say, a 3.5"/exhaust/rockers. E85 should put you in the 3.25"~ area...cranking timing as well...I'd say close to 300 at that point. These however are torque motors...they're not gonna grab your junk on a horsepower rating. It's pretty depressing most of the time.

I forgot about the rockers. Those are probably the best bang for your buck, other than a cam!! If you go E85 make sure you have a Tuner. I had issues with an E85 setup but it turned out to be a pcm going bad. I would contemplate doing it again but the fuel filter on the 07 is internal. The best bet for buying HPtuners is look at the HPT forums and look for someone that offers free training or support. Otherwise any vendor is ok. There are also some basics in the Tuning section to get you started.

*** I just read you dont have e85 option so forget those suggestions. lol

BTW. I will put a shameless plug here. I have a basically new AC Delco fuel pump for the comp g if you ever need one.

yes you need at least 42# injectors and if plan any further mods 60#. You will need a fuel filter. change it after a week of running the E85. You shouldn't need exhaust work. Downpipe helps. 180* thermostat, smaller gap on plugs, with no other mods I would think 3.6 maybe 3.5 with a proper tune.

Okay, thanks for the help everyone. It was very insightful! I'll go do some research and start pricing out parts to see what works best for me.

Originally Posted by rickisrad

yes you need at least 42# injectors and if plan any further mods 60#. You will need a fuel filter. change it after a week of running the E85. You shouldn't need exhaust work. Downpipe helps. 180* thermostat, smaller gap on plugs, with no other mods I would think 3.6 maybe 3.5 with a proper tune.

I'd recommend exhaust work on ANY 3800...of any level of modding.

It's god awful. The catback is fine; but everything else needs help. Manifold casting is crap, the downpipe is tiny, and the U-Bend is even worse.

On a stock car, PEM's and a 3" downpipe would probably add 15-20~ horse...and most of that would just be killing all the KR.