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I am new here; and looking into a project for my GT. I would like to know if there is any info of maximum cylinder bore (safely) of 1.9 engines; specifically blocks castings from late 1960's to early 1970's? I have a few engines to choose from (in those years) and I am concern of wall/deck thickness vs core shifting (during casting). I wish not to disassemble 4 engines; send out blocks for hot tank, magnaflux, then have verify (via) eddy current/sonic NDT machines the best block candidate; (which would be the correct way to go and or have bores oversized sleeves, etc). Too costly for this and would rather spend the money on forged pistons. So if someone has a idea of optional year engine, I would like to re-vamp a 1.9 for a little more HP; e.g. larger bore.

Thanks, vince.
 

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Welcome aboard Vince,
I'm sure the info is here somewhere but finding it may be hours of looking through stuff
But don't worry your in the right site and the gods of knowledge will have an answer for you soon
The folks here love pictures of what you have and or are working on so feel free to show what you got
We look forward to it and your progress welcome to the site and thank you for keeping an opel alive
 

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I believe it's a bit over 2mm or more specifically 0.095 over bore for the 1.9 blocks.
 

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Can Opeler
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Some guys in Germany get away with 97mm and even an oddball 98mm from what I’ve read but don’t quote me. I’m sure it’s luck of the casting at that bore though.

I do know you CAN safely go above the 95mm “2.0L piston” bore we commonly use slightly. Next time I rebuild I will be going around 95.5mm so I can get a true classic race legal 2000cc instead of 1979cc.
I would risk 96mm but just go with 95.5mm if you want to think outside the basic “2.0L piston box” or upgrade your stroke instead.
 

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Opel Rallier since 1977
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The thrust walls can take it; it is the non-thrust walls (front and back) that become the issue. If you go to 96 mm ...3.78in... then those walls will get down to the .070-.080" range with minor core shift at the thinnest areas.
BTW, my local machinist can measure walls and then adjust the bore axis forward or back a bit to compensate for core shift. So you might ask your shop about that process.
I have only Sonic tested 3 blocks so have too small of a population sample to know the absolute worst case of core shift.
I will probably go to 96mm with my best block. The minimum non- thrust wall thickness will then be .080-.090" on that block. The main thrust wall will still be a ridiculous .240" + or - !
 
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