So I'm putting a '55 powerglide motor in my '51 Chevy. I'm doing all (well, most) of the seals and I'm thinking of doing the rear main while its upside down on the stand. It's not leaking but i figure i may as well do it while its easiest. I have a Best Gaskets rubber seal that i want to use. I've researched this topic for more than a year, due to the leaking rear main on the '58 motor that's in the car now, which is why i got the seal in the first place. Ive read so many different things about which seals were used or were able to be used, I'm hoping somebody with a definite answer will chime in. In '55, were the blocks machined for rubber rear main seals or only rope?
I just went through this recently, Built a a 55 PG engine for a friend . I believe the Best gaskets rear main seal lists for 56 and up engines...I had a junk 57 235 block so I measured the rear main groove, and they were the same. I assembled the engine with the Best gaskets rear main and ran it on the test stand, No problems at all.
^^^^^^^^^ Confirmed … tried the Best rubber in a '55 block this summer - no fit. The seal machining operation and oil pan rail change at the same time. Just be sure to use the older "black" rope if you do change it. The white fiberglass or plastic stuff don't hold oil.
This is what's confusing me. According to my number on the distributor pad, my engine is number 0422498 built in '55 for a pg. Now I dont know how many were made, but according to my research my block number wasn't used on '55 pg cars. The block and head numbers are correct for '55 trucks, but my block has the oil passage hole above the rear cam freeze plug. They did use my block on '56 pg cars however so maybe my motor is a late year production . The guy I got the motor from had another one beside mine with the same block and head number, with the pg adapter and all still on it. The odds of both motors, from two different sources being the wrong combo but the same as each other are pretty slim so it must be factory. The oil pan is straight on one side and bumps out on the other. Does that tell you anything? Here are all my numbers
So could it have been used in a '56 car with a leftover '55 head and should a rubber seal work? I really dont wanna pull the cap off if it only takes a rope seal.
it was used in a 55 car, not a 56 car. you can tell because it's stamped with a 55 number. And they didn't leave blocks sitting around for half a year--usually a few days, maybe a week or two. rear seals on a 235 are a bitch.
is there a difference? I thought they were all machined for rope seals, and you can get a rubber seal that might or might not work, depending on how well they machined the block. My son's pickup has a 1957 235 that a rubber seal kind of works, (tried two of them), but it still leaks some. There was no need to make the groove concentric with the bearing bore, with a rope seal, so they didn't seem to bother. If the dimensions changed, it was not to make it work with a rubber seal, was it? The 1959 chevy parts book only lists a graphite impregnated rope seal for all 6 cylinder engines, 1940-59. Even the V8 didn't get a rubber seal until mid 1959, and that was a totally different design, the machining was quite different, not just a dimension change.
Yeah, it was confusing for me too and I talked to my machine shop about it as far as the 1956 and newer listing. They said they had used them in earlier engines with no problems ,and as I said I could not see a difference on the 57 block I measured. The seal seemed to fit the groove just fine and as of now the engine has a couple of hours run time and no leaks so far.It was just installed in the 51 PU last week and its not on the road yet. Neat little engine had Schnieder grind up a cam and used the 848 head with two 1bbls and split exhaust.
Unfortunately I'm still in the same boat I was in. It may or may not work. I guess I'll hold off on touching the seal
It depends how bad the leak is. If it's pretty bad, then the rubber seal will likely help. Even if they don't list it for the year engine you have. Keep in mind that catalog applications listings are not always accurate...
I don't think it's leaking at all. I just wanted to change it as preventive maintenance. It didn't think the seal was leaking on the '58 motor either but when I put it in I was sorely mistaken
The Jalopy Journal
