Back to fighting rear main leak

[505charger]

I have had the rear main seal out of my 505 stroker 3 times. The last with a red seal made for dry sump vacuum systems. Used the MRE retainer, sparingly used silicone sealer on sides and parting line, offset the seal halves a 1/4 inch into the block and you guessed it, leaks. This time has been the best so far. I'm down to drips instead of a gusher but still completely unacceptable on a new engine. I'm down to having a professional mechanic friend I trust install a rope seal? This seems stupid to me but what else is there to do? I have read all the past posts about bad factory machining and the controversy over using a rope seal. I just want a dry engine and willing to take the drag of a rope seal if it will work? I really don't want to pull the engine again. Help? Opinions?

[elacruze]

Me too.

I'm convinced (and suspected from day 1) that my ring seal is crap. I didn't disassemble the shortblock in mine, because it was near zero miles but the PO never drove it hard. Whatever few miles it had were mostly cold and on the choke, and when I ran it it didn't get right for 1500 miles. My main seal is good on long trips where manifold vacuum is high, but around town it pours oil like piss out of a boot. I've been too lazy to do a leakdown, and frankly I think I know already what it will say.

Perform a leakdown to see if you're generating crankcase pressure and pushing oil out the seal. Leakdown warm should be less than 10%, less than 5% is nice to see on a street motor.

[505charger]

It is a new engine as well. Maybe 100 miles total. I have noticed that there is some piston slap on cold starts which disappears with the engine coming to temp. I don't want to think it is blow by. I assembled the engine myself but all the machine work was done by a professional I have used and trusted in the past. The pistons are the KB Ichans. The crank was Chinese with American machining? I was told this was better and paid more for it. No chamfered rod bearings needed. I also have large breathers on my valve covers so even if I had blow by how could the crankcase get pressurized?
     Sooo, how do I perform a leak down? I have never done one.

[Cooter]

It is a new engine as well. Maybe 100 miles total.
     Sooo, how do I perform a leak down? I have never done one.

Requires special tool. Leakdown tester. Basically, looks like a set of dual guages and on one side is shop air press. On other side is what % of that air leaked down. So if shop air is say 100psi, and your other guage reads 50, then it has 50% leakdown.
Must back off rockers, or be one base circle of cam and piston at TDC. One cylinder at a time.
At least this how we do it for dailys..

[69wannabe]

 I got my rear main leak down to a minimum by installing a rope seal after pulling mine out 3 or 4 times. When I had the stock stroked 440 steel crank in there it was dry as a bone. Something not rite with these aftermarket stroker crankshafts. Mine would drip just while it was idiling, and it was a steady constant drip. I never tried to drive it that way. Finally got the rope seal in there and it still has a drip or two after I park it but not like it was before. It is fairly new so i'm hoping when it breaks in a lil bit it may seal off completely. Good luck with the dreaded big block rear main leak.

[505charger]

Thanks for your input about using the rope seal. I agree there must be something wrong with these stroker crankshafts that causes the problem in the first place. Anyone out there with the background to give an authoritative explanation why this would be? I have built 7 or 8 big blocks over the years and have never fought rear main leaks. Oil pan, valve covers, are the usual places. I would like to build another stroker motor and would like to know how to fix the problem during the initial build. Changing rear Main seals in the car is a PITA.

[Cooter]

I have only had one stock crank 440 give me problems with rear main.

I would be interested in the as well, as last night at Cruise night (605 Cars BTW!! new Record), a guy with a 500 Inch motor in a Duster was having problems with his Eagle stuff.

[69wannabe]

My kit had the eagle shaft in it too. I bought my rope seal from summit racing for an early 60's 413 which is the same as the 440. Its a fel-pro number and I will dig in my tool box and get the part number when I go out to the shop. I got a drawer full of part numbers for things that were hard to come up with.

[69wannabe]

The fel pro number is a BS11748. Can most likely be purchased or ordered from a reputable parts store. Have to pull the crank shaft back out of the engine to get it in there tho. When I put the rope seal into the block I positioned it with access seal sticking up from both ends and packed in in by hand first and cut off the access seal but not close to the block yet. Then I took a 3 inch 3/8 extension and rolled it back and forth packing the rope seal into the block tightly until it was in as far as it would go then trimmed the rope close to the block as possible. Did the same with the seal retainer and put a dap of black silicone at the seal ends and used some side seals from 440 source. Then back in with the engine. Nothing fun about it but I was desperate to make it better. 

[Challenger340]

I have assembled somewhere in the Neighborhood of 400 BB Mopars over the last 35 years....learned the hard way LOTS !!

I have posted my findings on this numerous times here on this Forum, so I guess one more time would Not hurt ?

The groove that holds the "upper" half of the main Seal in the Block on BB Mopars, 90% of the time, is NOT inline with the mains,
and also 90% of the time,
that OFFSET can be SEEN visually just looking at the upper SEAL half when sitting against the Crank in the Block, before the Seal Retainer goes on.
What you will see is the Crank compressing the Lip Seal on one side, and BARELY touching the Crank on the other side, which if not corrected during assembly will Piss Oil .
No amount, or number, of aftermarket Seal retainers will correct the "problem" 100%, Nor will simply offsetting the Seal itself 1/4"from the parting Line by itself on the worst Blocks.
Actually;
on the worst Blocks, the "stock" seal retainers work best, because they are sloppy enough side to side in the Block, which allows the Engine assembler, when using the seal offset 1/4" from the parting Lines, to drag the seal over on the offending(non contact) side slightly as you tighten the bolts.

IMO,
This CHECK..for Block Seal Groove mis-alignment...should be std practise on all BB Mopars and ANY Engine during Assembly...it is at my Shop...has been for over 25 years now.
What has baffled me over the same period....is the "explosion" of aftermarket BB Mopar Seal Retainers that hit the marketplace, which really do nothing to correct the real "problem".

To anybody reading this...next time you have a BB Mopar dis-assembled...have a "look" for yourself, and if you plan on re-assembling with a "lip" seal....try and remember this...it might save you a lot of grief later ??

[505charger]

Thank you for your response.I had been alerted to this misalignment of the seal in the block before I changed the last seal. I could not see any misalignment. I had the car on my lift and took a good hard look but it's not like having the motor on a stand! I am going to get other eyeballs on this when we try again.

[68Charger4me]

Thanks for the info Challenger, wish I would have known this when I assembled my 383 2 years ago, I'll be tearing out the engine to fix my rear seal leak too this winter.