engine and drivetrain M10 Block Bore Limit?

[FB73tii]

For race engine builders--how far would you feel comfortable boring out an M10 block without sonic testing it first? If sonic tested, what is minimum safe cylinder wall thickness to look for?

 

I have heard of people going as far as 92.0mm, but I would certainly sonic test if going that far. The reason I ask is my block that was scored when the #1 intake valve dropped cleaned up at 91.0 mm (the bores were 90.25mm) and I might eventually re-use this block with 91mm pistons if I thought it was safe to do so.

 

Yeah, I know, blocks are cheap, but I did such a nice job prepping and painting this one!  Would be a shame to just toss it. Opinions/experiences?

 

Thanks,

Fred '69 & '74tii

 

 

Edited October 10, 2013 by FB73tii

[williamggruff]

Fred,

 

My M10 block has 92mm pistons.  Unfortunately, I don't know what testing Eric Kerman performed on the block during the build, as I bought the motor used.  I've heard of folks running 93+ mm pistons, but haven't seen them with my own eyes.

 

Grice

[Tommy]

Information what I have gathered is that 92mm is too much for high powered turbo application but should still be ok for N/A engine. 91mm I would consider safe without ultrasonic testing. This applies only to old 2 liter m10 block from 2002 or NK. Late blocks like something from e30 are weaker.

 

  Tommy

[TobyB]

Yeah, the odd  thing is that it depends on what you start with.  The E30 blocks are much more consistent, but there's a lot

less metal there overall.  The E21 blocks have a bit less metal- but less potential core shift, so at 91mm, you'd probably be ok.

An early 2002 block certainly has enough wall thickness- it's just, is it all where it's supposed to be?

 

If 91mm pistons aren't exorbitant, I'd try it.

 

t

[allbim]

I measured a typical minimum of .160" (4mm) cylinder wall thickness with an ultrasonic gauge and a mechanical gauge where possible, on a stock-bore (89mm) 1979 E21 block, with a variation on the plus side of up to .030". My block had a moderate amount of rust in it before cleaning. I think 91mm is OK and 92mm is really pushing it. 

[Preyupy]

I have never found a block that was not safe at 91mm even for a 13:1+ compression ratio race engine.  I have sonic checked a couple that I was not comfortable going to 92mm with but most have been safe. 

[FB73tii]

Great, thanks to everyone for your replies. I will hold onto the block and feel comfortable using it for an NA race engine someday.

 

Best regards, Fred  '69 & '74tii

[RussTii]

I've been running a stroker M10 for about 10 years now with a 92 MM Bore. Have a set of CP 12.5 C/R pistons on order so we'll see what a 2313 CC N/A M10 will do on race gas.  According to Jeff and Jeremy at I/E my Weber 45's may become the limiting factor.