The Stovebolt Site Forums The Shop Area Engine Shop which fel-pro gasket for the rear seal

We're putting together a motor for our '53 chevy truck. Its a '55 235 from a '55 chevy bel-air with a hydro-matic. We've had it completely machined. My dad called and said the gasket kit the shop put in for us is from fel-pro. He doesn't like blogs as he calls them so he won't use the site himself (I tried to tell him he could ask anything but he's funny that way). I'm repeating what he told with me, so bear with me. He's been a mechanic his whole life so he knows motors. There are two gaskets for the rear oil seal. There's a neoprene one and a rope gasket. He didn't know which to use, he said they both will fit, but he's not sure. He called the company and they told him to use whichever one came out of the motor.

His question is really which he should use and if someone's found a solution (or is the neoprene the solution) for the rear seal always leaking.

He said he did his own research (and remembers) and found that the rear seals always leak on these motors and that if you rebuild them they usually leak right away. Is there something you guys do when you rebuild them to fix that, or should he use the neoprene gasket, or the rope one? Any ideas? Just thought I'd put this out there. thanks

If the engine has shims on the rear main you must use the rope seal.
If no shims you can use either but I would use the Neoprene.

I think if you do a search you will find advice to use only the "rope" type seals in pre 56 235s. I would suggest purchasing the seal made by Best Gasket.

1955 was a change over year for 235's. Early used shims and later did not. The main bearing design also changed at the same time from dowel upper and lower to tang upper and dowel lower.

I feel like an idiot - if you'll look at any of my posts, at the bottom you'll see it says "'53 Chevy 3604 Five Window Cab ('56 235)" It's been so long since we tore this apart and did the research I forgot it's a '56. I knew the "'55" didn't sound right but it is definitely a '56.

So the question remains - which gasket do we use? The guy that machined this out did so to get rid of the shims. It has bearing now (sorry, bushings?). He's an old timer that said he used to do these all the time, and now that he's done another he remembers why he swore he'd never do another! But he's good at what he does - we just haven't spoken to him for a year and can't seem to get a hold of him now (for all I know he's not doing it anymore).

Anyway - will we be stuck with a leaky motor? Should we use the neoprene? Advice please now that I've corrected myself (sorry!)

I have had the best luck with Neoprene seals.
The only thing you need to make sure of is that the seal groove is concentric to the bearing bore. I have seen a number that are not. If it is not a rope seal is mandatory.

Pre '68 Dave,

Do you have trouble with the motor leaking oil? seems like a lot we read say it's a common problem. Just trying to see if there's anything we can do to avoid this if it's possible since we haven't put it together.

I find it hard to guarantee a leak free rope seal, they even leaked from the factory. That is not to say some do not leak. I have recently started using Best Gasket brand rope seals and so far I like them.
Through the years I have had the best luck with the Neoprene seal.
As I mentioned in my post above the seal groove must be concentric to the bearing bore. I would also offset the ends of the seal with the parting line of the cap and block. Make sure to use some Permatex on the cap to block surface to prevent oil wicking through that area.

Pre '68 Dave: Now why did that not occur to me? Just put a neoprene seal in my truck. 55-57 235 motor. Have not torqued the main bearings yet so can slip it off and set that seal off the line of the bearing cap. Great idea! Thanks!

I wish I could say I had thought of the idea but it has been around.
The offset only needs to be a slight amount.