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Please don't fall into the trap that almost every newbie Opeler falls into and get all caught up in trying to get the most gnarly engine possible in your ride. There's a lot more to a car than engine, engine, engine. Judging by your avatar photo, you've got a LOOOOOONG way to go before you can contemplate racing Hellcats on the highway. The next newbie trap is wheels. Every newbie spends enormous amount of time and money on $2000 wheels, while the rest of their car is a rolling schitt bucket.

sta cars on the road. The 2.e all set up.

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If you’re looking at the kegwasher project, have no fear. I’m not interested in cramming a finicky high horsepower engine into a GT. A lightly tuned stock engine will do the trick for me.
The wheels that I love are the old Cragar SS style but I guess those are loooong out of production. They look perfect to me.
 

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Pedal Smasher
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Sequential mechanical secondary. <img src="http://www.opelgt.com/forums/images/smilies/yup.gif" border="0" alt="" title="Yup" class="inlineimg" />

Harold
Ah, yes. My brain was thinking typical secondary carbs.
 

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Pedal Smasher
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If you’re looking at the kegwasher project, have no fear. I’m not interested in cramming a finicky high horsepower engine into a GT. A lightly tuned stock engine will do the trick for me.
The wheels that I love are the old crater SS style but I guess those are loooong out of production. They look perfect to me.
The only difference between a 1.9 and a 2.0, is the bore. The stroke is the same. The biggest problem with the 1.9S in America, the pistons have a big dish in them to lower compression on I want to say 1971-1973 engines. A set of pistons designed for the 1.9S, can really bump up the compression. That will wake up any engine. The 1.9S has a 93mm bore and you can go as high as 97mm on the CIH. Let’s say you went 96mm, with the 69.8mm stroke that would give a displacement of 2.02 Liters. That stroke is pretty short, so it would be rev happy.

Wossner and Wiseco both make pistons for the CIH, with Wiseco being noticeably easier on the wallet. But you have to really check all the math if you go with a high compression domed piston. Wiseco makes a flat top and that’s what I’m gonna go with for my 2.4 build. I could go with a domed piston but then I’d need a different cam to lower a 12:1 static CR.
 

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Just Some Dude in Jersey
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The wheels that I love are the old Cragar SS style but I guess those are loooong out of production. They look perfect to me.
I've seen quite few Cragar rims for Opels offered for sale over the years. You might consider placing a want ad on the Ad board for 4x100mm Cragars. You might be able to get a set cheap. Opels Unlimited might have some also.

:veryhappy
 

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Pedal Smasher
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While they cost a small fortune, I’ve always been a fan of the ATS Classic. I also like drag rims, that have been shaped holes in them but those are kinda hard to find.

 

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While they cost a small fortune, I’ve always been a fan of the ATS Classic. I also like drag rims, that have been shaped holes in them but those are kinda hard to find.


Those do look pretty sharp. I would like something that has the 70’s look to them. I think the GT would look wrong with rubber bands wrapped around oversized rims. Ultra low profile tires don’t ride that nice at any rate.
With any luck I’ll be thinking of wheels and tires by next spring.
Nice German plate on that GT BTW.
 

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The only difference between a 1.9 and a 2.0, is the bore. The stroke is the same. The biggest problem with the 1.9S in America, the pistons have a big dish in them to lower compression on I want to say 1971-1973 engines. A set of pistons designed for the 1.9S, can really bump up the compression.
That sounds pretty good. What is the expectation for an engine with the better CR and all other hardware stock? How much do you get with the flow improvements? From what, about 90 HP factory to 110HP or so? Increase the grin factor by a good 20% ?
 

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Pedal Smasher
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Well some broad generalizaties... you should produce around 90 to 100 fwhp per liter of displacement, naturally aspirated but this is also more of a modern figure. Not all engines do, if intentionally handicapped or plaqued by bad designs and some engines do better than that. The CIH would be an engine that comes in below the norm, it doesn’t produce power very well compared to say a 426 Hemi. And it’s something like 5 - 10% increase per point increase in static CR. Porting and polishing can be all over the place. Good cylinder head work can really increase the volumetric efficiency of an engine, but if a person just goes in there and digs out the ports, the engine will lose power. Porting is both a science and an art form, and I’d say anyone who specializes in cylinder heads would say they’re artists.

