[69gt]

Thinking of putting a ford 9 inch in a gt with a 4.3 chev engine to power it and possibly a six speed trans. large undertaking I know but, gotta be different. Has anybody done either of these swaps and if so what are some of the suprises to look forward to. I saw the threads on the Toyota rear end and saw all the great ideas and comments and was wondering if possibly the 9 inch is too big and heavy. As for the engine there is lots around, and easy to come by extra parts and perfomance goodies. Any thoughts or suggestions welcomed. Thanks in advance

 

[RallyBob]

Well, as most everyone here knows already, I'm don't care much for engine swaps in Opels, BUUUUT (I digress!), if you're gonna swap in an engine that's making under 300 hp, the 9" Ford is pretty much overkill. It's also physically very large, and would either require cutting the floorpan up substantially to allow for suspension travel or jacking the rear of the car up a LOT. I think an 8" Ford or Toyota rear axle might be a better choice, lots of options out there for gearing and limited slips.

Watch out for that 6-speed tranny swap too, those suckers are physically very large, and would probably not fit in a GT tranny tunnel (I assume you mean either a T56 or ZF 6-speed?) So at this point, we're talking semi-tube frame and custom sheetmetal for the floorpan! You're possibly better off buying a kit-car chassis with a stronger suspension, bigger rear axle, and bigger brakes, then installing your driveline into it, and just dropping the remains of the GT body over the chassis. Otherwise you're going to have to reverse-engineer every part of the GT to fit the bigger rear end, bigger engine, bigger brakes, stronger front suspension, 6-speed tranny, rollcage (it will probably need it), improved cooling system, etc.

Just some food for thought, in my 11 years of running an Opel shop, I only saw 6 complete GT's with nicely done driveline swaps, and probably saw about 100 or more go to the crusher half-finished....

Bob

 

[Maddyn]

I've seen pictures of a V-8 GT before, but if you're going to do it right you'll basically have to build a tube frame for the car. The stock unibody won't handle the torque of a V-8, first time you stomp on it the car would probably twist into a pretzle (I would pay to see that )

But basically what you'd have to do is build some kind of tube frame, either just stiffen up the body, or build a full frame and affix the body to it. You'll most likely be redesigning the front suspension, both for the extra weight, and for a crossmember that will take the block.

Rear end wouldn't be too big of a deal, you'd probably want to make a 4 link system for something with that much power, so that means a little hacking of the rear floorpan and such.

A lot of your work will just be stiffening things up to handle the weight and power, and then some tight fitting in the engine compartment. Interested in seeing how it turns out, would love to know.

 

[oldopelguy]

one more view

Having owned a v-8 Vega and driven 2 v-8 Opels, I really think you would be happier with a new Ecotec 2.2L S-10 drivetrain or a Quad-four with Mantapart's tranny adapter. Both of these newer motors are easier to fit, lighter, and more fuel efficient. The new Ecotec is currently making 700 HP in a Cavalier that GM built on an almost stock bottom-end!

Get a good running 150-200 HP 4-cylinder into the car, either Opel or something else, and you will smile every time you drive it. Remember that at 175 HP yout HP/Weight ratio will be better than a 'vette, and you'll be able to drive past him at the pumps. If you really need to flog the car, get some NOS and blow-up the small motor a few times. You'll still be happier and save money. Why else do guys build Honda's?

As for the axle, the Ford 9" is way overkill in a car this small and light. All that unsprung weight would make the car handle poorly and you can't possibly get tires big enough to fit in the car and not break loose before the axle even breaks a sweat. A solid 7.5" GM or so will be plenty big, and parts are about the same price.

Best of luck, and keep us informed on what you decide to do.

 

[69gt]

thank you for the advice i was a little concerned on the rear end size, if using a toyota rear endis there much difference between a two wheel dive and a four wheel drive? the 4.3 is a v6 same as a small block chev only missing two cylinders. thanks again for the great advice will let you know what I decide.

 

[RallyBob]

There are a few variations of the Toyota rear axle. There's a 7.5" and 8" ring gear diameter, and also a 'high pinion' 8" from certain trucks. The big concern is the axles and gearing. 2wd trucks have a 5 x 4.5" bolt pattern (common, used on old Chryslers and Fords), while 4wd trucks have a 6 x 5.5" pattern , which is a truck-only pattern and limits wheels choices. Same overall width however. 4wd trucks also have a 4.10 axle ratio stock, while 2wd trucks varied a lot. 5-speed trucks with the 7.5" rear axle mostly had 3.73's, 4-speed trucks with the 8" axle had mostly 3.07's. then there were the V6 trucks (usually 3.23's or 3.42's), and the Turbo trucks (usually 3.42's AFAIK, with the 8" rear). But there are tons of options for rear axle ratios and limited slips, and the pricing is reasonable. Basically you can get anything from 3.07 to 5.71 and all in between for about $180, and limited slips are $280-$450 or so, depending on the brand.

Bob