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What / Which 6 cylinder CIH engine will mate with the getrag 5 / 6 speed trans and drop and fit into the Opel GT?

I blew the rings out of my 2.0 Opel engine and 4 speed racing autocross and need to upgrade / repair it. Definitely need a 5 speed trans for sure.

I'm looking at the Miata engine and 5 speed swap but so far I haven't found one that is completed so a little hesitant.

Thanks,
Dick
The 6cyl CIH's have a front sump oil pan which will interfere with the cross member. I fabbed a rear sump pan for my 24 valve 6 cyl, '72 wagon using 2, 4 cyl pans. I later redid it using a SBC racing pan and Opel pieces.
 

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Dick, you can put a straight 6 CIH into a GT but you'll have to relocate the radiator. Someone on FB just did this. The engine sits in the same spot, so no room for the radiator. If you really want 6 cylinders, I'd say you'll need to drop a V6 in. We have some members who have done this. It takes a lot of work though.

I don’t understand why relocating the radiator is a worse option than the V6. It would seem that there isn’t enough space on either side for the exhaust or accessories and up top not much room for the intake. Is the V6 that much lighter to make it a better choice? Short of putting a hundred kilo of ballast behind the seats the GT is going to be nose heavy. She’s got nothing in the a$$ to offset what’s upfront. Lol.
 

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Just Some Dude in Jersey
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What about a spiced up 2.4/5 at around 170hp and 200+ft/lbs of torque? That's about what you would get with a mild six banger, isn't it?

Do you need to rev really high during autocross like, say, 6000rpm, or are you more in the 3000-5000 range? Maybe a lower reving/higher torque stroker engine will work for you?

With a 2.4 almost everything in your car can stay the same.

If you go too big with the power you'll probably have to replace the whole drive train to handle it.

I would think that there are a bunch of turbo Jap engines and gear boxes that might fit.
 

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Although building cars is more about fun and personal taste than sense, my opinion is that a sports car like a GT should be as light as possible and with a good weight distribution so it can be driven fast through turns. And with a torquey engine that likes to rev. A six weighing 200kg up front seems like unnecessary understeer to me. It can always be mounted further back, but that means a lot of work with the firewall and transmission tunnel. A 122hp and 175Nm 20SE OHC engine weighing almost 30kg less than a 4 cylinder CIH would be my choice rather than a six.
 

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Pedal Smasher
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People have pulled off V6’s in the GT. Relocating the radiator is more of a problem because you don’t have a lot of room past the radiator to figure something out.

Personally, I say stick with a 4 cylinder CIH. I’ve got a 2.4 to work with, will wind up as a 2.5 or 2.6.
 

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Über Genius
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I'd do a v6 long before a straight six. Simply for a few reasons.

It's a cleaner looking install when done right.
It keeps the weight distribution better
WAY more options of engine choices.
Parts availability.
Overall rodder community support.
 

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What / Which 6 cylinder CIH engine will mate with the getrag 5 / 6 speed trans and drop and fit into the Opel GT?

I blew the rings out of my 2.0 Opel engine and 4 speed racing autocross and need to upgrade / repair it. Definitely need a 5 speed trans for sure.

I'm looking at the Miata engine and 5 speed swap but so far I haven't found one that is completed so a little hesitant.

Thanks,
Dick
There has been lots of opinions provided already, and it is up to you as to what you are trying to achieve and what you have to start with.

First off, no I-6 will "drop and fit into the opel GT". Nor will any non-4-cylinder CIH, and the Euro only 2.2/2.4 have heads that require different intake manifolds than the 1.9.

Do you have access to a CIH six? They are virtually unobtainable in North America. Commodore A's and Rekord C's even less so. Six speeds that fit a CIH? None from the factory, but with a mating plate, sure, it can likely be done. But not a "drop in".

The reasons given for a domestic (or even an import) V6 over an I-6 are sound. But ANY non-4-CIH requires extensive modifications.

A Miata engine and 5 (or 6) speed seems to sound like a good thing. Or the Euro-only 2.0SE OHC. Except the extensive modification part.

You have a 2.0, or is it a 1.9 bored to 2.0? In either case, get the crank welded and off-set ground for an extra 1/2" of stroke (1/4" in one direction), bore the block a bit (Chevy 305 0.030" over, shaved to fit the deck, fly cut to fit whatever valves you chose), stock forged rods modified to fit the pistons, clearance the block a tiny bit for the extra 1/2" of stroke, change to a steel oil pan with a few new dents and matching oil pick up, upgrade to big valves (if you haven't already), convert to a S-10 clutch and Getrag 240 5-speed or the aforementioned T5, balance the rotating assembly, and you have a very capable 2.4. Upgrade the fuel delivery to either EFI or bigger carb(s), and you have more power than you'll be able to handle, without a bunch of body modifications.

JM2CW
 

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Tazdbs 71 Opel GT
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186 Posts
Cost and power

Well, forget the I6 swap. Right now I have a complete 2003 Miata MX5 with 87,000 miles that I bought for $3,000. It has 150 hp and a 5 speed. A getrag trans with need parts to connect to the Opel block is about $2,000 total. So upgrading my 2.0 to a 2.4 will cost me over $1,000. So I can use the engine, trans and wiring, etc. from the Miata into the GT and the sell the body for at least $1,000 to my friend that wants it for an LSx swap. So for $2,000 I have 150 hp, 7 to 8,000 rpm redline and a 5 speed. Sounds like a win win to me. I already have the engine and transmission mounts.

My current Opel block is a 2.0 with Isky cam,$1,000 big valve head from OGTS (including cam), sprint header and weber 38 carb and petronix ignition and super coil. Compression is 145, 100, 70 and 50 so it needs new rings. It will be up for sale after I get it removed from the car.

Then of course the is the V6 and going electric......
 

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I'd do a v6 long before a straight six. Simply for a few reasons.

It's a cleaner looking install when done right.
It keeps the weight distribution better
WAY more options of engine choices.
Parts availability.
Overall rodder community support.
I guess beauty is in the eye of the key holder. Lol. I’ve seen pictures of a few German I6 CIH installs and some look like they came that way. Really neat and tidy.
I do love the straight 6 sound. They just subs right.
If I were going to “go big” I’d go with a Euro sources I6 CIH
 
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