More questions of fixing a rear main oil leak

[AL in NY]

Can't seem to get the rear main seal to stop leaking. I have a pressurized oil system that is pressure limited to 35 PSI. The main and rod bearings are inserts (block machining done by Rich Fallucca). The main bearing clearances were checked and found to be .0015 inches. Crankshaft end play is less then .004 inches. Schwalms did the countered weighted crankshaft and machined the slicker to the 2.090-2.100 dimension for the 2 piece cork/neoprene seal. The rear main oil return pipe is clear and not installed too far into the cap. I have tried twice to install the 2 piece cork/neoprene seal without success. The first time I installed it incorrectly by trimming it. Last month I installed it again (correctly I believe) and pressure tested it at 10 PSI and saw no leaks. I installed the engine and did the correct(according to directions) break in for the seal and saw no leaks. No leaks first the first 100 miles, but now it is leaking again. My first question: Is there some trick to installing this seal to keep it from leaking? I did think about installing the one piece Burtz seal, but my crank slicker is at the lower end of the size spec for using that seal, so I used the 2 piece seal again. Second question: Which seal would be better at sealing the rear main when using pressurization, the Burtz one piece seal (with my 2.100 size slicker) or the 2 piece cork/neoprene seal? Last question: Can high engine revolutions (3000 rpms) distort the seal during early break in operation, causing a leak? I'm getting very frustrated trying to get the rear seal to stop leaking. The engine runs perfect, it just leaves an 8 inch spot of oil anytime a stop. THANKS IN ADVANCE.

[Richard in Anaheim CA]

Al,

I think your best source is your two machinists and the seal manufacturer. I have run two pressurized engines for years. They both have Burtz seals. They have been replaced and engines rebuilt and they leak.

I think the wages of sin (pressurized oil system) is leakage and we are doomed to the diaper or the oil collection pan.

I live with it for the comfort of watching that oil pressure guage as I travel the vast stretches of our beautiful country.

Richard
Anaheim CA

[BRENT in 10-uh-C]

Are you certain the oil is coming from around the crank journal and not up the bolts? Second, I read where you say your crank slinger is at the lower limits. I would think to run a cork seal, the slinger better not be there at all. Otherwise the slinger would be rubbing the seal and prematurely wearing it out.

I guess now my position would be that if you said you tested it to PSI before with no leaks, then pull it back out and re-pressure test it to determine exactly where it is leaking.

[spinelll]

Originally Posted by AL in NY

I have a pressurized oil system that is pressure limited to 35 PSI. .

How do/did you pressure limit?

[AL in NY]

Brent, when I said the slicker was at the bottom of the spec limit to use the Butz seal I was referring to the area of the crank where the slicker used to be. It's diameter is 2.090 inches. The specs for the 2 piece cork/neoprene seal is 2.090 - 2.100 inches. The specs for the Butz seal is 2.090 - 2.150 inches.

spinelll, I am using a brass pop-safety valve in 1/4" MPT set to 35 PSI. I purchased it at McMaster-Carr. The part number is 9889K107. I modified it and removed the test ring on the top of the valve. Cost was $21.92 with shipping.

[1931 flamingo]

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Why not drop your pressure to the 10 lbs where you say you had NO leaks?? 10 lbs is still a lot more than an A w/out a pressurised system.

Paul in CT

[AL in NY]

1931 flamingo, I used 10 PSI to test the seal before installation. I added oil down the rear main return pipe and then pressurized the return pipe with 10 PSI of air pressure. That seal shouldn't see 10 PSI with the motor running and the return pipe open to the crankcase. I ran the motor for 100 miles with 35 PSI of oil pressure before it starting leaking. I was asking if anyone could tell me why the seal failed when initially it was good.

[Kurt in NJ]

Have you checked the seal surface for runout and roughness---if the seal surface was cut on a different centerline and it moves the seal enough that it bounces it can become a pump instead of a seal ---a new seal can be compliant and tight enough at first to not leak, if the seal surface is rough it will chew some off the seal--wear it out quick.

[spinelll]

Al

Thanks for the follow-up.
Where did you install the valve?
I have a pressurized system and at times the gauge registers way up there.

[AL in NY]

spinelll, I put the pressure regulator valve in the valve chamber along with the other plumbing.

Kurt in NJ, a had the cranksahft done at Schwalm's and I don't have any way to check for a off-centered seal surface, so I have to assume it's correct. The seal surface itself was as smooth as the main and rod journals, so I don't think that's the cause of the leak either.

