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but I was going to get it done while I was removing the old headers to change out the exhaust manifold gasket why not go ahead and get it done check it off the list

Because you'd have to do the work all over again when doing the topswap. The headers would have to come out before removing the old heads. And you'd lose performance while NA. Pointless.

Because building an effectively modified car isn't just checking parts off the list. It's making the best combination of the available resources. Headers aren't part of that best combination for your car, that money can be spent elsewhere. Gaskets are $40, and the labor is a little more. Putting headers on a FWD Bonneville is a royal bitch, one very few shops want to tackle, and most DIY'ers bitch and moan about like none other, because they're not made for the car. Then come the issues with the cheap headers of bad clamps, leaking joints and other problems, or having to drop $6-800 on the "good" headers that still have the potential to leak or have issues. Then you have to go to an exhaust shop and get them connected to the rest of your exhaust.

How far out, realistically, would you top-swap? If it's a couple months, that's one thing. If it's a few years, then not only is it not worth it now, but the top-swap won't be worth it when you get there.

I wouldn't even do it if it was a couple months. It's still silly to be putting headers on an NA car before top swapping.

3 years ago I built a 1982 Buick Regal, replaced the 3.8 with a supercharged and blown 350 backed with a th350 turbo transmission and a ford 9" rear end. I had built that motor from the ground up. Gave it to my dad for his 60th birthday. He had bought it brand new, then scraped it after a collision. I bought it from the scrap yard and rebuilt it. During a car show drive, he was t-boned at an intersection by a lowered Chevy pickup. The motor and the car was trashed and it went back to the scrap yard. I want to start another build but everyone wants way too much for a donor car around here.

Its either building the Bonneville up, or buying a Kenworth w900 as a project. The Bonneville build might help other guys on here solve some questions. I don't debate this will be hard or even plausible, I want to do it because I can. I know its not out of the question to 500 hp out of one, the grand prix boys are doing it with the same motor.

500 is definitely possible. But you would need a turbo to accomplish it.

Possible, but with the amount of money you'd have in it, you could have put a significant down-payment on a NICE G8...

Not everyone wants a G8 Ed.

Just making a comparison. Or Silverado 1500, or Taurus SHO, or Dodge Charger.

Honestly if I were you take everybody's opinions on here.... Then do a lot more of your own research. Search a lot of Grand Prix forums. A lot more hardcore modding info on those sights. 400hp is not impossible, but will require some $$$ for sure

00Beast wrote:Just making a comparison. Or Silverado 1500, or Taurus SHO, or Dodge Charger.

I was just teasing. Honestly the key is research. But if you want bang for the buck, turbo.

400hp?

Turbo is the route you should be taking IMO as well

With 1.9 rockers on 93 octane people hit 350 wheel with a Cartuning turbo kit.

I think we all have thought about various performance mods, and I dont know of anyone who doesnt want the best of both worlds...power/drive-ability/decent economy. The 3800 in my GP and again in Bonne have been solid engines and I've read more threads than I can count about top-swaps/builds/blowers/turbos.
I have steered away from most all since DD use and hi-way cruise performance are high on my personal list, but I can easily say that in the past ten years I've seen/read about more turbo cars going the distance after a build. The stock L67/L32 are great engines but heavy mods make them self-destruct in lots of cases, and extreme turbo boost will do the same, but a mild turbo build can easily deliver a streetable 300whp with totally destroying the engine or fuel mileage.
Personally, I think 300whp is stout figure for a street car and capable of moving a Bonneville with real authority. I'd love to drop a LS4 in my car just for the torque and V8 exhaust note, but a good turbo 3800 will dust the LS4 and use less fuel doing it. I've even got a "L36 Turbo" decal design saved on my hard drive just in case!

