263 Straight 8 Piston ID

[Outbdnut]

I just finished tearing down a 1953 263 straight 8 to see if it needed anything before I drop it into my  '51 Special.  I found two broken compression rings.   I have the shop manual and all the engine specs, but my calipers is not accurate enough to measure to 3 decimal places and I'm not so sure about the accuracy of the 2nd decimal, so I can't determine if the engine is standard or .005 over.    I think it's standard, but it's painted black, so may have been rebuilt and bored in the past.  In the next couple days, i hope to buy a better caliper locally.

 

Can anyone please tell me if my pistons are standard or oversize by the markings cast into the side by the wrist pin ends?  They have the number 1318467, and the word "Buick".  Also says "ALCOA LO-EX".

 

Also would appreciate recommendation of a good place to buy the rings, and a place to get a newer style rubber rear crankshaft seal to replace the old rope seal.

Thanks,

Dave

[Rusty_OToole]

Never heard of an engine bored .005 over. .007 was considered acceptable wear for a re ring job. There were even special rings like "10 UP" brand, that allowed for more taper.

 

Minimum rebore would be about .030 although .020 pistons were available.

 

There is a way to measure bore wear without a micrometer. Take a nail or piece of steel rod and grind it down until it fits precisely in the bottom of the bore. Use a feeler gauge to measure the gap at the top of the bore. You may be able to do this with your caliper if there is room.

[Ben Bruce aka First Born]

agree with Rusty.  Usually oversize pistons are stamped on top.

 

  Ben

[Outbdnut]

Thanks for the info guys.  Today I took a piston to my local NAPA store and they measured it with a precision calipers and determined it was standard.   I ordered rings from NAPA while I was there.  As for cylinder wear, I borrowed a ridge reamer and took out a very small ridge that I could barely see and feel.  I don't plan on putting a lot of miles on this so  putting in new rings without re-boring should be fine.   I will hone the cylinders.

 

Where I found the ".005  over" piston dimensions was in the 1951 shop manual specs. (page 2-4), where they listed dimensions for pistons at standard, and +.005,  +.010, + .020, and + .030 oversizes.  The 1953 shop manual refers back to the 1951 manual.

Dave

[Rusty_OToole]

.005 and .010 may have been available but I doubt they were used much. No rebore was necessary up to .007 and after that you would most likely rebore to .020 or .030 to make sure any wear and scoring was cleaned up.

[Spinneyhill]

I wonder if 0.005" over was a factory install if the block was overbored for some reason during the build? My Dodge has symbols stamped into the block at each cylinder, I think for build undersize of the bearings. Three are also stamped symbols each end of the engine number, which from useless memory are for bore oversize.