[Verdoro 68]

Tore down the short block this afternoon. As far as I can tell, the one piece seal developed some kind of a kink in it on the side during installation that contributed to the leak. Maybe I didn't trim it enough or have it seated good enough and it compressed funny.

At first glance, the two piece seems to fit the radius reasonably well, but it's going to need to be trimmed quite a bit as around .025 is sticking out of the block and a little less on the cap. I could give this two piece a try since I've got it on hand, but I'm wondering if the graphite seal is the safer bet since I rarely ever hear about them leaking.

[Verdoro 68]

I pulled the crank out last night - so much fun undoing all the work of the last month!

I've been trading emails with Wade at BOP, I really appreciate his responsiveness. He described the serrations in my crank "aggressive" and relayed some concern about a graphite seal working in my siutation. I can't catch them with my fingernail, but they do make a washboard sound when I run my nail over them.

He had me measure the diameter of the sealing surface on the crank (3.1858). It's on the low end of the recommended tolerance of 3.188 +/- .003 for the one and two piece seals. He recommended a light polish of the serrations on the crank and trimming the two piece down to get a .020 preload to make up for being on the low end. Being at the low end of the tolerance doesn't give me a lot of confidence but I'll give it a shot. He also said the tip test isn't a 100% reliable way to check for leaks since some oil may seep past the crank serrations.

On the plus side, I got my carb back from Ray Klemm yesterday. Nothing fancy in terms of restoration or plating, just a rebuild and a tune. I'm really impressed that he runs and tunes the carbs before sending them off! He ended up putting a 72/39 combo in it. Can't wait to see how it runs, but I've got a ways before I mount the carb on top of this thing.

[Formulajones]

Originally Posted by Verdoro 68

He recommended a light polish of the serrations on the crank and trimming the two piece down to get a .020 preload to make up for being on the low end. Being at the low end of the tolerance doesn't give me a lot of confidence but I'll give it a shot. He also said the tip test isn't a 100% reliable way to check for leaks since some oil may seep past the crank serrations.

.

That's how I do them, and use the 2 piece, never an issue. I never do the tip test either

[HWYSTR455]

Yeah I thought the questions regarding the hash on the crank was brought up before? I too thought this was an aftermarket crank.

Just to say, applying sealant to the block/cap mating surfaces is a no-no, it should be dry & clean. It won't leak there ever. (and can contaminate the bearing surfaces and/or cause torque reading problems.)

The only time you see leaks there is from the seal parting line.

If you don't believe me, call BOP and ask.


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[Formulajones]

The same guys that tell you a vacuum advance isn't necessary, lol.

I don't care what BOP says, it will absolutely leak past the cap mating surface.
The gasket only goes over the top, and the rear main seal only seals the crank surface. The cap area is metal to metal and it will seep oil through there over time.

Where people make a mistake is applying a glob of sealant there. Of course that can cause bearing clearance variances and obviously if too much is used it gets into places you don't want. All you need on that surface is a very small line of green loctite. It seals and doesn't affect how the cap mates to the block, won't affect bearing clearance or torque readings. Done.

[HWYSTR455]

I say vacuum advance isn't necessary? Not sure if that was to me, but I've always said full manifold vacuum is the way to go.

Yes, metal to metal, and no, it won't leak. It's a machined surface torqued at 120, there's no seepage unless it's not machined right.

Ask Butler then if BOP, who makes the seal, isn't trusted.

https://www.bopengineering.com/seal_instructions.pdf

Just going to have to disagree on this one, please don't take it personally.

.

[Verdoro 68]

Via Butler:

We like the BOP two piece seal. Just need to make sure to follow the install instructions to make sure it’s installed properly. That’s the issue we’ve seen is people not following the instructions and having a leak.

Where the two seals come together you can add a little sealant to help with sealing. Also rotating them just little off from the parting line helps. Basically pushing one end just below the surface of the block while the other will be out of the block. The piece in the main cap rotated to match the block piece helps with sealing.

Interesting that they say to rotate the parting lines. I was reading a Buick site where they were using the seal and said the same. BOP instructions say you can do that, but they haven't found it necessary.

The BOP instructions say to "apply a thin film of silicone or anerobic sealer between the cap & block and anti-rotation holes only."

[Formulajones]

Originally Posted by Verdoro 68

Via Butler:



Interesting that they say to rotate the parting lines. I was reading a Buick site where they were using the seal and said the same. BOP instructions say you can do that, but they haven't found it necessary.

The BOP instructions say to "apply a thin film of silicone or anerobic sealer between the cap & block and anti-rotation holes only."

Yes the anaerobic sealer works for that too. Why BOP tells people on the phone to not seal the cap yet will send instructions along that say otherwise is puzzling. Makes me wonder if they've had customers that just went overboard with it, or used the wrong type of sealer and caused problems.

I don't rotate the seals here either, I just keep the parting line with the block and use sealant from the seal face out to the edge of the cap.
I've never found any advantage to rotating the seal. A parting line is a parting line.

Never had one leak.

[kingbuzzo]

gosh good work...not looking forward to giving this another go

[grandam1979]

We only fill rotation holes and on end of seal as recommended have had no issues. We have used 1 and 2 piece seals the one thing I can say is 2 piece so much easier to install. My engine has had a 2 piece in it since 2012 and has been run hard with no leaks. Crankcase pressure is going to make your engine leak faster than anything else except for a complete gasket failure. The last rear seal we saw leaking was a two piece but after a little investigation we found out the owner had removed the pan and rear cap in car and slipped it in It failed miserably.

