Bore Distortion

[mtrehy]

Hi,

I'm interested in peoples thoughts about a block that I have been looking at. It's an oddball part-complete restoration project from a deceased estate. The deceased previous owner was a bit of a hoarder and also a significant tinkerer.

It's an american V8 (original bore 3.5625"). The engine was part assembled and has had a big overbore and new (3.72") Ross pistons & rods, some professionally ported big valve heads, reground crank, new cam etc. Clearly the engine has not been run since these new parts were installed. Anyhow, I didn't want to trust it was put together correctly so pulled the heads and sump off to give things a bit of a check over. Bores look ok at a glance - some honing marks are visible but checking with mercer bore mic shows what I assume is ok running clearance side to side (around 0.003" +- 0.0005 on all 8). Strange thing is though that I am getting consistent measurements front to back between 0.008-0.009.

I have a couple of other blocks which I think are unmolested so will be sorting out one of those but would be keen to know what could cause such a big variation - I assume this block was bored to match these new pistons and as the pistons have never been run I would guess that it must have left someones machine shop like this. I'm not sure how this would even be possible.

It seems very odd that someone has spent a vast sum of money on rods, pistons, heads etc but ended up with such a messy block. There were 2 large gouges in the block face between 1&3 and 5&7 that I can only assume were caused by someone levering off a head with 2 pry bars at some point.

Any ideas anyone?

Cheers.

[mtrehy]

There's some honing marks visible but not at a particularly nice angle or uniform. It's a bit of an odd-ball project in that it's a job lot of 3 rare cars, boxes and boxes or spares often with multiples of the same thing - I've got 10 spare cylinder heads etc. The guy was a enthusiast, hoarder, tinkerer. I do wonder whether he did something diy to this block as I found a bit of paper with 1-8 piston micrometer measurements and also a very cheap 3 leg honer in a box of random rubbish - would be surprised if even a total clown could have taken so much out and it be so oval but who knows.

I don't think a torque plate or temps could make that sort of difference - it's 0.005" bigger front to back than side to side and quite uniform across all cylinders on both banks. Only thing I can think is the spindle on the boring bar could have been misaligned or worn and allowing some play in the longitudinal direction.

Anyhow, I've got another block which is now at a machine shop that I know so hopefully can use the good rods, pistons etc on that block.

Cheers

[mtrehy]

Mitutoyo 3-4 and Mercer bore gauge. Pistons measure exactly as per the Ross data sheet that I found in the boxes. There is some variation (within 0.001) top middle bottom but nothing like the consistent difference front to back.

Block is scrap - it's not rare enough to worry about. I was really just interested in how it could be so oval as I've not seen a block that extreme before.