[DaveB]

Al ... I hope you find the answer since I have exactly the same problem on a B engine. I followed all the directions and was very careful about the installation. No leaks for several hours on the test stand .... but it started before we put it in a car.

I am not sure what we have to do to change the seal to the Chevy two piece seal, but those seals were used for years and even by several Model A builders and never seem to have any serious leaks.

[Duffy1]

I am new to the model A world so please for give me if this is a dumb question . Why do so many folks want to modify the original design . Right after I bought my 31 sw with B engine it developed a major oil leak out the rear main . Pulled the engine and discovered that the fellow that rebuilt the engine had put a chevy rope seal in the space between the slinger and the edge of the rear main cap . The rope seal had come apart in small pieces and the pieces had plugged the return oil passages . Thank goodness the rebuilder left the slinger in tact . Cleaned out all the pieces from the oil passages and put it all back together . NO LEAK .

[abennett]

Al
I have had the same problem as you. B engine using the cork/neoprene seal, no leaks. I pulled all the bearing caps to check clearances when doing some other engine work and installed same seal since it still looked good. Installed engine, oil leaked. Pulled engine, seal was leaking where the 2 haves meet, fixed that, installed engine, oil leaked. Pulled engine, pressure checked as you did through the oil return pipe, oil was leaking around crank as the seal was not seating tight enough around crank. I then shimmed the seal for a tighter fit and pressure checked, no leak. Installed engine, after 75 miles oil was leaking BAD. Pulled engine, (getting good at pulling engine HA!) I had tightened the seal to much which then burned the seal. I have gone to the graphite rope seal from EGGE in Whittier, CA. part NO. 6382S, I am running 25 lbs. pressure and no leaks after approx. 200. I am a happy camper now. Wish you luck with yours.

[James Rogers]

Fellows, I believe I know where your leaks are coming from. If you look at the area where the aluminum seal goes into the block you will notice when it is in and the lip is in the groove in the block, the seal goes into the aluminum housing. Look at the ends of the seal where the groove is and you will see a small square hole because the aluminum seal lip does not completely seal this groove. This groove is in front of the cork seal and when the oil gets to full pressure it can force oil out these square holes if they are not sealed. I have even had original systems to leak from this area. This may not be the problem but it is as good a place to start as any. When I put in a cork seal I use grease to saturate the cork so it has plenty of lube for startup. I also make sure the aluminum seal is glued in with permatex #2 and force plenty into the little square holes. Since I have been doing this, I have had no leaks. I can try to post some pics tomorrow if I can find some or, the next motor I do.

Luck to all.

[AL in NY]

abennett - I just downloaded Egge's catalog and did a search on PN 6382S and it's a seal for a 68-69 Pontiac 428. What modifications did you do to repair the cork/neoprene seal with this seal?

james, I sealed that aluminum seal really well when I installed it, so I don't think the leak is there.

guys, thanks for all the responses. It looks like I am not the only modeler having problems getting this seal to work properly.

[abennett]

Al:
The seal is listed for Pontiac and is smaller than the cavity that the seal goes in. I fabricated a filler from 1/4" copper tubing to take up the space needed to make the seal a proper fit to the crankshaft. Give EGGE a call, they may have a seal now that is better fit. It has been some time since I got mine. I wished I had taken pictures of the spacer I made, but that is hindsight now. Any more questions, I'll try to answer.
Al Bennett

[James Rogers]

Al, here is the area I found to be a potential source of leaks at the rear main. Some people don't seal the aluminum seal with anything but, when they do it is usually just in the crease at the back of the cast and aluminum. In picture 2 you can see the 2 square holes I mentioned that do notgenerally get plugged. These holes are in front of the cork or Burtz seal and if the channel gets full plus has pressure, the oil can escape here. Even with the cap on, as in pic 3, you can see that these are an open channel to the flywheel housing. I always force a little permatex #2 down in these holes before installing the cap so as to plug this problem area. I do this on all my engines, babbitt and insert. Even the shims won't cover this area.

[AL in NY]

james, thanks for the photos of that potential leak area. On my engine build, I filled the cavity under the aluminum seal with LOTS of permatex "Ultra Black". It squirted out all over when I put the aluminum seal in. I assure you it's completely filled.

[columbiA]

Not leaking out the gasket between the block & FW hsg?

[AL in NY]

columbiA, No, it's at the rear seal !!