I have never had any luck with rear main seals in the 15 years that I have been working on these motors.They always leak eventually either a little or a lot!This one is a Mega block that I usually take out every year and try sealer here,sealer there,mill the holder a few thou,neoprene seals,rope seals etc.Has anyone had luck with these Mancini billet rear mains when everything else has failed or will I just be wasting my money?
Thanks Mike

is it a world block? if it is, maybe it's not the seal. i had a bad block. groove in the block was machined too wide & was off center to the crank.

It is an older(6 years) MP Mega block.
Thanks Mike

Mike
I used one in a older mega block Hemi. It worked for that one.
But it is hit and miss. I do think its a better design.

Jim

No experience, yet, because I just installed one in the 440 I'm putting back together. It certainly looks like a better design, but don't forget to check if you need to grind the seal holder for clearance if the rear main cap studs or nuts are keeping it from sealing properly against the block. I had to a bit on mine because it was hanging up there a bit.

I've got one on my older MP siamese bore block. I've had it out and back in 3 times and never because of a leak, It's worked great for me. Hemi Ram on the board has one in his World block and had problems with it leaking. It turned out he had ARP main studs and nuts. The 2 back studs hit the seal holder holding up from seating completely. A little grinding on the seal holder is all it would have taken.Dave

I build a lot of Chrysler B motors. Through much aggravation, here is what I discovered about the BBM rear seal..


-I ONLY use the reddish brown colored Fel Pro "fluoroelastomer" seal. It cost around 30 bucks so its not cheap, but I dont waver here.

-The premium cranks with the smooth RMS surface I never run into a problem. The Chinese cranks with the knurling on the RMS surface has given me some problems. Some of these have very aggressive knurling that, I believe, tears up the rms lip. I always send those cranks to the crank guy for checking and correcting anyway and we usually take .006 off the surface of the RMS area. That makes it smoother and knocks down the high spots. A rope seal would peobably work in this case with no mods-but I dont want to deal with that.

-The new billet RMS retainers are nice, but I found one flaw. If you look at the piece when its installed, it seems to "shroud" the area around the rearmost main cap. While this is only a theory on my part, I think the oil(especially when cold) can build up back there and not adequately drain. To correct this I mill a slot about 1.5" wide to give some room for better drainage. Its no big deal. If you want to see a cap that I think is done right, its the one that Best Machine sells. Its anodized red in color and has the relief that I mentioned already in place.

Ill see if I can post up some pics later. Nothing ruins a nice engine build more than a friggin rear main seal leak...

MB

Not a hemi, but I had a terrible time with my 512 stroker. I replaced the seal 3 times with the stock seal holder. Everyone would hold for a week or two, and then leak. I finally put the billet holder in, and so far, everything is nice and dry. I had never had a seal problem before this motor.

Another important thing to note is seal alignment. A factory rope seal has the benifit to a large contact area and is not citical to seal retainer alignment. The aftermarket neoprean and flouroelastomer seals only have a small knife-edge contact to the crang. Any missalignment from upper to lower half can cause leaks. The only two ways to garranty no leaks is to align the seal retainer using both seals installed in block and cap but without crank installed then scribe a mark to indicate alignment, or the crank is already installed stagger the halfs so that it will garranty alighment.
Allan G.

"A factory rope seal has the benifit to a large contact area and is not citical to seal retainer alignment. "
This is a 4.5 Callies crank!
Wonder if I should just try a rope seal with my original Mega block seal holder before I fork out the $70 for a hit or miss chance???
Has anyone tried this?
Thanks Mike

Caution - The rope seal needs a crank knurl to work. You would burn the rope seal without it.

Allan G.

I have used the factory cast units for years then I bought a few of them from Muscle Motors they both worked perfectly
The one in my engine is dry and I also used one in a street engine I built for another member here with no complaints so far
I had to trim mine for the studs but with ARP bolts it fits tight
Gus

GOOD POINT about the overly-aggressive knurling of the RMS area on some of the aftermarket cranks. I read this earlier and called a bud that is putting together a 4.15 crank motor. He said it appears somewhat over-board ... can you just use a strip of 120 paper on it ?

I bought my retainer and seal from Hughes for this eng in the car and so far zero leaks. Ron

I guess I will give it a shot on one of these Billet retainers since I will not be able to try the rope seal with my Callies crank.
Thanks All
Mike

https://board.moparts.org/ubbthreads/show...rue#Post7391808

Here is what I have done and so far for me it has worked well.

I WISH I had the true answer to why these are such a pain....It seems like everybody that has a problem is using aftermarket cranks so I believe the problem starts there.

Best Machine is currently out of stock of the modified Billet rear mains and do not know when they will have any more
I guess I will order one from Mancini and modify it to be like the Best Machine one. Anyone have any photo's of the Best Machine one?
Thanks Mike