Saw this in a FAQ on olds blocks.
Anyone know exactly where to look for the dreaded "O"?
Is it on each of the lifter bore bosses? Just one?
I'm about to buy a 455 to rebuild and seller has provided nice pics.
Would also like your comments on what you see. This will be my first rebuild.
The motor apparently spun a rod bearing (crank section shown in pic 1056)

[Copy from Olds Blocks FAQ;
With any block, watch out for the 'O' stamp on the lifter bore boss,
indicating a 0.010" oversize lifter. Either Oldsmobile would only have stock
0.010" over replacements or THERE ARE NONE AVAILABLE. Which means you either
get to sleeve the lifter bore (difficult and expen$ive), or scrap the block,
or, re-use that old lifter. Resleeving the lifter bore is not fun.
[ Thanks to Chris Witt for this information ][/B]


Rootney

 

It would be stamped around the hole where the lifter slides into the block. That does not happen very often. You can also mic the lifter diameters to see if any are oversized.

 

I ran into this on a 79 HO 350 motor and there were no markings anywhere on the block. It was only discovered by measuring the lifter bores. Aside from installing a sleeve in the oversized lifter bore to bring it back to a std size, Mondello will make a lifter that will work in that .010 oversize bore. It's based on a Ford lifter and it will require a different length pushrod which Mondello also provided. I think the custom lifter and pushrod was around $100 which isn't cheap but it was cheaper the what the machine shop wanted to sleeve that lifter bore. It's worked fine for a number of years now.

 

The one time it happen to me, there was a white paint mark arrow with .010 pointing to the lifter bore.
I still have that block and now know how to fix it.

Gene

 

I'm guessing its pretty rare for an oversized lifter, I have been involved with probably 25-30 Olds engine builds over the years (and who knows how many blocks I have scrapped) and have never seen a oversized lifter bore.