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Block question


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Still battling with my machinist, and getting the impression that I may never get my block back. 


So trying to come up with a back up plan. I have my e30 m10 sitting between the framerails of my EFI / 5spd donor car so wondering if I wouldn't be further ahead by simply taking that block to a different machinist and getting it machined to fit the bigger pistons 


Any reason this wouldn't work? 

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There's some evidence that the E30 block has less metal around the bores. 

There is also real evidence that it has less bore shift, meaning you stand less of a chance

that you'll find water (or water will find you) when you overbore.


But the E30 block should be ok to 91, , it's lighter, it should be stronger- if you haven't paid the machinist,

I don't think anything would go wrong with the E30 version...




"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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The 1.8 block should be ok at 91mm but if you are planning on running more than 10 psi of boost I would consider doing a sonic inspection of the cylinders to make sure they are thick enough.  I have seen a few with just enough core shift that I would not make a race engine out of them at anything bigger than 90mm.  They are lighter mostly because they got much better at casting them so they did not have to "over build" just to cover the variations in the casting process.  As such I believe a older (8.5 lb heavier) block is probably stronger if you can find one that is not shifted too much.  I have seen a couple of 92mm engines crack cylinder walls in high RPM race engines.  You also will have more trouble with headgaskets the larger the bore you use.  A 91mm bore only leaves 9mm between the cylinders and when you start adding boost the gasket between them can start to move (if you get ANY DETONATION you will kill a headgasket in a heartbeat). 


What is keeping you from just going into the machine shop and asking for your block back?  If he isn't working on it he will probably be happy to not be tripping over it either. 

1970 1602 (purchased 12/1974)

1974 2002 Turbo

1988 M5

1986 Euro 325iC

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Have been back to the shop numerous times over the last 4 months. At first it was to check on progress, and then after 3 months it started becoming "I want my block back" to which he replied that it is boxed for him changing shop locations. It is apparently in the back of the sea can behind other stuff that makes it almost impossible to get to. Crossing my fingers but want to be ready if this doesnt happen. Will do some research on the e30 block as I know there are lots that throw turbos on them in the E30 chassis Cheers folks

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