Pro Touring GN ideas - its long, sorry

[84TXGN]

I have an idea for my car and I just want a few second opinions. I lurk and read here a lot, which has helped me get ideas for my car. Long story short, I have a Grand National that I've had since I was 15. It has seen good days and bad days and was my daily driver up until a few years ago. I was rearended last year and the frame was damaged so I took it as an opportunity to do the frame-off restoration/mods that I've always wanted. Its no longer my daily driver but it's my only "fun" car so I want it to do everything.

My goals for the car are to be a street car that is at home on a road course, autocross course, and the drag strip. I want to the car to look low and aggressive. I want to do as much of the work myself as possible. I love making something or repairing something and the feeling of accomplishment. I also can't afford to pay someone to do everything I want. I also want to be a little different while keeping the soul of the Grand National intact.

Frame: My ideas so far are to box and strengthen a spare GN frame that I've obtained. I can weld a bit so I'll take on this myself or at least as much as I can. I'm fairly confident I can handle this or can at least learn what I need to know.

Front Suspension: I'll go with SPC upper/lower a-arms and AFX spindles for the front. I have all new steering linkage as well. I like the new speedtech coilover mounts that weld to the frame so I'm leaning towards those and a set of viking adjustable coilovers.

Rear Suspension: Here is where things get interesting. I want the car low and while there are bolt-on products that help with bind issues, the 4-link on the G-body isn't the best. My idea is to get a 4th gen f-body 12 bolt or 9" with g-body lower control arm mounts. I get to keep part of it using stock replacement stuff and eliminate the main problem, the upper control arms. I'll fab a crossmember for the torque arm and run a fays2 watts link. That will give me a better set-up for my jack-of-all-trades goals and let me lower the car quite a bit. Plus I don't think its been done before or at least isn't common. If I'm having the 12 bolt rear end built I've thought about having big ford axle tube ends welded on to elimate c-clips and allow more brake options. I think UMi's rear coilover kit with Viking shocks will go well here.

Engine: I'll keep my GN v-6. I have a heavily modified and strengthened engine that's capable of 600 hp at the wheels. Plus a GN has to have a v-6. I do want to look at using buick performance parts to convert it to dry sump for road course reliability.



Transmission: I think I want to keep an automatic in it but I'm not sure. Right now my first option is a 6L80E conversion using the PCS controller from Zero Gravity and a paddle shifter. It'll take a little fab work and some custom parts but I like the idea. I want to experience a well tuned 6L80E to see if it will give me the feel I want before I go this route. My back-up plan is to go with a T56. This swap was just recently completed and uses parts that are readily available. I'm just not sure how the GN engine will act with a manual behind it but its probably something I can tune around. The timely release of an aftermarket 8L90E controller would be great too but I'm not holding my breathe.

Interior: It'll be mostly stock with good track-ready seats. I'd love a 5 point harness but I haven't figure out how to mount it yet. A harness bar is a possibility, but I haven't totally ruled out a roll bar/cage. A roll bar is much more likely. I never use the back seat and don't know if I would when this build is done so part of my says just put in a roll bar. Another part of me isn't sure about a roll bar because I'd be picky with fit/finish and squeaks. In the end I know a roll bar makes sense and can be removed but for some reason I have a hard time committing to it.

Exterior: BLACK. It has to be black. Its a GN. However, I want to add GNX fender vents, functional to remove engine heat, and GNX fender flares. I'll use a fiberglass hood and deck lid to reduce weight. I'd like to add a front splitter and slightly more aggressive read spoiler as well. I love the look of 18" CCW classics on GNs but they have been done. My thought was to run them with copper centers, which I don't think anyone has. I haven't seen them on and GN but copper wheels on black cars is a good look, to me. I have a set of trans am wheels that look similar that I will paint the centers copper to see if the look is something I like.


That's pretty much it. I'd love some feedback and advise. This will be a long project so things may change down the road but I'd like to have a good idea of what everything will look like. I'm not afraid to learn new skills. My dad is a mechanic and I've been in the garage for almost 20 years building engines and race cars. My friends and I built a Lemons Fiero that we can't seem to keep on track but that's more about it being a Fiero than our abilities. This will be more fab work that I'm used to but nothing seems to difficult. Thoughts? Opinions? Cautions?

Thanks for reading.

[TonyHuntimer]

84TXGN,

I don't really have anything to add, other than I love G-Bodies! Good luck with your project.

Do you have any pictures of your car in its current state?

Regards,
Tony Huntimer

[NJSPEEDER]

Sounds like a fun project. Big thing is matching up the budget to the goals. If you have the scratch for something like a Schwartz chassis you would gain a ton of additional chassis stiffness and all the handling that comes with it. It would be a lot more performance than you will be abe to get out of the stock chassis.

Transmission, I love manuals. Since g-bodies did come with 4 speeds all of the linkage exists to put a stout 6 speed behind that turbo motor and have fantastic highway cruising. It could be the fun car and the road trip car at the same time. Built overdrive auto vs 6spd conversion isnt much of a price difference once you add up all the parts so food for thought.

Good luck with the build

[carguykeith]

Sounds like a pretty well thought out build to me, I do have a couple of comments though.

