Spridget- Engine Rear Main Seal kit- Mini-Mania ?

J

Joel McGinley

Well-known member
I have a Street 948cc Bugeye that I put in the garage about 12 years ago. I am now reviving it, including an engine rebuild... One of the big problems was rear main seal oil leakage, so about that time I bought a kit from Mini-Mania in California- this installs a lipped rubber oil seal to the rear main, which runs on the crank flange OD. Does anyone have experience with this kit? Is it worth the effort to install it? Is the seal itself still available, since mine will be 10 years old in-the-box... ??? Joel
 
Save your effort - these kits rarely work. And if they do initially slow the leak, they soon lose their effectiveness as the crank flange wears out the seal. Better to add a PCV system - that's what reduced my street 1275 BE from a big dripper to a manageable, relatively dry motor.
 
Same experience here. Sometimes just properly venting the crankcase will stop the oil leak and other times you have to get a little negative pressure in the crankcase. If you have the mechanical fuel pump opening in your block you can just tap the cover plate for a fitting and use that opening for a vent hose or your PCV hose.
 
Here's how I was able to 100% fix rear main oil seal leaks:

* install main bearings, crank, thrust bearings, caps, torque to spec
* locate any half moon shaped rear seal plate (3 bolt holes) that is not goobered up near main journal
* grind a small chamfer on the seal surface so you can easily pry it off the block on it's located with roll pins
* carefull dress the back of the seal plate and block with a stone or file to remove all burrs, chamfer plate if needed
* stamp a number or mark (centerpuch) of some unique kind on both the block and plate near one another but not on the gasket face
* install paper gasket, plate (shoving it toward the crank till it actually touches), 3 bolts, torque
* if touching makes you nervous use a .001" piece of shim stock to space it away from the crank
* turn assembly on end so that rear of crank points up....put it on a drill press
* using a 1/16" diameter drill bit drill 2 holes (1R, 1L) on the opposite flats such that you still have socket clearance for the 7/16" hex.....dont worry there is plenty of room for this. drill through the plate and into the block about 1/4"
* purchase 2 1/16" diameter X 1/2" long spring roll pins from Home Depot or bearing supply house
* carefully hammer/push both pins in holes until flush
* disassemble, deburr using a 3/8" drill bit, clean as needed
* leave out the crank and bearings but install the main caps, half moon cap, torque
* have block align honed........not align bored....BIG difference

Messy.........but this method will solve your rear main leak problems. Crankcase venting helps but I ran a drysump in my H car so I never needed a vent.
 
Hmm, seems there is agreement about Jay's approach, but is there a way to create a positive crankcase ventilation system that will lower the pressure in the engine and reduce leaks? I have seen street cars with some sort of check valve that connected to the exhaust- I think it allowed suction pulses to pull engine vent gasses into the exhaust? Or other ideas? I'd even wondered about using a small DC fan to suck on the vent hoses, through a catch can/filter to reduce blowby pressure but let the oil droplets be captured???? Still have time to decide what to do... Joel
 
Joel McGinley":3gw4lnh6 said:
Hmm, seems there is agreement about Jay's approach, but is there a way to create a positive crankcase ventilation system that will lower the pressure in the engine and reduce leaks? I have seen street cars with some sort of check valve that connected to the exhaust- I think it allowed suction pulses to pull engine vent gasses into the exhaust? Or other ideas? I'd even wondered about using a small DC fan to suck on the vent hoses, through a catch can/filter to reduce blowby pressure but let the oil droplets be captured???? Still have time to decide what to do... Joel
Click to expand...

I have posted this info a couple other times. You can not connect the breather to the exhaust other then that breathers are open even for Prep 2. There are a couple different options to create a crank case vacuum.

You can use an electric vacuum pump but need to add an air/oil separator but because the electric ones can not handle oil in the air.

I have also been looking into the use of an electric pump which were used on Chevy's and BMW's. I don't think they pull that high of vacuum on the V8's to see HP gains but may work for our smaller motors.

Here is setups and info on these pumps.
http://forums.corvetteforum.com/c4-forc ... works.html
http://www.turbobuick.com/forums/genera ... p-how.html
http://www.t6p.com/forums/showthread.php?t=12995

Here is another option but I am not sure if the batteries will last for the entire race.

http://www.starvacuumpumps.com/products/STR.04.06.000

For the air/oil separator you could use some from the hardware store or one of the better ones I have seen lately is the MANN ProVent 200 or 300 depending on the size or you engine.

There are also belt driven vacuum pumps.

http://www.moroso.com/catalog/categoryd ... code=17200

Here is a smaller pump that I have looked at:
http://www.starvacuumpumps.com/products/STR.09.04.000

Peterson also makes a external wet sump oil pump and vacuum pump all in one called the Wide-VAC.
http://www.petersonfluidsys.com/pump_wet.html

You will need to add a vacuum regulator to the system so you don't pull too much vacuum. You need to make sure you have a good oiling system because you reduce the oil mist in the crank case and this can cause problems with the piston pins.
 
Joel,
I've used Minimania rear seal kits on both motors successfully. Installation isn't as hard as disassembly, but still doable. You do pull a negative pressure, but the proper insertion of the seal needs to block internal pressure from pushing oil out the rear, so you don't get much pressure drop.
 
A couple of comments - Jays description is missing a couple of details I think: You have to have the third main cap removed in order for the half moon shaped seal plate to be able to contact or even come close to the crank. Otherwise the mating surfaces of the main cap and seal plate will define where the seal plate mounts, and it will be the same as it was before. Then when the new location of the seal plate has been defined the amount that it sticks proud to the block must be removed or else the main bearing cap will not seat correctly.

Glad to hear that Harold had some success with the MiniMania seal kit, and that was really the first time I had ever heard of anyone having some luck with those kits, but it should be pointed out that Harold has a dry sump on a 1275 race motor, and the original question was how to seal a 948 street motor, so there will be some variation in mileage on that one for sure. I know that the seal kit that we tried on our 948 race motor did NOT work and we stopped using it.

On a new block that is being line bored (not honed), make sure that you machine the mounting surface of the seal plate so that it gets line bored along with the main bearing.
 
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