John S Posted October 1, 2023 Share Posted October 1, 2023 I’ll try not to drag this out. Looks like I have to replace the rear main seal L 48, 350 two piece rear main seal. Been close to 30 years since I replaced one, I replaced a total of four, had good results with three of them. Years ago I would dip the upper seal in oil. Use the provided little plastic tool, roll the seal into the block so the ends were flush with the block. Installed the seal in the cap wipe off the oil and put a little bit of sealant on the bearing cap and torque down. I have seen some videos where the upper seal is rolled into the block, and the ends are not flush, they are uneven. One protrudes below the block, and the other end is in the block. When installed on the bearing cap, it matches the upper seal and the seams of the seal are uneven inside the block and cap. Is this the new way to do it? Is any sealer used on the seal and the bearing cap? Correct me if I’m wrong but years ago I remember there being some glue or something on the ends of the seal that you did not want to clean off, and when they mated together, that was supposed to form a seal. I’m sure some of you guys have done these recently. Please let me know what the best way to do this is. John S Quote Link to comment Share on other sites More sharing options...
MC1of80 Posted October 1, 2023 Share Posted October 1, 2023 Forget the old rope seals. They make now a 2pc seal that is like the balancer seal or an axle seal. Rubberized and shaped like them. Take a look into them. Way easier to install also. Also a one piece oil pan gasket. Way less leaks than the gaskets of old. 1 Quote Link to comment Share on other sites More sharing options...
John S Posted October 1, 2023 Author Share Posted October 1, 2023 40 minutes ago, MC1of80 said: Forget the old rope seals. They make now a 2pc seal that is like the balancer seal or an axle seal. Rubberized and shaped like them. Take a look into them. Way easier to install also. Also a one piece oil pan gasket. Way less leaks than the gaskets of old. From what I remember the ones I replaced were not rope. They were the two piece seals. I know it’s tricky at times where the seals meet together to stop leaks there. I couldn’t remember if sealer went on the seal or just on the cap or are they rotating the seals in the seal bore. The only rope seals I remembered with on Pontiacs. Some of the old-timers I worked with many years ago, now I’m an old timer, used to dip the seals in oil to help them slide in easier. I don’t know if that is the way to still do it. Quote Link to comment Share on other sites More sharing options...
MC1of80 Posted October 1, 2023 Share Posted October 1, 2023 38 minutes ago, John S said: From what I remember the ones I replaced were not rope. They were the two piece seals. I know it’s tricky at times where the seals meet together to stop leaks there. I couldn’t remember if sealer went on the seal or just on the cap or are they rotating the seals in the seal bore. The only rope seals I remembered with on Pontiacs. Some of the old-timers I worked with many years ago, now I’m an old timer, used to dip the seals in oil to help them slide in easier. I don’t know if that is the way to still do it. Ahhhh, gotcha. Still the same procedure. Years ago before the "seal" was as common as they are now, when I assembled my father's 455 Pontiac the practice was to use the seal from a 429 frd. Had to cut 1/4" from both halves and stagger the halves with a slight dab of silicone on the ends. Maybe try the same staggering on your new seal so the halves don't match up with the main cap and possibly prevent a future leak. Quote Link to comment Share on other sites More sharing options...
MC1of80 Posted October 1, 2023 Share Posted October 1, 2023 1 minute ago, MC1of80 said: Ahhhh, gotcha. Still the same procedure. Years ago before the "seal" was as common as they are now, when I assembled my father's 455 Pontiac the practice was to use the seal from a 429 frd. Had to cut 1/4" from both halves and stagger the halves with a slight dab of silicone on the ends. Maybe try the same staggering on your new seal so the halves don't match up with the main cap and possibly prevent a future leak. Kevin took the "flip flop firebird " to the show today. This is my father's 455 and trans I assembled about 20yrs ago. Still going strong and no main leak. 2 Quote Link to comment Share on other sites More sharing options...
John S Posted October 1, 2023 Author Share Posted October 1, 2023 1 hour ago, MC1of80 said: Ahhhh, gotcha. Still the same procedure. Years ago before the "seal" was as common as they are now, when I assembled my father's 455 Pontiac the practice was to use the seal from a 429 frd. Had to cut 1/4" from both halves and stagger the halves with a slight dab of silicone on the ends. Maybe try the same staggering on your new seal so the halves don't match up with the main cap and possibly prevent a future leak. That’s what I’m talking about the lip type of seal. I’ve seen now that many people stagger the halves whereas years ago they did not. It’s a little bit of work to get one in especially laying on your back, but no one wants to do the job twice. 1 Quote Link to comment Share on other sites More sharing options...
John S Posted October 2, 2023 Author Share Posted October 2, 2023 One last question which seal is better, the rubber or silicone? John S Quote Link to comment Share on other sites More sharing options...
MC1of80 Posted October 2, 2023 Share Posted October 2, 2023 More of a personal preference but I feel the silicone is better now a days due to everything rubber seems to deteriorate quickly. Too quickly. 1 Quote Link to comment Share on other sites More sharing options...
John S Posted October 2, 2023 Author Share Posted October 2, 2023 Thanks 1 Quote Link to comment Share on other sites More sharing options...
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