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Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
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| | | | Joined: Aug 2010 Posts: 255 'Bolter | | 'Bolter Joined: Aug 2010 Posts: 255 | Do all 261 blocks use the "rope" seal on rear main? If not - what years used modern type seal? | | | | | Joined: Jun 2005 Posts: 388 Shop Shark | | Shop Shark Joined: Jun 2005 Posts: 388 | This question about the rear main seals has come before. The answer is not totally clear, at least to me. A rplacement 261 short block for a 1954 that I bought in 1958 came with a rope seal (that really leaked.) Another 1954 261 short block that was purchased in the early seventies came with an orange elastomeric seal. Hoyt | | | | | Joined: Jan 2001 Posts: 5,337 'Bolter | | 'Bolter Joined: Jan 2001 Posts: 5,337 | I can not clear up when Chev changed to a elastomeric seal but I know they did. I have a NOS GM elastomeric seal .
See the USA in your vintage Chevrolet! My Blog | | | | | Joined: Sep 2003 Posts: 1,820 Shop Shark | | Shop Shark Joined: Sep 2003 Posts: 1,820 | I believe ALL 216-235-261 engines came with rope seals.
"Truckin' Around .......... Since 1937!" My name is Joe and I am addicted to Classic Country Music. I just can't hep myself.Operators are standing by to take your calls! Now cruising in the Passing Lane | | | | | Joined: Feb 2001 Posts: 1,094 'Bolter | | 'Bolter Joined: Feb 2001 Posts: 1,094 | My 59 261 has the modern rubber seal.
Tommy
59 apache 1/2t
261 short stepside
| | | | | Joined: Sep 2003 Posts: 1,820 Shop Shark | | Shop Shark Joined: Sep 2003 Posts: 1,820 | I believe any 216-235-261 that has a "rubber" seal, the seal has been changed. When I built my engine in 1990, I was told rubber would not work in a 261, but the builder put rubber in without telling me. The first thing after I got the engine in the truck, the seal started leaking. I replaced it with a rope seal and haven't had a problem since. That's not to say a "rubber" seal wouldn't work, but a rope seal, properly installed and in my opinion, works best.
"Truckin' Around .......... Since 1937!" My name is Joe and I am addicted to Classic Country Music. I just can't hep myself.Operators are standing by to take your calls! Now cruising in the Passing Lane | | | | | Joined: Jan 2001 Posts: 5,337 'Bolter | | 'Bolter Joined: Jan 2001 Posts: 5,337 | I have had very good luck with the rubber/elastomeric seal.
There are two things you need to watch out for when using one.
First, if the seal surface of the crank has been turned down they will not work, use a rope.
Second, I have seen a number of blocks where the seal groove is not concentric with the bearing bore. In this case a rope seal is the only way.
See the USA in your vintage Chevrolet! My Blog | | | | | Joined: Oct 2006 Posts: 1,847 'Bolter | | 'Bolter Joined: Oct 2006 Posts: 1,847 | I had my 216 machined for a full circle seal. It just seems like the right thing to do | | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 |
When I rebuilt my 1960 261 in 1972, the gasket kit from NAPA (Fel-Pro?) came with a rope seal and a rubber seal. I used the rubber seal. However, the 1960 Chevrolet Truck Shop Manual describes (with illustration/picture) the braided rope-style rear main bearing oil seal.
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