I've read a couple of build threads with manual convertions with the turbo 6 that didn't have super happy campers at the end. Having to loose all of the boost to shift and then building it back up was the big complaint. The turbo LS guys don't have that issue since they have the cubes to carry over but not so much with the 3.8... If you have the coin the 6l80 would be nice but a paddle shifted 4l80 would be half the cost and I bet just as fast.

Have you thought about going with a full floater rearend, best way to get rid of c-clips and have zero pad knock back bar none. Your idea with the 9" big bearing ends will work too, just make sure you use a floating caliper style rear disk setup.

As for the rollbar, yes, yes, yes and yes. These g-body frames are wet noodles and even boxing and bracing wont come close to the rigidity of a 6 point rollbar. Also if you plan on drag racing its a must have anyways, at 600 WHP you're definitely going to break 11.5's...

Just my $.02

[Interceptor5588]

Second the motion on the 4L80, no need for a fancy automatic. Turbo V6 has plently of midrange and doesn't need to be constantly shifting to keep it in its powerband. Manual -- I've always thought that the turbo/auto was the perfect combo. Turbo V6 with a stick would be a handful on the roadcourse, trying to predict when the boost comes back on and then try to manage those 600 horses as they come out of the corners. Make sure you have PLENTY of engine cooling, turbo auto will make lots of heat on full boil at the track.

I'm not sure the stock 109 block is up to roadrace duty, never went there with mine. I would suggest you speak to Messrs Duttweiler or Hartline.

[84TXGN]

Sounds like a fun project. Big thing is matching up the budget to the goals. If you have the scratch for something like a Schwartz chassis you would gain a ton of additional chassis stiffness and all the handling that comes with it. It would be a lot more performance than you will be abe to get out of the stock chassis.

Transmission, I love manuals. Since g-bodies did come with 4 speeds all of the linkage exists to put a stout 6 speed behind that turbo motor and have fantastic highway cruising. It could be the fun car and the road trip car at the same time. Built overdrive auto vs 6spd conversion isnt much of a price difference once you add up all the parts so food for thought.

Good luck with the build

I think the Schwartz chassis is nice but a little out of my budget. Its $10k for just the basic chassis and that's before you add all the other stuff. I think I can get a stock frame to be just as rigid but it'll weigh more. Plus I get the fun of building it myself

Sounds like a pretty well thought out build to me, I do have a couple of comments though.

I've read a couple of build threads with manual convertions with the turbo 6 that didn't have super happy campers at the end. Having to loose all of the boost to shift and then building it back up was the big complaint. The turbo LS guys don't have that issue since they have the cubes to carry over but not so much with the 3.8... If you have the coin the 6l80 would be nice but a paddle shifted 4l80 would be half the cost and I bet just as fast.

Have you thought about going with a full floater rearend, best way to get rid of c-clips and have zero pad knock back bar none. Your idea with the 9" big bearing ends will work too, just make sure you use a floating caliper style rear disk setup.

As for the rollbar, yes, yes, yes and yes. These g-body frames are wet noodles and even boxing and bracing wont come close to the rigidity of a 6 point rollbar. Also if you plan on drag racing its a must have anyways, at 600 WHP you're definitely going to break 11.5's...

Just my $.02

I've read several threads on the Buick forum of t-5 swaps and they have mixed results. The one guy I know of that has a t-56 behind a buick v-6 hasn't run it yet and it more focused on drag racing. Supra guys get their car to work fine and there are other examples of low displacement turbo cars that have manual transmissions. I figure there has to be a way to make it work but it might take me a while to figure out the right tune and turbo combination. It would make cooling a lot easier.

I know a roll bar makes sense, I just have to get over my anxiety. My only real concern is noise/vibration through the tubing.

Second the motion on the 4L80, no need for a fancy automatic. Turbo V6 has plently of midrange and doesn't need to be constantly shifting to keep it in its powerband. Manual -- I've always thought that the turbo/auto was the perfect combo. Turbo V6 with a stick would be a handful on the roadcourse, trying to predict when the boost comes back on and then try to manage those 600 horses as they come out of the corners. Make sure you have PLENTY of engine cooling, turbo auto will make lots of heat on full boil at the track.

I'm not sure the stock 109 block is up to roadrace duty, never went there with mine. I would suggest you speak to Messrs Duttweiler or Hartline.

I know a 4L80 is a solid platform but that's a lot of work for just paddle shifters. My 200-4R is fully built and can handle whatever I throw at it. The idea of the 6L80 is to add that little bit extra. Plus again it'll be unique. The transmission is the one item that I really just don't know what I want yet. I'm really considering the 4L80 though.

My 109 block has billet mains and a girdle. The only thing I worry about is heat and oil. I will run the best radiator I can find with an external oil cooler to help. I also want to convert it to dry sump. I can make a pan or have one made. The off center stage II front cover will bolt right on and is set-up for a dry sump oil system. They make all of the other pieces I would need. I could just baffle the pan and run a accu-sump but I feel like that's a waste of time and money when a dry sump is doable and will be 100% better.

I really appreciate all of the input so far. Keep it coming.

[jdsfastgn]

Just wanted to give you a bump because this could be the best Buick Build in Houston by far. Looking forward to getting started on it.