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Discussion Starter · #1 ·
Hello all, I have a completely rust free 1970 GT that I'm in the process of restoring. The body is just as stiff as when it left the factory, no rust to speak of whatsoever. I would like to build my engine up to the 160-170 horsepower range and I am curious if I would need to stiffen the body anywhere to keep it straight. I would like to know if anyone knows of any areas of the body are prone to warping when more power is added. I'm not worried about keeping it stock as I plan to do many modifications, both mechanical and cosmetic. Thanks a bunch.
Attached is a pic of the car at the present moment, just a bit more sandblasting before I rustproof the entire undercarriage.
 

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I don't know if you'd need any stiffening, as what you're shooting for has already been done by several members with anything from the 1.9 to the 2.4, or V6's straight 6's and V8's. The GT body is a strong little unit, and unless you plan to make it a Targa or convertible, it's handle most anything. Interesting frame to hold the body there....
 

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Discussion Starter · #3 ·
Thanks Gene, I just wanted to make sure seeing as I am now in the stage to do any such mods. The frame is just something I whipped together at the end of last summer so i could move the shell around easier. It just mounts to the GT's stock suspension locations and is extremely solid.
 

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Ben;
Could you do us a favor? We have some who are about to start, or have started their restos, and your idea for a frame is just one of many, but, can still give future restorers some ideas. We have had some made of wood, modified two engine stands, to bungee chords from rafters (yes, it's true), but, this may help someone in the future, so, post some pictures in the thread (use the search feature) and help someone. Still, a nice job.
 

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IMHO, if you have the chance to seam-weld the unibody it CAN'T hurt. From the factory, the body and "frame" (which is really just heavier sheet metal formed and welded to to the sheet metal) is held together by a number of spot welds. That works well enough for a mass-produced car but still can't be as effective a seam welded body. I believe it is standard practice to seam weld pretty much any unibody car body used in racing or rallying, mainly to minimize body flex that would otherwise translate into undesired suspension movement. As an example of what is easily done when a GT is sandblasted and on a rotisserie, have a look at my GT restoration photos with the seam welding starting at
Seam Welding 2008 - Opel Photo Gallery

HTH
 

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Ben;
Could you do us a favor? We have some who are about to start, or have started their restos, and your idea for a frame is just one of many, but, can still give future restorers some ideas. We have had some made of wood, modified two engine stands, to bungee chords from rafters (yes, it's true), but, this may help someone in the future, so, post some pictures in the thread (use the search feature) and help someone. Still, a nice job.
Yes, please post the specs of that frame! My 14 year old daughter wants me to build her a GT but I only have 2 years to do it. :banghead: This would speed up the process dramatically.
 

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What a interesting design of rotisserie.:yup: I went the Kwilford way but to each their own. Your also VERY lucky to have a rust free GT..I have at least 120 hours of steel work to do on my GT.:banghead:
 

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... I would like to build my engine up to the 160-170 horsepower range and I am curious if I would need to stiffen the body anywhere to keep it straight...
Interesting Ben
As I'm sure that you already know about stress fractures. It's more important than keeping the body straight. The fox body flexes and hooks the rear tires sooo good that even the chevy guys(outlaw) runs the chassis. A little flex can be a good thing.

The 160-170 is a high goal not that I'm saying it can't be done mind you.
How are you envisioning the driveline and power plant is what I'm asking.
 

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Discussion Starter · #9 ·
What a interesting design of rotisserie.:yup: I went the Kwilford way but to each their own. Your also VERY lucky to have a rust free GT..I have at least 120 hours of steel work to do on my GT.:banghead:
Thanks, It was originally a California car and spent a lot of its life in Nevada (where it was last registered with GIMAQT plates :)) I picked it up off ebay from a guy in Michigan. For the nice solid body there were some imperfections though, the interior was nasty and most of the rubber will need to be replaced, I found a rusty GT that spent its whole life in Michigan though with fabulous interior, even a perfect dash.
Good luck with your bodywork too, I hope all goes well and you can finally get it on the road and enjoy all the hard work you put in.
 

