Stock 440 Bore Diameter

[john108]

I just stripped down a 1976 -1977 440 Block.
I understand that the stock bore diameter is stated as 4.320  .
I tried measuring the bore for all the pistons with a caliper
and came up with approximately 4.312 - 4.315  .
I definitely tried to get the maximum reading possible but couldn't get anything larger.
I couldn't get to where the rings ride as the piston is well below the deck.

Question:  Are the block bores sometimes a little undersized or is it me and my calipers??

[areibel]

Calipers probably won't get down past the carbon ring at the top.  You'd need a bore gauge to get an accurate reading, and you need to take it at a couple spots to check for out of round, taper, etc..
The readings you got at the top are probably from that carbon, so it won't be all that accurate.  A sheet of paper is something like .005 thick, your reading is only about that far off from a stock bore so I'd bet you'll get a different number down in the cylinder.

[john108]

Yes
I understand that and tried scraping before measuring. 
I was just wondering if bores were ever undersized from the factory.
The block will get machined at a machine shop, but I was just wondering if it is my error, the Harbor Freight calipers, or the block does sometimes come slightly undersized.  The cylinders look pristine and I can't feel a ridge.
I guess 36 year old Chrysler Imperials with 76000 miles were not abused too much.
Thank you  --  John

[chargerbr549]

When I measure parts such as valve stem diameters, seat and bore diameters I only use micrometers and bore gauges because they are a little more solid, calipers have too much flex especially some of the cheaper ones, a little bit of finger pressure can easily change the reading on calipers over a .001"

I can't say for sure that blocks might have come undersized from the factory but alot of times when you hot tank a block that has never been rebuilt before you will see letters on the side of the block that were written on there with a paint pen I believe, that indicated if the finished bore from the factory was standard or how much oversized they were so they could match up the correct OD of the pistons to keep the bore clearance within spec or at least thats what I was told what the letters meant.

Kevin