A Missing Chunk of Block

[NCT1111]

I have a freshly machined thin flange block with an overbore out to 1330. It is missing a chunk of the block from the bottom of No.2 cylinder bore as can be seen in the photos. It has apparently been like that for a very long time and been run with the missing piece apparently no problem prior to it being re-machined.

Any expert opinions on whether I should be concerned using the short block like this? I plan to mate it to a very nice straight cut 333 box so if something goes wrong it could be very painful.

[Dearg1275]

Why not just round all the fractured edges to relieve any stress points? This would also reduce the sharp edge of the newly machined bore and reduce the chance of the block planing the skirt of the piston and shedding aluminium filings into the gear case.

It’s not ideal but will probably run for a long time with no major issues. However it is not a block I would be looking to use in anger (as your installing of a straight cut gear set suggests). If it has had one “incident” bad enough to cause that fracture what other stresses have been induced in the block and perhaps further micro cracks?

D

[woodypup59]

Looks like that chunk has been missing for a long time.

I guess its not lurking in the gearbox somewhere ?

[251 ENG]

Could be worse!

[Peter Laidler]

In my experience with somewhat bigger blocks, I agree with Dearg and Woody. Look for the missing piece deep within the bowels of the gearbox and I'd chamfer or round-off all of the sharp edges with a small radius (a dremil will do this perfectly) while protecting the bore etc from the dust. While the piston is at the very bottom of its stroke there, the only directional force is directly UPWARDS as opposed to any side loading. Like Woody implies, '.....it's been like that for a long time without mishap so far.....' I think that it'll last forever - but that's only my opinion of course.

[Herbert]

I had a block exactly the same as yours. I chamfored the rough edges and it lasted for absolutely yonks. On the next rebuild, I had stepped liners fitted and the block is still working now!

[GraemeC]

I wouldn't be surprised if its always been like that since it was originally bored from a cast lump. I'd be VERY surprised if you found the missing piece.

[NCT1111]

I have never used this block since I got it years ago, and got it as a bare block so I have never had a chance to look for the missing piece in a gearbox. I agree that I should grind of the shape edge that runs against the piston surface.

And Graeme, like you, I suspect that is may have been like that from day one. But if it was a defect in the casting or factory machining process I wonder if they would still see it as acceptable for use?