Engines are definitely a whole picture deal. If you improved every aspect of an engine by just 1%, the net gain would be significant. The CIH is a very crudely designed engine, focused on being economical. The forum could give you all kinds of advice on how the improve a 1.9S, but without knowing how much you want to spend and how much you believe you can do yourself, that might not be helpful.
 

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but without knowing how much you want to spend and how much you believe you can do yourself, that might not be helpful.
When it comes to doing it myself I’m a former aircraft mechanic and engineer. I know my limits and will gladly go to experts for things like porting and balancing. I have a good set of tools but don’t have any special tools for honing of cylinder walls or such.
I’ve seen people posting about fabricating exhaust and intake manifolds but that sounds like something best left to the experts.
As long as this car is almost completely disassembled I am willing to complete the tear down and repair/replace all parts affected by aging.
I’m not rich by any means but I don’t mind spending what it takes to get the car back together and running well as well as reliably.
When it comes to the engine I’d love to do what I can but let the experts help in rebuilding carbs and porting. I can follow directions and wrench but am not an artist or expert. I can follow advice and usually know when to seek it out. My vision is for a peppy but reliable engine. I don’t need the most hp available. I’m old enough to prefer cruising to tearing down the strip. Lol
 

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Pedal Smasher
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You're a former aircraft mechanic and an engineer. Don't sell yourself short, I bet you could learn how to do pretty much anything on a GT. My background is engineering, and I plan to do everything except the needed machining on the engine. The only reason why I'm not doing that, I don't have the crazy expensive machinery needed to do that. I plan to even do the porting and polishing work, I know enough to do a cylinder head for myself. It's more about smoothing transitions out than anything else, and as long as I stick to that I should be able to port and polish a stock head just fine. I'm even going to handle the paint job myself. The biggest thing in restoring a car is time, take your time and be patient. It's therapeutic for a reason.

I also have a fear of letting anyone else work on whichever GT I end up buying, so I might as well learn how to do it all. That will also save me tons of money, both in not paying a therapist and not paying for labor. I'm currently a math teacher, so this will become my long term therapy for sure. As far as vehicles go, a GT is very basic in how things work. Even for the era, the GT is pretty simple.
 

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I plan to even do the porting and polishing work, I know enough to do a cylinder head for myself. It's more about smoothing transitions out than anything else, and as long as I stick to that I should be able to port and polish a stock head just fine.
There's no reason a person can't port their own cylinder head, except for the fact that you shouldn't bother if the head is stock!

Stock sized valves in a 1.9 head are very inadequate. I've flow tested many heads ported by other people, including race shops. Every single ported 1.9 head I've flow tested except for ONE, flowed worse than stock. Even there, the one head that flowed better (done by a professional Opel race shop in the 1980's) than stock only gained 1 cfm on the intake ports and three cfm on the exhaust ports.

Certainly not worth pulling out the die grinder for that! Not only was it a lot of work, it made the intake/ exhaust proportion worse.

Unless you are installing bigger valves I always recommend just leaving it alone. You can definitely make it worse than stock otherwise!
 

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I plan to even do the porting and polishing work, I know enough to do a cylinder head for myself. It's more about smoothing transitions out than anything else, and as long as I stick to that I should be able to port and polish a stock head just fine.
There's no reason a person can't port their own cylinder head, except for the fact that you shouldn't bother if the head is stock!

Stock sized valves in a 1.9 head are very inadequate. I've flow tested many heads ported by other people, including race shops. Every single ported 1.9 head I've flow tested except for ONE, flowed worse than stock. Even there, the one head that flowed better (done by a professional Opel race shop in the 1980's) than stock only gained 1 cfm on the intake ports and three cfm on the exhaust ports.

Certainly not worth pulling out the die grinder for that! Not only was it a lot of work, it made the intake/ exhaust proportion worse.

Unless you are installing bigger valves I always recommend just leaving it alone. You can definitely make it worse than stock otherwise!
the engines I have were sitting out under a tent for 25 yrs without running. I’m going to pick the best one for rebuild/ restoration. I was thinking of pulling the head and getting the Valve seats and guides redone for unleaded fuel but that’s about it. I’ve Seen in the rebuild threads that porting the heads is best left for the people putting in bigger valves and wilder cams. I haven’t seen any threads where a different cam was recommended for a daily driver grin generation machine.
Manifolds and carb are also open points for me. Dual carbs sounds fun but I remember the joys of synchronizing them on motorbikes and will pass. A nice peppy Weber or such looks like the only option if FI doesn’t fit (rats!).
 