[Verdoro 68]

The saga continues.

I misread his email and he said normally he'd recommend polishing the serrations, but since my crank is on the low end of the tolerance he didn't want to do that. Instead, he recommended I sand material from the end of the seal (rather than the radius) to get .020 preload, so I did.

I sent pics of the seal fitment to Wade and he said I was on the right track so I proceeded to button everything back up. I put a tiny smear of sealer under the rear main cap between the block and cap and a tiny dab on the ends of the seal. I ended up installing the seal seam with the cap/block rather than offsetting it.

After a 5 hours tilted on the stand, I've still got a slow drip off the back of the crank The pan seal and the cap to block are bone dry, so it must be the seal. The oil is collected on bottom of the flange of the crank hub like it was before. It's not a huge leak, maybe one or two drips over the course of the 5 hours, but I'd obviously prefer not to see any leaks.

I cleaned everything off really well and will keep it angled for a while longer with the hopes that what I saw was just residual oil, but I doubt it. I know some folks have had some drips via the tip test only to have it seal up once it's running and in the car, so I'm wondering if I just roll with it and hope for the best. Frustrating.

[HWYSTR455]

It's true, have seen it before as well, tip or other tests it may leak slightly, and once heat cycling a few times from running it doesn't leak in use.

I don't offset the parting lines of seal either, have never used the 1 piece.

I like the rope-type seals and have install of those down to an art. But those are not recommended with a crank that has no serrations.

.

[Verdoro 68]

Originally Posted by HWYSTR455

It's true, have seen it before as well, tip or other tests it may leak slightly, and once heat cycling a few times from running it doesn't leak in use.

I don't offset the parting lines of seal either, have never used the 1 piece.

It's definitely the seal. I folded a blue shop towel and wedged it between the crank flange and the rear main. Came back in about an hour and it had wicked some oil.

I checked the journal again with my dial bore and didn't pick up on it being out of round. My guess is this leak has to do with the crank diameter being at the bottom of the specs for the seal, or maybe it's just oil seeping past the serrations like Wade said. The only other thing I can think of is maybe it's getting past the anti-rotation holes? I filled them level to the cap as best I could.

Originally Posted by HWYSTR455

I like the rope-type seals and have install of those down to an art. But those are not recommended with a crank that has no serrations.

Not sure what to do here. Now is the time to make this as right as it's going to be. I have a graphite seal on hand but to confirm, those ARE NOT recommended for cranks with serrations, correct?

[Formulajones]

Oil will seep past the serrations when the engine is tipped. Generally you don't want to run those serrations with the BOP seals unless they are polished to some degree, so they don't eat at the seal over time. Those seals are designed for a smooth surface. The serrations are there for the rope seals, to keep them lubricated.

[Verdoro 68]

Do you all think I’m better off with the graphite seal in this case?

[tom s]

Im 50/50 with the 2 pc seal,100% with the one pc and 100% with the Best Gasket rope.FWIW,Tom

[AG]

Originally Posted by tom s

Im 50/50 with the 2 pc seal,100% with the one pc and 100% with the Best Gasket rope.FWIW,Tom

I'm 100 % with the BOP (stock and aftermarket cranks) and 100 % with the Best using a stock crank. The Best is better than the two-piece in the Fel-Pro sets.

[Verdoro 68]

I probably read too much and got my signals crossed. I thought the Best Gasket was best for a smooth crank. I saw some cases (like this thread) where the graphite seal got shredded and thought it was due to serrations. That's why I tried the two piece BOP this time around. On the whole, the graphite seals seem to be much less finicky and have a higher success rate. I don't have a problem pulling this thing back apart if it will work with my crank.

[HWYSTR455]

Agreed, there can be minor leakage past the hash marks even when everything is 'right'. I've noticed when engines sit parked for extended periods, this can become more evident.

I would have to go back thru my notes regarding if the Best rope seal is compatible with hash marks or not, all my memories at the moment are that I've always used the OE type ones that came with the Fel-Pro full engine gasket sets. Not the basic kit the 'premium' kits.

I would think a rope seal would work without hash marks as long as it has the graphite, but am not going commit to that at the moment. The hash marks were there to hold a touch of oil so the seal doesn't 'stick' to the crank when sitting for a period of time, or that's my understanding. (You can imagine, sticking is not a good thing). With that in mind, you can understand why the originals would weep a little right out of the factory, and might/can/is considered 'normal'.

If you understand that concept, you can clearly understand why there are 'anti-rotation holes' in the block/cap. When you pack a rope, pack hard in the areas of the hole, and concentrate on packing those areas first. You have to 'feed' the rope into those holes as you pack, accordion-ing the rope from the ends towards the holes. (If you can imagine that). Work from the parting lines to the center.

Also, I recall over the years the ropes included in those Fel-Pro kits went from an amber color to a more grey/black color, suspect that they started using graphite in them, not sure. I've had success with both though.

Packing the seal in the cap/block is a test of patience, crank has to be R&R'd multiple times to ensure you get the proper fit. It's a balance of drag and fit/clearance, but can say initially, there's more drag than one would think, required to make it seal right. After a number of heat cycles, it takes a 'set', and the drag loosens up some anyway.

Those 'custom' or intent-specific packing tools are garbage, using a large deep well socket (or similar item) to pack is what I've had most success with.

Ok, morning brain-dump completed, more coffee is needed...

.

[Verdoro 68]

Here's how much it leaked sitting on the stand at an angle overnight. I can see the dribble of oil from the bottom of the main on the crank flange. I don't think this is going to disappear if I run it this way.