Rear Main Seal - Rubber vs Viton?

[mopowers]

I've got both types of small block rear main seals sitting on my bench (rubber and viton). Which one do you SB guys prefer? I've only ever used the regular ol' rubber version.

 

[fishmens67]

Viton is more chemical resistant, better than the conventional rubber seal.
If you have it use it.

 

[mopowers]

Viton is more chemical resistant, better than the conventional rubber seal.
If you have it use it.

Do you still put a tiny smear of RTV where the ends meet on viton?

 

[grjammer]

I have just finished my last attempt at rear main install. Hope yours isn't as troublesome as mine was. It leaked with the Felpro seals, 440 source Viton seals, and the Fastfish one piece seal. I finally got it to seal with the Best seal rope seal. I used a small amount of RTV on the ends of all types except the rope seal. For it I used Permatex Motoseal case sealer on the retainer block and I'm sure it went over the rope seal ends a small amount.
I haven't had the car drive able yet, so don't know how it will finally end up. The Motoseal was a substitute for Yamabond brand case sealer recommended by other users here. Just my 2 cents, Hoping you have much better results than I did. I wish I would of started with the case sealer instead of the Ultra black I was using.

 

[blind bat]

I have just finished my last attempt at rear main install. Hope yours isn't as troublesome as mine was. It leaked with the Felpro seals, 440 source Viton seals, and the Fastfish one piece seal. I finally got it to seal with the Best seal rope seal. I used a small amount of RTV on the ends of all types except the rope seal. For it I used Permatex Motoseal case sealer on the retainer block and I'm sure it went over the rope seal ends a small amount.
I haven't had the car drive able yet, so don't know how it will finally end up. The Motoseal was a substitute for Yamabond brand case sealer recommended by other users here. Just my 2 cents, Hoping you have much better results than I did. I wish I would of started with the case sealer instead of the Ultra black I was using.

That sounds like a nightmare. Glad you got it squared away.

 

[Ricks70Duster340]

I have just finished my last attempt at rear main install. Hope yours isn't as troublesome as mine was. It leaked with the Felpro seals, 440 source Viton seals, and the Fastfish one piece seal. I finally got it to seal with the Best seal rope seal. I used a small amount of RTV on the ends of all types except the rope seal. For it I used Permatex Motoseal case sealer on the retainer block and I'm sure it went over the rope seal ends a small amount.
I haven't had the car drive able yet, so don't know how it will finally end up. The Motoseal was a substitute for Yamabond brand case sealer recommended by other users here. Just my 2 cents, Hoping you have much better results than I did. I wish I would of started with the case sealer instead of the Ultra black I was using.

Did you pull the crank to put in the upper seal or did you "sneak" it in with the crank in place?

 

[grjammer]

I pulled the crank. I wanted to check bearings and rings anyway. Didn't find anything bad other than I probably would of started break in with a better cylinder crosshatch. I would advise to never try to "sneak" a rope seal in. I couldn't even find a braided snake tool to purchase, and would never drag the cheapo metal pinch clip style around the journal. Pulling the crank also allowed me to check alignment of the seal retainer when torqued, which was good.

 

[mopowers]

Do they sell rope seals for small blocks?

 

[grjammer]

I don't know tbh. I probably shoulda mentioned its a 440. lol

 

[dogbreath]

340 or 360 ?

 

[mopowers]

340 or 360 ?

360

 

[dogbreath]

5.9 magnum viton double lip seal

 

[RustyRatRod]

I just put the new one piece Viton rear main seal in my Ford 400. So far it ain't leaked a drop.

 

[Bewy]

Is the seal really rubber, or just another Viton seal being called rubber. Rubber does not handle heat very well, as anybody who has stripped down an engine with rubber valve seals knows. I like the brown Silicon seals.

 

[Valman]

Important to check for size as well. It’s surprising how out of round or off size a seal can be.
You can set a telescoping/snap gauge to the crank journal size then check around the seal.