Quote:
Originally Posted by opelgt73
I also have a GT that I am working on, currently it is in storage as I am overseas but I had just picked it up from the body/paint shop before I left
Here is my current plan,
For those of you that don't know the US model GT came in two engine sizes 1.9L and 1.1L. The 1.1L can regularly get 50-55mpg and the 1.9L was about half that. The 1.1L is significantly lighter, everything from the radiator to the motor to the brake rotors to the rear axle is smaller and lighter.
My goal is to break 65Mpg in mixed driving. There are several things I am going to modify that I believe will get me to that number. The first is the rear axle ratio. I am changing the 4.11 rear axle with a 3.89 (already have) from another model Opel, I have considered adapting a 5 speed manual (currently 4sp man) but I think the new rear end will give me the proper OD ratio. I am building a programmable FI system, the stock engine has two hard to adjust carburetors. I will also have a custom fabed exhaust system. I have not done a cost benefit of raising the compression but I may raise the compression. Beyond that the only engine modification I may experiment with is different cam ratios, but because I would have to have these custom made as there are none readily available, this is last on my list.
I also plan to do as much weight reduction as possible. Replace the metal hood and belly pan with fiberglass. Replace the steel wheels with light weight aluminum. Replace the steel radiator with modern aluminum. I don't know how heavy the stock seats are but I am guessing I can find lighter modern seats. Remove any unnessicary interior pieces.
So far I have I have a 71' 1.9L GT that I recent picked up from the painter.
I have a complete 1.1L drive train
taller gearing rear diff
A combined intake manifold that I can build a FI setup out of.
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I didn't know they made 1.1L GT , never say one .
On the gear ratios are you sure on that because I kind of remember the GT shared same rear gearing as standard Manta , which was 3.44 , the Manta ralley had 3.67 at least in the yrs of like 1970-1975 .
I always liked the 1.9L, its very strong engine with the way they engineered the head .
I later added a turbo to mine with upgraded 5 speed because stock 4 speed could not handle extra TQ (went through 3 trannies in one week an gave up on OEM one ).