Rear Main Seal
 

What rear main seal is everybody having the best luck with.

Best graphite rope seal for me. Bottom of page- https://bestgasket.com/about-our-products/

BOP 1 PC seal.After that the Best Gasket rope.Tom

Graphite Rope Seal...... stock crank

Concur. It's been awhile since I've put in a graphite seal. Only resort to them if there has been a large cut to straighten out the main journals. The graphite rope seal does adapt itself better to oval situations, otherwise definitely prefer the BOP 1-piece seal.

In the least the one piece seal cuts down on possible places a seal could leak by 50%.

For assembly thought it does require another set of hands to guide the seal in when dropping the Crank in.

I learned the hard way doing my first 1 piece a few months ago. When they trim the caps to line bore an hone the block they dont address the rear seal groove for that. So now you have a more shallow groove in the cap then the one in the block. This becomes a problem because it now will make the seal off center to the crankshaft, making the cap side tighter then the block side at the lipseal. So before you start triming it you have to measure down with a straight edge at the block groove and the cap groove and trim the seal accordingly for each side of the seal for the correct center.. Im not saying that the 1 piece is bad. I know plenty success stories. Its just more involved then i thought and was overlooked by "me". So i just wanted to share what happend to me. One way to do this also is , if you have a 2 piece seal you can put 1 half in the block and measure what protrudes out. Then with the same have measure it in the cap. Compare the differences and you will know where you're at...

Of all the seals available now, which would be the easiest to change with a motor that’s currently assembled? I’ve got a 455 sitting on the stand that will one day go into my 74 Firebird. Has a bad rear main leak. Can a guy just remove the rear cap and snake the rope seal through there?

Not sure about the rope . I would think that would be real tough. But the BOP can be done know problem . Ive done it.

When Joe Sherman did my first 1 pc seal he hung the crank on his chain fall above the block and after installing the seal he lowered it into the block.He was a one man operation and figured a way to do it by him self.RIP.Tom

Rope seals have to be “fitted” in their receiver groove, carefully. No real way to install a rope seal in an assembled engine...without at least partially removing the cylinder and...

I installed a rope seal in an assembled engine. I took all of the main caps off, pried the crank up high enough to remove the bad seal. Then I worked the new seal in. Once I was sure the seal was sitting in its grove, I tightened the front 4 main caps, which packed the seal in. Then I just trimmed it, fit the seal in the main cap and finished up the engine. It might not be the correct way to do it but it runs leak free. If you are using a rope seal, a Best seal is the only way to go.

Best Gasket seals don't like aftermarket cranks with coarse serrations .They tend to melt and stop sealing.
Poly seals don't like coarse serrations either. You get poly-rubber dust as the serrations grind away the seal. You don't notice until the seal starts leaking and you pull the pan for repair.
Please check your aftermarket cranks to see if the serrations are as smooth as a stocker.

With the engine upside down on the stand, pan removed, and the main bearing caps removed, the crank can be lifted up about 5/8" before the rods bind in the block. Cherry picker and a strap will hold the crank up. Not my favorite method because it's difficult to fully clean the groove and the anti-rotation holes and get the new rope seal in place. Also a problem with the Viton seals getting the holes cleaned and filled with a little silicone so oil doesn't get past the seal.

Method #2 is to remove all rod caps and tap the piston/rod assemblies down to resting on the heads that are still in place. Requires just a little manipulation pulling the crank since the rods that are on the journals close to the block want to hang up a little. Turning the crank while pulling it out will get around this. Once the crank is out you are back to dealing with things just like a new installation.

Getting the crank back in requires carefully pulling up the piston assemblies and setting them on the rod journals as you finesse the crank back in place. I've pulled three engines of club members and did the repair as described above. The crank pull is more work but gives full room for getting the seal in correctly.

Also, as Ken said above, take a good look at seal position when you pull off #5 cap and see if the serrations might have been the problem. if it is, well you will have the crank out and can have the serrations smoothed out at the local machine shop before putting things back together.

Photo is from 2011 of a friends '72 455 HO engine. Rope seal back in and as far as I know it's still not leaking. You have to look close to see the rods.

