My new car- 73 Opel GT

[jim-frank]

I'm restoring an opel gt, and plan to ecomod it in various ways. The first will be a short air dam at the front. The car has a fairly nice belly pan under the nose, so it remains to be seen if I'll put the dam at the very front, or after the nose pan. The Opels have a lot of under hood heat problems, so I'll be trying to vent the engine compartment behind the front wheels.

It has a 1.9 liter engine, with fairly low compression, and a carburetor. These factors are not the greatest for economy, but I have plans to use a vapor carb eventually. I have a ported and polished intake manifold, and a Weber carb that I can get jetted as lean as I want.

I'm going to build a performance engine for the car, with Somender Singh's grooved head design, higher compression ratio, lean burn carb, and exhaust gas temperature monitoring on each cylinder. That way, I can see just how lean a mixture can get without slagging my engine. I'll also have a cockpit adjustable ignition timing control, and I'm thinking that water or steam injection might also be of interest, as may hydrogen injection.

This car is for fun, rather than daily use, and using it as an eco test bed will be great fun.

Any ideas that anyone else thinks I should look into for this car? I want to have sporty performance available, with economy available too...

[EdKiefer]

I had a 1974 manta ralley with th 1.9L . that came with 7.5CR dished pistons and hydro lifters . rated at 75hp , there is the early 1.9L with 9.0 flat top with mech lifters which was rated at 90hp (I think was from 1970-71 ).
Those changes and I changed out to a weber progressive DD with a bit of rejeting and venturi size changes (stock carb was 24/28mm) and I ran 25/26mm .
This gave much better response from engine .

Ed

[Frank Lee]

I like them and was recently hunting on Craigslist for 'em- found a few good candidates too... looking forward to seeing what you come up with!

[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.

[EdKiefer]

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.

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 ).

[opelgt73]

Originally Posted by EdKiefer

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 ).

Yes the 1.1L is pretty rare, only 3500 were made out of 103,400 total GT's produced, and not all that were produced came to the US. I've only seen a few of them in the 15 years I've been into Opels. I've restored several 1.9L's. I had one I bored to 2.0L with a hotter cam and higher compression plus the Getrag 5-speed. It was a blast to drive, wish I hadn't of sold it!

Anyway I'm piecing together a 1.1L. And I will swap it into my current GT that is 1.9L. I managed to find a guy selling the entire drive train minus the radiator and complete set of carbs. Actually two complete drive trains. Although one is disassembled and the block is locked up.

About the rear end. The 1.1L has a completely different rear end/axle than the 1.9L Manta or GT. Everything about it is smaller and lighter. Except for the gear ratio it is the same rear end used in the 1.1L Kadett. The 1.1L GT had a 4.11 rear ratio and the Kadett had a 3.89 rear ratio. The reason being is that they wanted the GT to have more pep, being that it was a sports car and the Kadett was more of a standard compact. But if you use it in a GT it will essentially be like an OD ratio.

Luckily I managed to find and obtain both a 1.1L GT and a Kadett rear end. If you really want FE in your car I would suggest sourcing the 1.1L motor. While there weren't many GT's that came in the 1.1L trim there were plenty of Kadetts and Wagons that came with the 1.1L so they're still around and will bolt right into the GT.

By the way here is a list of differences between the 1.1L and 1.9L GT that help it reduce weight (that I can remember):

Smaller 1.1L Motor (You can literally pick up the long block and handle it by yourself, it's like a toy)
Smaller 4-speed transmission
Smaller diameter drive shaft
Thinner engine cross member
Smaller diameter rear axle (with different ratios)
Smaller front brake rotors and calipers
Smaller rear drums
Half Sized Radiator
Dual down draft carb so it has a different
Dual intake air filter snorkel (for the carbs)
Front Suspension leaf spring had 2 layers vs 3

I actually haven't sourced the front leaf spring yet. It serves two purposes, it is lighter and it allows the front end to sit at the proper height. Because the engine is so much lighter in the 1.1L if you were to use the 1.9L front leaf spring the front end would sit up a few inches higher.

In addition to the fiberglass belly pan and hood available you could use the earlier crashbar-less doors to save some weight too, but I think I'm going to go with safety......

[opelgt73]

By the way. The 1.1L motor is known to be bullet proof. Don't be scared away by it's relative rarity, Opel GT Source still sells all the parts you need to maintain it anyway.

Another cool Opel I've almost picked up before was the 1.1L Kadett Wagon. Pretty funky looking little cars with plenty of room and I know a guy who routinely got above 50MPG with his.

[jim-frank]

The 1.1 would be a great ecomotor, to be certain. I like your plan, it sounds pretty comprehensive. I've toyed with the idea of FI, but it sounds like a major PITA to get all the sensors, computer, and components set up. If I did go FI, I'd probably swipe the injection out of a Nissan Sentra 1.6 liter. (Since I've owned a couple, and know how they work)

I guess I need to search here and see how I can get a fuel flow meter that will interface to my Mpguino, and measure the fuel into the Weber carb. I sure love having real time mpg data...

[opelgt73]

I'm sure you know but there is a FI intake manifold that bolts right up to the 1.9L motor. The 75' manta had the same 1.9L motor and came stock with Bosch Fuel Injection. With a programable fuel injection computer you could really tweak the 1.9L for better mileage.

[jim-frank]

I'd heard about that FI system, but the odds of finding one at a reasonable price are sort of iffy...