Hello Guys,

Looking for a good condition A12 block, standard bore (would be really happy with a 74.5mm bore). Funnily enough I got rid of my two spares about a month ago.

My block is tired, rings on piston one shattered to a zillion pieces, bores scored and there is a thick carbon lip at the top of the cylinders (which is what I think caused the broken rings). I personally thought it was all okay for a hone but the mechanic insisted that it was beyond a hone and needed a bore. A bore means bigger pistons which means I lose my floating flat tops and that I have to fork out a fortune for a new set of flatties it also means I'm pushing the block beyond factory recommended limits.

So next option is a fresh block- to be bored out to suit my pistons.

Chris

I know there is little money out there in datsun circles
yet you could use dished 76mm from the a15 slightly
machined at the top if the block needs it.
If there is money your way sleeving to 81mm has also been
confirmed possible by my engine machining after some x-raying.
I was quoted 500 for full sleeves supplied and honed once I give
them 81mm early 4age pistons.

Yeah my budget is tighter than you could imagine.

I had the hone + wash lined up for $66.00

Bore, hone and wash to 74.5mm OS will cost me $175.00.

At the moment I am dead set on an A12 block, can't afford any other options.

Looking for later A12 block by the way with the dizzie mid way along the block.

Here are some pictures anyway, absolutely convinced the carbon build up at the top of the bores was the cause of the rings failing. Open to some opinions.

Last time I had ring issues (broken into 4 pieces) was because the bore was just outside the serviceable limits. Re-used the same pistons in another (tighter) block (with just a hone) and ran a whole rally season with no problems..

The rings shouldn't touch the build-up, that is the reason it is there as the rings haven't swept that part of the bore clean.

Yep okay that makes sense.

I was thinking the ring was broken in fewer places to begin with and the carbon had started to build on the walls as it passed the broken ring. Then it all went haywire.

Your explanation makes much more sense though. Thanks for that.

My poor block went pretty hard though for three and-a-bit cylinders!

Found a block. Thanks guys.