Gosthawk, I thank you for your advise. Like you I admit that I read too many forums to mention. I have moved further away from this site since everyone wants to argue instead of help you, yet they know the right thing to do, but have no clue what they are talking about. The grand prix guys know what they are talking about since they mod their cars. I have decided to supercharge instead of turbo. I like the turbo idea, but my main objective is to get rid of the plastic plenum. If I can upgrade and supercharge that is my goal. Since it has been freezing, I haven't been able to start the mod yet. I am confident this will work out, and with a few extra mode during the project, it will make this car snort.

Bonnie01 wrote: but my main objective is to get rid of the plastic plenum.

You could get the aluminum plenum from a series III. I think there is only a couple changes to be made to make it work properly.

Last year the plenum failed and hydro locked the engine. I replaced the plenum, then I started to get misfire codes. I replaced all the plugs, wires, and coils. Still misfire codes. Someone commented that it was the head, so I had the heads worked on, and ported and polished. Still misfire codes. I gave up and took it to the dealer. They spent 3 weeks trying to figure out why the code kept coming on. They tore down the motor and found that the connecting rod was bent just enough in cylinder 2 that the piston w's coming to the top. So $1500 later the top of the motor was reworked and a connecting rod was replaced. Still have it. I'm worried that it will happen again in south Dakota weather, and would rather spend the money upgrading than fixing existing parts.

Also, my research has found that if I do the topswap I will get 5% more horsepower than the stock ssei. With ordering parts from Bonneville unlimited, the price makes it easy to do. Since I'm tearing the top off, I can replace some parts such as the valves and springs, replace with headers, valves, pushrod, a cam, and some minor mods to gain the horsepower where I want it to be. I have made a list, just waiting for spring to roll around and build a beer budget to entice the friends to help. I would like to use a dyno to test the gains after every mod, but the import guy in town is an ass and blew me off when I talked to him about Bonneville.

Not to scare you, but I think you should be aware. 3800s don't tend to hold up very well once you tear into the factory rotating assembly/bottom end. Especially under higher boost levels. Will something definitively happen to yours? Who knows. But I thought you should know. Mostly everyone suggests dropping in a used motor.

That aside, a topswap will make more power because the L36 pistons net a higher compression vs the L67. 9.4:1 vs 8.5:1. This means that you have to be a little more careful tuning. Without headers, you need to run a 4.0 or 4.2 pulley on the blower after the topswap. But with headers and good tuning a couple of the W-body guys have hit 13s on a stock 3.8 inch pulley.

Make sure you give everything a good cleaning before you install. Also some porting in the LIM, heads, and blower will help lower knock levels and the blower will whine louder.

I would advise you to find someone in your area who can tune 3800s, that'll make your life a lot easier. Plus in-car tunes are the best kind of tunes.

In regards to the L26 Aluminum plenum, I think all you need to put it on an L36 is the throttle body adapter from ZZP.

If I were closer, I'd love to come by and help you wrench! Best of luck with the swap. Take some videos when everything is done.

Thanks for the info Carl! I have been debating about pulley size. Ive been accumulating parts here and there to hide from the old lady till spring. Since my garage isn't heated, I'm waiting for warmer temps to get started. No sense in fighting freezing tools and frozen beer. I have a machine shop here that will inspect,soak and bead blast parts for cheap. Also I found an old hot fodder that has a great reputation with electronics and tuning. He's not cheap but so far he is the only one I can find.
The motor is in great condition. Have not had an issue with it. I'm doing this project now just to spite all the no Sayers. Besides their are jealous we can upgrade!

There are many naysayers out there, and a bunch on this forum as well. Some will argue and say sell the car and get an SSEi and others will just say it will blow up... bottom line is if it is what you want, do it. I am certainly excited to see some of the naysayers get put in their places over the whole top swap debate. Not at all to say that it is an easy mod with no risks associated with it, but proper planning and doing it right will yield good results and a setup that will last many miles.

I will say though that even though a Grand Prix has the same transmission, remember that they are also lighter and often will have lower gearing which combined will have a significant impact on the life of the transmission when throwing more power down it's throat. There have been a few broken stock input shafts here from modding on a stock trans, so do be careful of that.