Rear main seal - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Sundrop · 10-06-2013, 02:48 PM

Is it possible to put a 1 piece rear main seal in a motor that has a 2 piece rear main seal?

cableguy0 · 10-06-2013, 03:16 PM

Simple answer is No. On 1 piece rear main blocks there is an adapter that holds the rear main seal which bolts on externally. Also the crank itself is different.

Sundrop · 10-06-2013, 03:33 PM

Ok thanks for the info!

storm9c1 · 10-07-2013, 04:12 PM

FWIW, I do know you can go the other way though. I am running an engine in a project that is a 1-piece block with a 2-piece real seal adapter. The reason for doing this is if you have a special crank (perhaps a custom internally balanced crank in a stroker for example) and you want to cheaply run it in a modern roller/vortec block. A high quality adapter won't leak and makes it easier to change the 2-piece seal if needed. Not saying running one of these is a great idea. Switching a 1-piece for a 2-piece is going backwards, but it does work if you need it for some reason. It used to be an old school (well late 80s & 90s) hot rod trick since it will expand your options if you want an internally balanced crank on a 1-piece block. Normally a 1-piece block eliminates some (or all) of the rear counterweight on the crank thus often forcing an external balance crank on 99% of the 1-piece projects. That's a little more history as to why it's hard to switch from one to the other.

Nowadays there are many more crank choices available, so it isn't as common to do the 1-piece to 2-piece conversion.

Sundrop · 10-09-2013, 03:24 PM

Quote:

Originally Posted by storm9c1

FWIW, I do know you can go the other way though. I am running an engine in a project that is a 1-piece block with a 2-piece real seal adapter. The reason for doing this is if you have a special crank (perhaps a custom internally balanced crank in a stroker for example) and you want to cheaply run it in a modern roller/vortec block. A high quality adapter won't leak and makes it easier to change the 2-piece seal if needed. Not saying running one of these is a great idea. Switching a 1-piece for a 2-piece is going backwards, but it does work if you need it for some reason. It used to be an old school (well late 80s & 90s) hot rod trick since it will expand your options if you want an internally balanced crank on a 1-piece block. Normally a 1-piece block eliminates some (or all) of the rear counterweight on the crank thus often forcing an external balance crank on 99% of the 1-piece projects. That's a little more history as to why it's hard to switch from one to the other.

Nowadays there are many more crank choices available, so it isn't as common to do the 1-piece to 2-piece conversion.

I was talking about converting a 2 piece into a 1 piece

storm9c1 · 10-09-2013, 04:36 PM

Quote:

Originally Posted by Sundrop

I was talking about converting a 2 piece into a 1 piece

Yeah, I know, hence the "for what it's worth" -- in case there were others reading who wondered if you can go the other way.

Sundrop · 10-13-2013, 02:15 PM

Quote:

Originally Posted by storm9c1

Yeah, I know, hence the "for what it's worth" -- in case there were others reading who wondered if you can go the other way.

ok lol just making sure we was talking about the samething

10-06-2013, 02:48 PM	#1
Sundrop Registered User Join Date: Feb 2013 Location: pulaski,tn Posts: 194	Rear main seal Is it possible to put a 1 piece rear main seal in a motor that has a 2 piece rear main seal?

10-06-2013, 03:16 PM	#2
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	Re: Rear main seal Simple answer is No. On 1 piece rear main blocks there is an adapter that holds the rear main seal which bolts on externally. Also the crank itself is different. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

10-06-2013, 03:33 PM	#3
Sundrop Registered User Join Date: Feb 2013 Location: pulaski,tn Posts: 194	Re: Rear main seal Ok thanks for the info!

10-07-2013, 04:12 PM	#4
storm9c1 * That's interesting * Join Date: Oct 2008 Location: Pittsburgh, PA Posts: 2,772	Re: Rear main seal FWIW, I do know you can go the other way though. I am running an engine in a project that is a 1-piece block with a 2-piece real seal adapter. The reason for doing this is if you have a special crank (perhaps a custom internally balanced crank in a stroker for example) and you want to cheaply run it in a modern roller/vortec block. A high quality adapter won't leak and makes it easier to change the 2-piece seal if needed. Not saying running one of these is a great idea. Switching a 1-piece for a 2-piece is going backwards, but it does work if you need it for some reason. It used to be an old school (well late 80s & 90s) hot rod trick since it will expand your options if you want an internally balanced crank on a 1-piece block. Normally a 1-piece block eliminates some (or all) of the rear counterweight on the crank thus often forcing an external balance crank on 99% of the 1-piece projects. That's a little more history as to why it's hard to switch from one to the other. Nowadays there are many more crank choices available, so it isn't as common to do the 1-piece to 2-piece conversion. __________________ Tom Chevy by day... 1969 Chevy C30 Rollback Tow Truck -- 383 stroker, 4L80E 2011 Chevy Caprice PPV 9C3 6.0L 1995 Chevy Caprice 9C1 1994 Chevy Caprice 9C1 #3 1995 Chevy Caprice Wagon #2 1995 Chevy Impala SS Mopar by night... 1969 Dodge Charger 1972 Chrysler Newport 2dr Hardtop (27K miles) Plus others...



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