Rear Main Seal Leak

57 Handyman

Greasemonkey
Feb 6, 2017
158
43
One of the first things I recall/learned about synthetic oils was their detergent action. This ability to clean and dissolve sludge that builds up in older motors translates into leaks. When you combine the detergent ability of synthetic oils with an engine that has a rope rear main seal, what you get is a leaking seal. Rear main seal leaks in 265/first generation SBC motors were indeed a pain-in-the-*ss to fix but we--old wrench turners--dealt with them and just fixed it. That brings up the thought that finding someone who knows, has experience, AND is willing to do this job will definitely be a difficult venture!

Good luck!
 

565bbchevy

Geezer
Aug 8, 2011
8,341
113
Michigan
Every 2 piece rear main seals leak. Its guaranteed thats the main reason I dont build any old SBC's , 87 and up are the best 1 piece rear main and roller cams.
On BBC and SBC engines I clock the rear seal (Fel Pro) and dab sealer on the ends before assembly and have never had a leak, the reason I don't like a 1 piece rear main is you have to run a couterweighted flexplate even on an internally balanced engine which kind of defeats the purpose, I definitely agree on the roller cam aspect though.
 
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Jim Rockford

Greasemonkey
Nov 10, 2007
231
63
Shelby,N.C.
truth be told in all honestly, I personally haven't tried a 2 piece RM seal install since I started using Permatex right stuff sealant. so I bet it you clocked in (Knew that trick from years ago) it still was never enough for it not to eventually leak using ultra black. So i know personally right stuff is world better than even the ultra black. its a lot tougher after it cures and dont seem like it just falls off the surface of whatever you are trying to seal , reg silicone just never seemed to bond to metal like right stuff does. Hell I bet you could make a rear main seal out of right stuff sealant. lol
 
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Oct 14, 2008
7,108
113
Melville,Saskatchewan
truth be told in all honestly, I personally haven't tried a 2 piece RM seal install since I started using Permatex right stuff sealant. so I bet it you clocked in (Knew that trick from years ago) it still was never enough for it not to eventually leak using ultra black. So i know personally right stuff is world better than even the ultra black. its a lot tougher after it cures and dont seem like it just falls off the surface of whatever you are trying to seal , reg silicone just never seemed to bond to metal like right stuff does. Hell I bet you could make a rear main seal out of right stuff sealant. lol
Try their new Optimum Black and especially the 700 degree Grey. The Optimum Black is equal to the Right Stuff. The Optimum Grey totally blows away Ultra Copper. It is very heavy body and looked the same after a year on headers.
 
Oct 14, 2008
7,108
113
Melville,Saskatchewan
  • Agree
  • Haha
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Northernregal

Sloppy McRodbender
Supporting Member
Oct 24, 2017
2,126
113
Red Deer AB
Definitely more of a following.
Because they are better. 🤣🤣🤣

prove me wrong gordon ramsay GIF by MasterChef Junior
 
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Oct 14, 2008
7,108
113
Melville,Saskatchewan
Because they are better. 🤣🤣🤣

prove me wrong gordon ramsay GIF by MasterChef Junior
Nothing wrong with a Pontiac V8 from what I saw. I just run Olds because they were the most durable from the awful 70's and early 80's and we happened to own two of them, both good cars. The 75 Cutlass, everything rotted and went up in smoke, including the TH350, around the Olds 350. I would say Pontiac was right up there as well. Problem is, in Canada, as you know most Pontiac cars got the sbc and I think bbc from the factory since the late 50's. Kind of like the Olds G bodies in the 80's got the sbc in Canada, so they were few and far between, only worked on a couple. I'm an Olds 350 guy and I will put a well built, big bore, mine when it is done, against ANY small bore Pontiac 350. It is kind of like comparing a sbc 305/307 or an Olds 307 with a 5L Ford. The big bore Ford just blows them away. Now a 455 vs 455, similar bore and stroke, more apples to apples. I haven't heard as many bottom end issues on the Pontiac's, I saw one blown up Pontiac 455 but I don't know them.
 

Northernregal

Sloppy McRodbender
Supporting Member
Oct 24, 2017
2,126
113
Red Deer AB
Nothing wrong with a Pontiac V8 from what I saw. I just run Olds because they were the most durable from the awful 70's and early 80's and we happened to own two of them, both good cars. The 75 Cutlass, everything rotted and went up in smoke, including the TH350, around the Olds 350. I would say Pontiac was right up there as well. Problem is, in Canada, as you know most Pontiac cars got the sbc and I think bbc from the factory since the late 50's. Kind of like the Olds G bodies in the 80's got the sbc in Canada, so they were few and far between, only worked on a couple. I'm an Olds 350 guy and I will put a well built, big bore, mine when it is done, against ANY small bore Pontiac 350. It is kind of like comparing a sbc 305/307 or an Olds 307 with a 5L Ford. The big bore Ford just blows them away. Now a 455 vs 455, similar bore and stroke, more apples to apples. I haven't heard as many bottom end issues on the Pontiac's, I saw one blown up Pontiac 455 but I don't know them.
The poncho is kinda like an LS. Same block for everything, only cylinder bores and main journals changed. Some really decent factory castings for heads and aftermarket still makes extras. Plus aftermarket blocks exist. We did get the short stick up here in Canuckistan, they are rare.
 

pontiac guy

Master Mechanic
Oct 28, 2016
496
93
Royse City, TX
There was some funny law that drove the Chevy motors and frames under Canadian Pontiacs. I don't remember the specifics. The end result was Chevy powered Pontiacs. During the wide track days the cars looked funny with the narrow Chevy running gear under them. Of course once GM decided to homogenize the cars it all became the same and Chevy stuff ended up under the hood in the states too.
 
Oct 14, 2008
7,108
113
Melville,Saskatchewan
I think it had to do with Canadian built cars and the sbc was made here and emissions certified. The only exceptions were models only made in the US and sold in the Canadian market. All Cutlass up here in the 80's had the 267 or 305 sbc, except the H/O, 442 and 88 Cutlass being American made cars, all Olds 307 powered. The big Olds and Buick cars were Olds 307 powered.
 
  • Agree
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