this horse has been beat to death , but------

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famous bob

famous bob

mopar misfit
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I have had a rear mainseal leak since day one , I have finally found out why, after 3-4 times trying to fix it .
The main seal cap is not made right, or the bolt holes in the block are offset from perfect, or the crank is setting in the block crooked . Don't think it the crank cause all pistons were exactly the same deck heigth when built , if crank was crooked one side would be off , compared to the other side. I installed the main cap after cleaning it up w/o the side seals , letting it center itself on the crank , ( no bolts) , one side of the cap is way closer to the block than the other side . I redrilled the bolt holes out bigger and checked the bolts , they (allen heads) were .005 bigger than stock , slightly adding to the problem.
I still haven't figured out how to seal the cap on the sides , w/ the engine in the car ,
getting the whole mess clean of all oil would be a ***** , not to mention how to get sillicone up in there to seal it from the outside.
I have found a billet main cap that is offered by an old funny car racer, and not like the current ones on the market, ordered it this morning. If its the same way , sealing the sides will be a bithch , 73 yrs old and laying on a piece of cardboard in the floor aint fun any more !

Sorry for the long rant m "more to come !"
 
famous bob said:
I have had a rear mainseal leak since day one , I have finally found out why, after 3-4 times trying to fix it .
The main seal cap is not made right, or the bolt holes in the block are offset from perfect, or the crank is setting in the block crooked . Don't think it the crank cause all pistons were exactly the same deck heigth when built , if crank was crooked one side would be off , compared to the other side. I installed the main cap after cleaning it up w/o the side seals , letting it center itself on the crank , ( no bolts) , one side of the cap is way closer to the block than the other side . I redrilled the bolt holes out bigger and checked the bolts , they (allen heads) were .005 bigger than stock , slightly adding to the problem.
I still haven't figured out how to seal the cap on the sides , w/ the engine in the car ,
getting the whole mess clean of all oil would be a ***** , not to mention how to get sillicone up in there to seal it from the outside.
I have found a billet main cap that is offered by an old funny car racer, and not like the current ones on the market, ordered it this morning. If its the same way , sealing the sides will be a bithch , 73 yrs old and laying on a piece of cardboard in the floor aint fun any more !

Sorry for the long rant m "more to come !"
Click to expand...

If you replace the main cap, it has to be remachined to match your engine - align bored... You will have to pull the engine out and strip it down to the block to get it machined... When they machine a block, they rough bore the caps and mains, then bolt them together and align bore the crank bores so they are all lined up properly - that's why you can't mix and match the caps and have to keep them in the proper order that they were machined on the block....
 
Donnie514 said:
OK, this is a big block...right?
Click to expand...

Oh yeah, big blocks have that funny rear seal, not like the small block....

You may not have to get it machined if it's a big block... I'm more familiar with small blocks...
 
Somebody makes a rear seal retainer to address this.
 
toolmanmike said:
Somebody makes a rear seal retainer to address this.
Click to expand...

Not sure but think this may be what you are referencing:

Mancini Racing Billet Rear Main Seal Retainer

"Fits: Big Block, Mopar

Billet aluminum rear main retainer. It uses double o-ring on each end to seal the cap to the block. This retainer is designed to hold the proper diameter to clamp the rear main seal properly.

Sold in kit form with Cap, 4-O-ring seals, Rear main seal, 2 - alignment pins for easy installation and socket head bolts"

mancini-racing-billet-rear-main-seal-retainer-31.gif
 
famous bob said:
I have had a rear mainseal leak since day one , I have finally found out why, after 3-4 times trying to fix it .
The main seal cap is not made right, or the bolt holes in the block are offset from perfect, or the crank is setting in the block crooked . Don't think it the crank cause all pistons were exactly the same deck heigth when built , if crank was crooked one side would be off , compared to the other side. I installed the main cap after cleaning it up w/o the side seals , letting it center itself on the crank , ( no bolts) , one side of the cap is way closer to the block than the other side . I redrilled the bolt holes out bigger and checked the bolts , they (allen heads) were .005 bigger than stock , slightly adding to the problem.
I still haven't figured out how to seal the cap on the sides , w/ the engine in the car ,
getting the whole mess clean of all oil would be a ***** , not to mention how to get sillicone up in there to seal it from the outside.
I have found a billet main cap that is offered by an old funny car racer, and not like the current ones on the market, ordered it this morning. If its the same way , sealing the sides will be a bithch , 73 yrs old and laying on a piece of cardboard in the floor aint fun any more !

Sorry for the long rant m "more to come !"
Click to expand...


Have to agree. Although didnt verify your
Observations.
I built this B block back in 1992.
383 .60 over nothing fancy 11:1 open chamber ported heads.Gear drive.
This thing leaked from day one. Interesting.
Mainly after 30 minute drive or so.
Nitrous playtime sure didnt help.
But engine strong.

I didnt want to think something I did or didnt do....
 
Confucius say, It ain't a MOPAR if it don't leak !:lol:
 
fklskv said:
I used the Fast Fish seal and retainer. Did it with the engine in the car. No leak since

Performance-Engine-Seals
Click to expand...