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Discussion Starter · #10 ·
The 160-170 is a high goal not that I'm saying it can't be done mind you.
How are you envisioning the driveline and power plant is what I'm asking.
I'm planning on using an Opel engine, I will probably bore out my 1.9l to 2.0l and get a 2.0l head with the bigger valves. I may have to get a 2.2l or 2.4l crank for some more torque. I'll most likely do some porting and polishing of the head. I haven't decided on fuel injection or tuning up my Weber carb yet. I'll run a custom aluminum radiator with electric fans and cancel out the belt-driven fan. For a transmission I'll mount up the 5-speed Getrag with a beefier clutch.
Is my goal of 160-170 feasible with that set-up, or what should I expect with that?
Thanks.
 

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Discussion Starter · #11 ·
IMHO, if you have the chance to seam-weld the unibody it CAN'T hurt. From the factory, the body and "frame" (which is really just heavier sheet metal formed and welded to to the sheet metal) is held together by a number of spot welds. That works well enough for a mass-produced car but still can't be as effective a seam welded body. I believe it is standard practice to seam weld pretty much any unibody car body used in racing or rallying, mainly to minimize body flex that would otherwise translate into undesired suspension movement. As an example of what is easily done when a GT is sandblasted and on a rotisserie, have a look at my GT restoration photos with the seam welding starting at
Seam Welding 2008 - Opel Photo Gallery

HTH
Kwilford, I was toying with the idea of seam welding the underbody, at least in certain areas for rust protection, but it is a good idea to seam weld more than I first thought for added support. Nice job on your seam welds btw, looking good.
 

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My 14 year old daughter wants me to build her a GT but I only have 2 years to do it.

By the way Chris, I think your daughter mentioned purple was her color choice. Check out the new Honda's on the lot. They have a wicked deep purple!
 

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I will probably bore out my 1.9l to 2.0l and get a 2.0l head with the bigger valves. I may have to get a 2.2l or 2.4l crank for some more torque. I'll most likely do some porting and polishing of the head. I haven't decided on fuel injection or tuning up my Weber carb yet. Is my goal of 160-170 feasible with that set-up, or what should I expect with that?
I'd expect a 2.0 block with a 2.0 head (stock cam) and EFI to make maybe 110 hp at the flywheel, no more. Even with mild porting, I would not expect much unless even larger valves and a more aggressive cam were fitted.

For comparison:

US-spec low comp. 1.9: rated at 75 hp, about 60-65 hp @ flywheel.
US-spec high comp. 1.9 (and Euro-spec 1.9): rated at 90 ps / 88 hp net (102 SAE gross hp), about 80-82 hp @ flywheel
2.0E: 110 ps / 108 hp @ flywheel
2.2E: 115 ps / 113 hp @ flywheel
2.4E: 128 ps / 125 hp @ flywheel

So while 160-170 hp is very achievable with a 1.9 or 2.0, it is not feasible for a streetable daily driver (unless forced induction is added), or unless you simply don't mind driving a race-spec engine. A 2.2 can achieve those numbers, but again the normal driveability will be compromised. A 2.4 can make those numbers fairly easily, but it won't be cheap and again, it won't be a 'smooth' daily driver.

I wouldn't let this deter you, there are a number of members here with 'only' 125-150 hp and I think most will attest an Opel moves along nicely with this much power compared to 60-65 hp.

HTH,
Bob
 

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No kidding...a stock 2.4 in a GT can turn it into a death trap, especially if you keep the stock suspension and brakes. I was shocked at the difference.
 

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I wouldn't let this deter you, there are a number of members here with 'only' 125-150 hp and I think most will attest an Opel moves along nicely with this much power compared to 60-65 hp
I totally agree, a lot of people tend to forget how light a GT is compared to most other cars, it only weighs in at some 2050 lbs, a late model Honda Civic can weigh 3-400 lbs more than that, so it doesn't take a whole lot of HP to make it go .... fast, slippery body shape too
 
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