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1931 Plymouth PA Piston problem

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Hi All

I am a junior member and currently assembling my engine. i have encountered a problem with one piston and need advise if new pistons are availble. If availible, where can I get them. I would also appreciate if any one can advise on what is an acceptable repair method to have the current piston used again.

The markings on the top of the piston is P21 and has a number 10285. On the face ot also shows max OS 0.020 which assume is that tit is 20". The specs in the owners book indicate that it a 3 5/8 bore.








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Did you try Egge machine? Google them. They have some pretty hard to come by mechanical parts.

Beat me to it.

I will add this though, the pistons manufactured by Egge are unlikely to be exactly the same weight as those you have. So you should buy a full set with rings supplied for the new set.

And, sad to say, many years ago when I purchased a full set of pistons from Egge I found the weight variation between them to be larger than the repair section of the operator's manual called for. So be ready to have them balanced.

Your best source for general repair instructions for your car is the original operator's manual (they did not start issuing factory service manuals until 1934). So if you don't have one, check with the old car literature people to get one. I know for 1933 there are reprints available for a pretty low price and I am guessing that there should be reprints available for the PA.

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Thanks to all for the advise I have made contact with Egge and await their response. I also did not know about the balancing of the pistons and that info is very useful which Egge will be responding to me on.

I received my owners manual that I baught on ebay and am very pleased with the info contained within.

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My guess is that the problem shown may be in one or two more of your set

Measure the ring groove at several points around the piston

Egge's pistons maybe OK but be prepaired to measure the skirts for flat spots This means a surface plate and dial indicator

Pistons are cam ground so don't let that worry you it's flat spots you look for

When there correct it's good but when not you may have problems

And get the set balanced if weight difference bothers you

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As stated above, you may be able to balance the pistons to match. I bought what was represented as a complete set of 6 matching NORS aluminum pistons from an unscrupulous ebay seller, only to find that 5 matched, with a 6th that was completely different (diameter, number of rings, etc.). I bought one piston from Egge which turned out to be lighter than the other 5. The machinist added some weight to the inside of the hollow piston pin to make up the difference.

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