The engine came out of as 66 Chrysler still mated to the trans, it had a rear main leak when I tore it down, which I didnt pay much attention to because I was not going to use anything but the block. Anyway, I have found that the cast rear maim seal cap is .061 shifted to the pass side , . Waiting on new one --------
 
famous bob said:
The engine came out of as 66 Chrysler still mated to the trans, it had a rear main leak when I tore it down, which I didnt pay much attention to because I was not going to use anything but the block. Anyway, I have found that the cast rear maim seal cap is .061 shifted to the pass side , . Waiting on new one --------
Click to expand...
Interesting.
My 383 was out of 67 New Yorker....
 
mycuda said:
Interesting.
My 383 was out of 67 New Yorker....
Click to expand...
My deck height only had to have .003 taken off to be perfect , I think the machine work on the early blocks might have been real close . ??????????
Cast main seal cap , not so much.
 
famous bob said:
My deck height only had to have .003 taken off to be perfect , I think the machine work on the early blocks might have been real close . ??????????
Cast main seal cap , not so much.
Click to expand...
I always heard the Chrysler engines were carefully assembled. More like they were factory blueprinted.
 
toolmanmike said:
I always heard the Chrysler engines were carefully assembled. More like they were factory blueprinted.
Click to expand...

I know they have been way closer to perfect than any of the chevy blocks I`ve messed with, they have been off a mile from what the factory said.
The two 426 hemi`s I had were spot on perfect !!
 
MOPAR4Me said:
Found another very interesting read over at moparts.

440 Rear Main Seal Leak--Almost Suicidal!! UPDATE

Excellent points and primary solution appears to have been provided on the first page by poster, Monte_Smith https://board.moparts.org/ubbthread...al-leak-almost-suicidal-long.html#Post1851803

But the read leading up to that and after is great. https://board.moparts.org/ubbthread...ar-main-seal-leak-almost-suicidal-update.html

Good luck.
Click to expand...

Yeah that would be me, I haven't had another big Mopar leak since. J.Rob
 
famous bob said:
The engine came out of as 66 Chrysler still mated to the trans, it had a rear main leak when I tore it down, which I didnt pay much attention to because I was not going to use anything but the block. Anyway, I have found that the cast rear maim seal cap is .061 shifted to the pass side , . Waiting on new one --------
Click to expand...

May have missed it, but aside from the cast rear main seal cap shift issue, is your install past/planned also including the seal position rotation offsetting in relation to the seal retainer/block flange mounting area?

159691-bfb45d4a15918da7faa7f55425bf5326.jpg
 
Last edited:
I built one years ago. 3-4 rear main seals later, found out it was a marine engine reverse rotation. Pulling oil out of engine.
 
w2dart said:
I built one years ago. 3-4 rear main seals later, found out it was a marine engine reverse rotation. Pulling oil out of engine.
Click to expand...

Well I haven`t got the pan back on yet , but the new seal cap came in yesterday , and is the neatest I`ve ever seen. CNC`d and fit like a glove, couldn`t have been any more perfect, centered the maim seal , fit the side of the block perfect and tite both sides.
I was kinda worried about the side rails tho , as tite as it fit the block . I got the bright idea of glueing the soft rubber side rails to the cap , using DAP fusion weld, a fast setting , glue anything ''but pure silicone'' , glue.
Held it on a flat surface for about 15-20 seconds in position while setting up, oiled the sides of the rails when installing, had to apply a little push in pressure on one side to get started, went in w/ a good amount of pressure to install, when it hit the circular part around the crank , I had offset about 3/8" , I could tell it pushed them together to mate, really happy w/ it ---------reworked the funny car windage tray to fit the reworked funny car pan , will install it today. Mwuay old *** wore out -----------more to come.
 
oldkimmer said:
Glad to hear everything is working out. Kim
Click to expand...

PUT THE PAN AND WINDAGE TRAY ON TODAY, GOT THE RACK AND PINION BACK IN , JUST NEED TO GET A GOOD FILTER AND ADD OIL NOW. CAN EVEN RUN A REGULAR FILTER NOW AFTER REWORKING THE FAN SHROUD , HAVE HAD TO RUN A SHORT FILTER UP TO NOW.
I DID CHUCK THE FRONT MAIN STUDS UP IN MY LITTLE LATHE AND SHORTEN THEM, I CAN GET THE PAN OFF NOW W/O TAKING THE RACK AND PINION /STEERRING STUFF LOOSE .
 
famous bob said:
PUT THE PAN AND WINDAGE TRAY ON TODAY, GOT THE RACK AND PINION BACK IN , JUST NEED TO GET A GOOD FILTER AND ADD OIL NOW. CAN EVEN RUN A REGULAR FILTER NOW AFTER REWORKING THE FAN SHROUD , HAVE HAD TO RUN A SHORT FILTER UP TO NOW.
I DID CHUCK THE FRONT MAIN STUDS UP IN MY LITTLE LATHE AND SHORTEN THEM, I CAN GET THE PAN OFF NOW W/O TAKING THE RACK AND PINION /STEERRING STUFF LOOSE .
Click to expand...

update/ got around to driving it yesterday, no leaks ! I highly recommend junking the stock main seal cap and buying a cnc`d billet one . About anybodies will probly work.
First time I haven`t had a leak on this 52 yr old barracuda !!---------fingurs crossed !
 
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