EFI vs. Weber

[Gordy]

How would stock Opel 1975 fuel injection compare performance wise to a good Weber 32 36 on a redone 1.9 liter with 9;1 pistons, mild cam and maybe just upgrading the valves to 2.0 intakes and exhausts? It would be in a 1975 Manta so the efi hook up etc should not be a problem. How tempermental was the efi, because I've never had a 75 Manta before.
I picked up this Manta with 26,000 original miles, original paint (not perfect) and egads! original tires! The efi is in the trunk. The car was in heated storage for 30 years and they put a carb on it to get it to run...at all.

[Paul]

The FI on the 75 Manta is not temperamental at all. In the stock, unmolested form, its very stable and nice to drive.

There are 2 problems.... (1)isn't not adjustable and (2) the flap door style air flow sensor doesn't like cams with a lot of overlap. The excessive overlap will make the flap bounce and drive the computer nuts. However, I ran an Isky OR-66 cam for many years w/o any issues... coupled with flat top pistons. The FI can't handle the really good cams with 106 or 108 centerline... The lack of adjustability means the FI system soon runs out of abiltity to increase fuel in the upper RPMs.... usually starts to go lean above 4500.

The engine I built for my 75 Manta, I kept these issues in mind when selecting components like the cam. You can build a fairly strong engine, say 110-115HP, and still use the stock FI, but that's about the limit

[DennisGardiner]

I will add to the previous post. The 75 EFI is pretty bullet proof, as long as you keep the computer dry. {Ask me I'll tell you a tale of a friends car.}

I have run 1975 EFI on two cars; a retrofitted 74 Manta and a Kadett. The Manta was bone stock, ran perfect, but slightly less power than the 32/36 I had.

On the Kadett, I had 9:1 pistons, stock cam and the 75 EFI exhaust manifold. Ran great. Good power!

But the 75 EFI was designed by Opel to run on the lean side. This gave to good fuel economy, but as already stated, the system is not adjustable. So a cam is out of the question.

The other draw back to the 1.9L 75 EFI is the complicated throttle set up, that hooks the cable housing to the valve cover with the cable attaching to the rear of the center run throttle rod.
(in comparison the 2.0L system is cleaner as the throttle cable attaches directly to the throttle plate and manifold.)

If you want a cam.... use the simpler 2.0L systems manifold, throttle plate, t-stat, injectors, but not the computer. You would want to use a Lap-Top program-able system, such as from Redline.

[2 Fast 4 U]

Originally Posted by DennisGardiner I will add to the previous post. The 75 EFI is pretty bullet proof, as long as you keep the computer dry. {Ask me I'll tell you a tale of a friends car.}

just did

[Gary Sullivan]

I have had several carbed Opels as well as EFI's and my experience with the injection is that it is very solid, fabulous for economy and trouble free.
On the other hand, my first GT was a 69 and its Solex gave me fits. I am currently running both carbs and EFI on my cars and I was hugely tempted to convert my other GT over the the EFI.

Gary S.

[BobCGT]

Last winter I converted my GT over to EFI and Getrag 240 trans.
I have been very pleased with the way the car operates.
Previously had a Weber 32/36 carb,that worked well also.

[pvcar]

well ive been thinking about the EFI conversion on my gt, currently has 1.9 with sprint exhaust and a weber 32/36. my question is how well does it fit in the gt engine bay does it look clean once installed. also i read a few threads back that the opel EFI is not adjustable but you can op to use a programmable unit how does that work and whats the cost of a unit like that??
Specialist Juneau

[BobCGT]

The LE Jetronic system (2.0L) that OGTS sells, looks good in the engine bay in my opinion. The rear of the intake plenum is close to the cowl flange.
I moved the cold start injector from the rear of the plenum to the inboard side just to make a little room back there.Easier to get at also.