Trying to do a bandaid fix is chancey and may wind up being a waste of your time, efforts, and money only to have to re-do what you should have done from the beginning.

#1. Read the enclosed Bulletin first. Photo 1.

#2. If the mains have been line honed, you will have only aggravated problem #1 from above in the Bulletin, so the main cap grooves should be checked to ensure the rear main seal grooves are equally concentric .

#3. Most of the 455 cranks I have seen or heard about (to include some of the aftermarket cranks) will have small serrated-like cuts on the crank's main cap journal. This was to provide a slight amount of oil to be captured and lubricate the rope seal. These serrations, depending on how aggressive they may be cut, will tear into an aftermarket VITON rear seal. The serrations need to be "knocked down" using emery cloth and made smooth so as not to dig into the Viton seal. Photo 2.

#4. I used the BOP 2-piece seal without issues on a previous 400CI build. You do need to follow the directions and use a silicone sealer as instructed to make the seal work. The seal needs to be installed in a specific orientation and if flipped backwards, you'll get leaks. The seal requires a specific "stick out" when trimmed. I recall I got a spacer that was used in trimming the seal with a razor blade. Put a light coating of oil on the crank journal and let it set-up for 24-hours.

#5. Due in part to the serrations on the 455 crank, it has been suggested to go with the rope seal, but use the aftermarket graphite rope seal - not the one that comes from a rebuild kit or local auto parts store.

#6. Can you install it with the engine together and slip it under the crank? Yep, as outlined by others. But, get it wrong, out of alignment, not seated correctly, or don't address the serrations IF you have them, and you can count on doing it over or live with the leak.

#7. Make sure you have the oil pan corner reinforcements at the rear of the pan. You can develop an oil leak if these are not used or have gone MIA. You may think you have a rear main seal leak, but it was the pan leak all along. Photo 3.

#8. Some builders have had problems with the aftermarket stock oil pan leaking at the rear. The round contour may not fit tight and crush the rubber style seal that most use. Many oil pan kits will have the cork seal and these are said to be a better choice, but can still leak and may require some re-work of the aftermarket pan. So be aware of this and check your fit.

#8. I have read both success and failure stories with the VITON seals, so it can be a crap shoot in my opinion. Have not really read any problems with the graphite rope seal. So be aware of the rear main seal grooves may not provide a perfectly round groove to set the seal into and this can pose a problem with sealing and thus leaking. The rope seal may be a better choice in this case. If your crank does not have the serrations, then the VITON seal may be better used providing no concentric issues with the seal grooves it will fit into.

Thanks Charlie for this. I have a BOP 1 piece and a block with billet caps so it has been align bored and honed. All caps are billet except for rear main.
I think it might be best for me to just run the BEST graphite rope seal and be done with it. Even if I do all the checking and trimming like you posted there will always be this "what if" I did not get it right and I have to pull the engine going on in my head.
I sold that cast Eagle crank and BHJ balancer to my brother and might as well throw in the BOP one piece. It will go in a stock block that has not been aligned honed.
One less thing to worry about.

With the one piece seal you have to split it to get it on?

Yes, there is a cut mark on it.

Looking at the website for BEST they list the 6380S seal as "67 400-428" ??????
Someone made a mistake. Also they list a seal that combines 61-66 389 (are they not the same as 400?) with the 1950s 316 and 347 engines. Didn't those come with smaller mains and why are 389s and 400s not listed together ?
Better to buy it from Butler, at least they know how to list the Pontiac engines.

No problem Troy.

I talked to Wade about this and im pretty sure he's going to change the directions of the procedure on this. If you think about it closely it makes alot of sense to measure the differences between the block side and cap. If there off by more then 0.010 and you sand the back of the seal evenly you wind up relieving more on the block side then needed. Even with the 2 piece , its says you can trim the ends to acomplish the fit. But Wade told me that he'd rather not and instead do it from the back / bottom of the seal like the 2 piece .. Usally you dont need much.. Mine was bad. My 2 piece flush on 1 side stuck out .055 on the other side of the cap and .033 on the block side ..

I used the BOP 2 piece seal on mine. Tilt test and garage floor showed no leaks