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Bob, I have a 2.4 coming this Friday and that’s the engine I’ll be modifying.

Some GT owners have done fuel injection on a CIH. There are a few ways to go about doing that. If that’s what you want to do, are you wanting to use Opel parts or go for the custom route? The CIH was used for like 40 years, so there are Opel solutions.
 

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Bob, I have a 2.4 coming this Friday and that’s the engine I’ll be modifying.

Some GT owners have done fuel injection on a CIH. There are a few ways to go about doing that. If that’s what you want to do, are you wanting to use Opel parts or go for the custom route? The CIH was used for like 40 years, so there are Opel solutions.
2.4 is a little bit different. However it exhibits the same high exhaust flow ratio of a 1.9 head. Just more of both. It flows 110 cfm intake/93 cfm exhaust.

I'd limit the work to the bowls then. No reason enlarging the ports on most street applications unless going to bigger valves and healthy cam.

Stock Opel 2.4 EFI (Motronic) is arguably the best used on any CIH engine. But there are two distinct issues. You still have to be careful if changing cam specs...low overlap only! The heads do like high lift, and wide LSA works well on bigger CIH engines.

The bigger issue is that the OEM EFI 2.4 intake in no way fits under a GT hood. Even the cut down 3.0 liter 6-cylinder intakes are a tight fit, and while they flow better than a 1.9 intake, you are leaving a lot on the table. I've flow tested a 2.4 head with cut down 3.0 intake and it choked it down a lot compared to modest 45 DCOE's with 36 mm venturis. There's a reason all the rally guys use 48 or 50 DCOE carbs on 2.4's....they need it!
 

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Bob, what is the best intake and exhaust valve size in your opinion for the 2.4 head? I’ll be just below 2.5L.
 

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Bob, what is the best intake and exhaust valve size in your opinion for the 2.4 head? I’ll be just below 2.5L.
Well, there is no 'best' size. There's a best for your application.

Camshaft choice
Degree of porting
Final bore size
Induction
Exhaust

And then there's budget. 11/32" off the shelf Chevy valves are cheap and work well. But nobody is using those in racing engines, they are more likely using 7 mm custom made racing valves. Big price differential, but if you run an aggressive cam and/or run high rpms, the lighter valves and associated valvetrain pay huge dividends. Less valvetrain wear, higher airflow, more rpms, lower spring rates, etc.

These components are the difference between a 180 hp engine and 220-270 hp.
 

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Hi RallyBob, do you know why is the stock EFI such an under performer? I’d always heard a carburetor might have a higher peak horsepower but for power over a wide band fuel injection would be best.

Any thoughts on the worth of four engines stored under a tent for about 25 years? I’m assuming a complete tear down will be needed as a minimum. Will they have rusted up beyond all holes?
BTW; i got four as the deal was all or nothing. Every Opel part he finds laying around whether I need it or not.
 

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Hi RallyBob, do you know why is the stock EFI such an under performer? I’d always heard a carburetor might have a higher peak horsepower but for power over a wide band fuel injection would be best.
Because L or LE Jetronic uses a flap-type air flow meter and cannot tolerate much in the way of modifications.
 

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Opeler
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2.4 is a little bit different. However it exhibits the same high exhaust flow ratio of a 1.9 head. Just more of both. It flows 110 cfm intake/93 cfm exhaust.

I'd limit the work to the bowls then. No reason enlarging the ports on most street applications unless going to bigger valves and healthy cam.

Stock Opel 2.4 EFI (Motronic) is arguably the best used on any CIH engine. But there are two distinct issues. You still have to be careful if changing cam specs...low overlap only! The heads do like high lift, and wide LSA works well on bigger CIH engines.

The bigger issue is that the OEM EFI 2.4 intake in no way fits under a GT hood. Even the cut down 3.0 liter 6-cylinder intakes are a tight fit, and while they flow better than a 1.9 intake, you are leaving a lot on the table. I've flow tested a 2.4 head with cut down 3.0 intake and it choked it down a lot compared to modest 45 DCOE's with 36 mm venturis. There's a reason all the rally guys use 48 or 50 DCOE carbs on 2.4's....they need it!
Bob,

How would your modified 1.9 intake (the racing one you wrote on article about years ago) with the wedge under the bowl and all cleaned up work on a 2.4 head/2.5 engine setup. I was considering using the new Holley Sniper EFI carb setup which claims to flow enough for 350 hp. It is all self tuning and looks like a really nice deal.
 
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