Cometic rear main seal vs...

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70Hardtop

70Hardtop

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I was wondering if anyone has had any experience with Cometic rear main crank seals? I just bought one from US ebay (I live in Australia), it was a good price I thought at US$27.50 and only $14.25 shipping. I bought it only because of the name, as I have seen and heard that Cometic make really good quality (and expensive) gaskets. So I was hoping that quality also extends to the rear main seal.

I also have a Felpro here but was thinking the Cometic may be a better choice. I know Superformance are also highly rated (better than Felpro) but was hoping someone could know for sure about the Cometic

thanks
 
I use Cometic gaskets and they work great and you can get whatever thickness you want. Call them and talk to Jason if you have any problem and he will take care of you. I had a 440-500 inch that the guy used .080 head gaskets and I went up to Cometic and Jason had the intake gaskets made while I waited.
Living in N.E. Ohio everyplace is about 10 - 30 miles from me.
Well not everything but enough that I can get what I need.
 
brian6pac said:
I use Cometic gaskets and they work great and you can get whatever thickness you want. Call them and talk to Jason if you have any problem and he will take care of you. I had a 440-500 inch that the guy used .080 head gaskets and I went up to Cometic and Jason had the intake gaskets made while I waited.
Living in N.E. Ohio everyplace is about 10 - 30 miles from me.
Well not everything but enough that I can get what I need.
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Thanks Brian, I will call Cometic and hope I can talk to this Jason fellow. Your post is about your experience with their gaskets and yes I am aware they are high quality. I was hoping someone could know something about the actual Cometic rear main seal which is a totally different thing to a head gasket. They are twice the price as a Felpro so where are the differences? I will see what Cometic says.
 
brian6pac said:
WHAT?
You do know that you have to polish the crank to use a rubber seal. I have never had one leak if installed correctly.
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Initially I was wanting to use a rope seal, however they are very difficult to get in Australia, I am talking about the original OEM style one (which used asbestos in it apparently) and not the crap new style which has a rubber tube core and thin outer sheath of "rope" and is renown for leaking. I saw there is one OEM type on USA Ebay but it was $85 by the time it would be posted here. Several assemblers here have complained about these new rope seals (eg made by Felpro) and say not to use them as they often leak and are just nowhere near as good as the old solid OEM ones. That's why I have decided to go with the later 318 340 style seal. I called Cometic and didn't really get much extra info. I asked if there were installation instructions with the seal (as I have already ordered one) and they said , yes, there were "general installation instructions". But I wanted Chrysler-specific instructions, I think it will be best if I listen to the guys here on the forum and their experiences with installing them. Also the price difference compared to other seals is probably that the Cometic one is made of Viton, which is a tougher material than neoprene / rubber.
 
brian6pac said:
WHAT?
You do know that you have to polish the crank to use a rubber seal. I have never had one leak if installed correctly.
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That is something I would like to know - if I use this rubber seal, do I have to remove all the cross hatching on the crank that is there for the old rope seal? Does it have to be polished shiny in that area for the seal to work? I would assume it does. But then, to remove all that crosshatch, wouldn't it reduce the diameter of the seal surface and reduce the efficiency of the seal?

Thanks
 
I have polished them down and can still see the marks and they don't leak, but you got to get it really smooth
 
famous bob said:
I didn`t polish mine. They are there to direct oil back into the engine.
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thanks Bob, so that means you used a neoprene seal directly on the knurl and no leaks? I would have thought that the knurling would roughen up or wear out the seal more and so result in a leak eventually? Can you describe a bit more of your experience? I just checked another forged crank, it is out of a 1971 340, and that also has the knurling, and I'm not sure if the 71 340 had a rope seal or rubber type.
 
You won't find asbestos in anything anymore. But they material they use doesn't leak when installed properly. Last engine I did that had a leak was a lip seal, around 2001. Since then I went back to rope and have never had a leaky rear main, regardless of displacement, use, engine condition, oil, environment... These engines were designed to use it.
I'm not sure how many of us were around when they were regularly being serviced but Mopar rear main leaks and replacements were not common when I first got into cars in the mid 80s.
You can also look for any early Ford or Buick applications (early 60s). All you need is the rope. The side seals you can either use what's provided with the lip seal in the gasket sets, or silicone. I think I buy them for $9-10 each. Summit Racing lists them, and I'd wager most major supply houses down under do too. You just need to ask the right guy.
 
The area on the crank is not cross hatching, it is directional grooves. On a used crank we use fel pro rubber or neoprene or whatever they are made of, not rope. A crank that has run for many miles with a rope seal - the area is smooth, no need to buff it down more.
 
Marcohotrod said:
The area on the crank is not cross hatching, it is directional grooves. On a used crank we use fel pro rubber or neoprene or whatever they are made of, not rope. A crank that has run for many miles with a rope seal - the area is smooth, no need to buff it down more.
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That sounds like my crank, a forged one in a 1967 273, never been torn down except when I did it last year, with what looks like the original rope seal there. I actually would prefer to use a rope seal but only if I can get the original type. Although Moper says he has great results from using the new ones. I wish I could be that confident, but as I have already bought this Cometic one, I think I will use that. I was just a bit uncertain about the grooves. Yes I knew they were not really cross hatching, I just didn't know what the real name was, or how they actually worked. I thought they were designed to provide a rough sealing surface for the rope, whereas a rubber lip seal works best on a smooth surface.
 
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