Anyone seen this before ? cracked under centre main
Turbo Mini Forums

It is not mine, but was posted on a vintage race forum. As folks here have broken just about everything I thought it might be a good place to ask

He runs a 14 CR and 8500 rpm

cheers

JR

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That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

ah!

the evil casting hole above the centre main!!

Ive not seen a crack here, but apparently it does happen,

if using one of these blocks for high performance, you should grind it out smooth... or better yet use a block without the hole.

Presumably exactly why the blocks without that hole in the casting are in demand.

Still a substantial piece of iron to crack. Always wondered if there was truth in the block failing round that area story.

yes seen this a few times on hi output reving ......" none ballanced engine "

exactly why i'm looking for an A+ block!

I'm puzzled as to where the crack initiated.

maybe it was just a casting flaw?


apparently he has had similar crack happen on thin flange blocks twice before
(in 35 years I might add)

I would have ground everything smooth as well.

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

casting mark stress risers in that hole above the centre main,

crack will start from a rough spot, some flashing, and then propagate for some time, probably before even it was tuned, grinding it all smooth and polishing it stops it starting but on a 35 year plus block not worth the effort if it was prone to it then it will have initiated by now and grinding polishing once it has started wont help at all..

I agree that if the crack has already initiated it may be pointless trying to prevent it propagating - too much metal may have to be removed to get to the end of it which just weakens things further - but don't assume all early blocks will have had the crack initiate.
I have two early A series blocks (with the casting void) that are very low mileage but have sat in my garage for over 25 years.

A light grind/polish in that area, just enough for some DP (not sure if you could get a magnet in there for MPI) would say whether it was worth spending the time blending/polishing properly.

I just wouldn't write the blocks off because of their age and what may have already been initiated without actually looking to see.

Schrödinger's cat - so which one am I ???

The hole is not all bad. There is a certain profesional engine builder that introduces holes like that for a specific reason. They are the fastest engines on the grid!

You only have to look at Jap bike engine blocks

DP

you know you want to google it but not on a work PC. Agreed hole lightening all good but foundrymen at morris works didnt go for a high class casting in that area hence the issue, its the rough finish/sand inclusions that cause the problem..