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Thread: 263 Piston Size

  1. #1
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    263 Piston Size

    I tore down a 1953 263 to see if it needed anything before I drop it into my 1951 Special.

    Everything was fine, except two cylinders had broken compression rings.

    My calipers aren't precision enough to measure out to 3 decimal places and I'm not so sure about it's accuracy of the last digit with two decimal places, so I'm not able to determine if it has standard pistons or .005 oversize.

    The pistons have part #1318467 cast into the side by the wrist pin. They also have "Alcoa LO-EX" and the word "Buick" cast into them.
    Can someone please tell me by the part number if these are standard pistons? or oversize, and by how much?

    The clearance on the bearings checks out in spec with plastigauge, and again, I can't measure the crank journals accurate enough to know if it's been reground, and don't need to know, but I'm curious if anyone can tell me if rod bearings with "GMMA 905" stamped into the backside are standard or oversize?

    One last question - where is a good place to buy rings?

    Thanks!
    Dave


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    My oldest parts book, (1960) shows all OE pistons starting with "139XXXX". I don't notice 8467 in any suffixes. Could be mine is showing a changed up number...


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    My books are no good either. The parts books don't help because Buick only sold pistons and pins together as assemblies which had their own part numbers. The 1318467 number also showed up on another '53 263 piston in a post here years ago.

    www.teambuick.com/forums/archive/index.php/t-6166.php

    The pistons in the '53 straight eight are one-year-only, so they won't match what's in the '51 being pulled. There's a slim chance the engine was originally built with .010 oversized pistons. If so, there will be a 1/4" long dash after the engine serial number on the block. My guess is the pistons are still std size. The std size piston/pin combo would be 1390970

    One other idea is to check for numbers on the compression rings: std = 1339200, .010 os = 1341351 etc. Ring part numbers are the same for '51 263s.

    The connecting rod bearing insert will have the undersize dimension marked on the outside near the tang. GMMA is a common GM bearing prefix used in that era. 905 looks to be the tail end of the part no 1393905 for a std insert. 1393906 is a .001 under size. 1393907 is .002 us etc.
    Last edited by TODD; 09-11-2018 at 04:18 AM. Reason: add link
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    Thanks for the info Todd. I will check the rings for a number.

    I tried a websearch on the pistons and came up with a different number Alcoa LO-EX pistons for Chevies and there was mention of an oversize dimension stamped on top of the piston. I looked and there is a long narrow flat upraised area on top of my pistons that looks like it is there to stamp info on and it looks blank, probably meaning standard. I'll clean the thin coating of carbon off and see if anything appears.

    I searched online for a calipers that is more accurate than mine and found one in stock at a local Autozone store that is digital and claims + .005 accuracy, and it's only $12.99, so I'm going to buy that today to get a better measurement of the pistons, but at that accuracy, if they are .005 over, I still won't know for sure. The calpiers I have now only measure to + .01 accuracy.

    Any suggestions on best place to buy rings? Maybe Kanter?....they have a set for $103.88, or I see NAPA has a set of "Sealed Power Economy" rings for $114.99 - I'm thinkin' it may be nice to get these from a local store in case there is a fit problem.
    Dave

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    1953 pistons

    Dave, you have been given some good advice, both here and on the other sites. And , obviously, not all exactly the same, though similar.
    I kind of agree with Willie over on the BCA site. Take a couple pistons to an automotive machine shop. They can measure everything with instruments [ micrometers ] much more accurate than calipers.

    Todd, I was/am aware the '53 head is a little different but plead ignorance on the pistons. Care to elaborate?


    Ben

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    Thx for all the info.

    Ben - I got the same idea this morning and took a piston to my local NAPA store - they hauled out a precision calipers and determined the pistons were standard. I ordered rings from them while at the store too - will be here in 3 days. There was very little ridge for me to ream out of the cylinders.

    Dave

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    '53 piston for F263

    Ben,
    The piston chart in the parts catalogue caught my attention where it shows the '53 pistons have their own part numbers. There are a few paragraphs in the '53 shop manual explaining that the head and pistons are the only engine parts that changed from '52 to '53. The upgrade gave increased compression ratios and a few more HP. See attached images.
    Attached Images Attached Images
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    Quote Originally Posted by outbdnut View Post
    Thx for all the info.

    Ben - I got the same idea this morning and took a piston to my local NAPA store - they hauled out a precision calipers and determined the pistons were standard. I ordered rings from them while at the store too - will be here in 3 days. There was very little ridge for me to ream out of the cylinders.

    Dave
    Your really need to get the cylinders checked too. Sure, it is OK to ream the ridge, hone the cylinders, replace the rings and go. But what if someone already did that once or twice already? Broken rings are a sure sign that there is severed wear from excessive taper in the cylinders.

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    Quote Originally Posted by 322bnh View Post
    Your really need to get the cylinders checked too. Sure, it is OK to ream the ridge, hone the cylinders, replace the rings and go. But what if someone already did that once or twice already? Broken rings are a sure sign that there is severed wear from excessive taper in the cylinders.

    Thx for the warning. I checked the cylinders at the top and there isn't much wear. I'll take a chance because this car will not be driven a lot (500 miles/year at most) and the car is not worth the cost of re-boring and buying oversized pistons. If this goes bad in a short time, I have a good running 248 out of a '50 Buick I can drop in if I add the custom parts necessary to modifiy the end of the crank to accept a flywheel, as the '51 Special I'm putting it in has factory 3 on the tree. I plan on doing a mild custom on the car - mainly bucket seats from a newer car, carpeting, and a two-tone paint job. Painting is the job I like doing best on old cars.
    Dave

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