2004 Grand Prix GT question

[rynmcdonald]

I have a friend that owns this car and when I drove it, I noticed it has significantly stronger pull than my 2005 SLE. I am wondering if I can get that kind of power with mine. His is DBW whereas mine is DBC. Would this make a difference? I’ve often wondered if I have SC heads on the car for lack of power.

[harofreak00]

In my experience, DBW makes it feel a little laggy...opposite of what you're feeling.

SC heads have the injector bosses in the head themselves while the NA has the injector bosses in the lower intake manifold. They are not interchangeable.

Have you raced them side by side? It might just be in your head? They should be nearly identical performance.

[95naSTA]

If the GP has a 3.29 and you have a 3.05 FDR, that could be the bulk of it.

[rynmcdonald]

The vehicle was bought from a college off of GOVDEALS.COM

Tennessee College of Applied Technology Morristown. Car had 92,820 on it when I got her. Now has 105K. Soooo I don't know what all was done to it. The students kept it well maintained. I have since changed the trans filter and put DEX VI Mercon in it.... bottle said that it was safe to add it to DEX III. Changed the plugs to NGK Platinums... has AC Delco wires. Updated the coil to L67 packs. Running Mobil 1 full synthetic 5W-30 with a Wix XP filter. Purged the coolant and added a stronger concentration ... 60/40 mix.

My wonder is if I need to get into the transmission and put new clutches in it along with a shift kit, rev-bang spring and solenoids. Torque converter wouldn't be a bad idea either
BTW harofreak00..... that Bonneville you have pictured has the same front end as mine

[rynmcdonald]

200… 200 FREAKIN HP Is ALL this SLE (slow lazy excuse) of a car HAS?! Would like to know something as to how to get it up there with the SCer ranks or close to 300. Fuel economy would be relatively untouched I hope. Not gonna have my foot in it ALL the time. But that stock power is *shoot*! I see V6 now making close to 300 or more getting close to 30 MPG

[95naSTA]

Lol. Welcome to a pushrod engine that came out in 1995.

Search top-swap or get an SSEi or get a newer car.

You can't get anywhere near 300 crank hp without a supercharger, turbo or nitrous. I have probably seen every public n/a 3800 dyno of any significance from the past 20 years.

[luke_dubs]

200… 200 FREAKIN HP Is ALL this SLE (slow lazy excuse) of a car HAS?! Would like to know something as to how to get it up there with the SCer ranks or close to 300. Fuel economy would be relatively untouched I hope. Not gonna have my foot in it ALL the time. But that stock power is *shoot*! I see V6 now making close to 300 or more getting close to 30 MPG

It's built to be reliable and fuel efficient - but is only fuel injected. The modern V6 engines have direct injection, VVT, better computers that can vary different aspects of the engine to allow for more mpg or better performance.......not to mention transmissions with more gears, so they're able to make more power as well as good fuel economy.

You're better off swapping an L67 in place of the current engine if you want more power - the n/a 3800s are really sturdy but not really built for forced induction.

[nos4blood70]

His GP might be one of the later ones with the supercharger on it.

I would not modify this car for more power, it is a cash rabbit hole with small gains, hampered by a weak slush box transmission.

Enjoy the car for what it is... a comfortable, easy and inexpensive to maintain daily driver. If you keep it out of the salt, or at least undercoat it, you should enjoy it for years to come.

Get a different car for fun stuff. I almost turbocharged my SLE and I am so glad I did not and instead saved money and got an S2000 along side of her.

[rynmcdonald]

I believe 95naSTA is running 10.5:1 static compression on a NA engine. What kind of power that making?

[luke_dubs]

If it was one of the newer Grand Prix's, then it got 260 hp from its Series III 3800. Wouldn't surprise me if it felt much faster, even if the torque figure didn't change between the L67 and that 260 hp L32.

[95naSTA]

I believe 95naSTA is running 10.5:1 static compression on a NA engine. What kind of power that making?

That CR plus every other n/a mod but I never had it dyno'd. I would like to see 250whp, especially since I have a manual trans but I won't know until I strap it down. That will probably be a while. What I did makes absolutely zero sense hp/$ but I wanted to see how far I could get n/a.

[nos4blood70]

Non factory boosted 3800s can take boost just fine. In fact, most people prefer the higher compression, it makes more power.

Regardless, NA 3800 record is somewhere in the 260 or 280 whp range and that is with throwing the kitchen sink at it. It just doesn't flow very well.

Once you boost it, you can make some power, but the transmission will ruin everything for you. And even then, you're still stuck with a FWD platform.

95Nasta's car is super cool. All about the custom build, and I bet it is way more to drive than any boosted auto 3800 no matter how powerful. It is more about the experience.

This is the wrong platform for performance. You're 20 years late.

[camopaint0707]

are we measuring this with a butt dyno?

[rynmcdonald]

What about taking and transplanting one of the 60° V6 engines like the 3500, 3600 or 3900 into a bonneville with the transmission that is mated to it? Kind of curious if that has ever been done. You would have the power and the extra gears.

I seen a Grand Prix at the wrecking yard… Or maybe it was a G6 and was a GTP package… Yet it had one of those three 60° V6 engines, yet it wasn’t super charged

[95naSTA]

It's never been done on this forum likely because it's cheaper and easier to get more reliable power from a 3800. Anything with variable timing or DBW would likely be harder to integrate as well.

60*v6 engines are more modern as far as pushrod engines go and can flow much more but have suffered far more engine gasket failures than 3800s. It was a cool community to watch in the mid/late 00s with how modular the engines were. 3500 swaps and top swaps were popular and made a lot of smaller late 80s/early 90s cars quick.

[nos4blood70]

It isn't worth it for multiple reasons. Those engines don't develop significantly more power and the costs are prohibitive. The mounting points are all different, and you'd have to make the PCM talk to the rest of the car and accept the 5 or 6 speed transmission.

These cars are best enjoyed in their stock format. Especially for someone without any fabrication skills.

I remember going through this weird heartbreak earlier on in my ownership, especially with other friends in faster or more modern vehicles.

Your best is to get another vehicle as a project or fun car, or move to another more modern platform... Something that comes turbo from the factory for easy gains.

I've been on this forum and other 3800 forums and Facebook groups for over a decade. People always come in upset with the factory power output, then they mod the car with various degrees of success. In this age of turbo cars and EVs, it would be super hard to make a Bonneville fast and competitive. It's more than likely going to become a money pit that ends up in the junkyard before its time. I was almost that guy.

I still dream of a 2000+ Bonneville with a turbo 3800 and a more modern 6 speed auto, or better yet, a 6 speed manual. Truth is, it's very hard to get it to work, especially in a reliable daily driver type of fashion.

[Ramcharger310]

My guess?

1. Final drive ratio
2. Less weight.