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Thread: Oil Leak on SBC....please help.

  1. #1

    Oil Leak on SBC....please help.

    Hello. We just bought a brand new 406 from Shafiroff and we are having problems with an oil leak. The first time we started the motor, it looked like the oil was coming off of the oil pan gasket in the rear of the motor under the crank. So we then dropped the pan, cleaned everything up and gooped it up with a sealer and bolted it back up. Well.....we tried it again last night and it still leaks. The problem is that it still looks like the leak is coming off of the oil pan but it is so hard to tell. We know that there is a possibility of it being the rear main seal, but it just doesn't look like it. If we look at the end of the crank, flywheel, and converter....there isn't any oil on any of them!!!??? If it was the rear main seal wouldn't the oil be all over the crank and flywheel????!! When we start the takes about 15 seconds of it running and then the oil starts dribbling down the back of the oil pan. Please....if you have any suggestions or have experienced the same problem plase let me know. Thank you, Derek.

  2. #2
    Senior Member EXPERT BUILDER
    Join Date
    Aug 2005
    Tell City, IN
    It isn't coming down from your oil fitting is it? I have even seen valvecovers leak in the back and run down the back of the motor down the pan. Just some idea's.

  3. #3
    Senior Member MASTER BUILDER
    Join Date
    Apr 2006
    Also look at the rear of the intake,(where the intake meets the block) they are bad to leak there and it would run down the back of the block.

  4. #4
    Senior Member RACING JUNKIE
    Join Date
    Feb 2004
    san antonio, texas
    if its brand new you should call the dealer back and should not have
    opened it up, now they can say you made the leak, you would be amazed
    at the trail an oil leak can come from, your dealer should be notified :?

  5. #5
    Senior Member RACING JUNKIE
    Join Date
    May 2003
    Coldwater, MI
    Quote Originally Posted by signsbyesa
    if its brand new you should call the dealer back and should not have
    opened it up, now they can say you made the leak, you would be amazed
    at the trail an oil leak can come from, your dealer should be notified :?
    With my dealings from the place he got it he was SOL no matter if it went to 1000 parts on the garage floor.

    My sb from them leaked like a son of a gun I put a 1 peiece fel-pro gasket on it that helped some the leak but ended up being the rear main seal. When changing it.. make sure the parts you paid for are in the motor just my past dealings with them.
    David Lanning
    IHRA NHRA 387B

    Fleenor Racing Transmission
    Lanning Electric
    Complete Drag Car Wiring
    APD Race Engines

  6. #6


    try this first take a can of cheap primer paint and spray back of pan and up back of block , let dry then start motor and then you will see where its comming from, i have seen people put the seal on the rear main in backwards and thought it was the pan, this paint trick has help freinds of mine to find leaks, good luck..

  7. #7
    Senior Member RACING JUNKIE mopar1968's Avatar
    Join Date
    Dec 2006
    either rear of intake or dist seal
    Head's up the true drag race!!

  8. #8
    Thanks for everybodys input. Needless to say we still haven't completely stopped the leak. We took the motor out last night, cleaned everything up. We have a shaft with a drill we use to get the oil primed which build oil pressure. So we did this and watched the back of the block for leaks. We found that there are three 1/4 set screws about where the camshaft is. Two of these were flush with the block, and one was sticking outwards about 1/8 inch. The one that was sticking out leaked oil when we ran the oil pump. So we then taped it and put a little sealer on it and put it all back together. We then started the car and let it run for about 15 minutes (Temp of 180). It didn't leak at first, but then the oil started thinning and it started to leak a bit in the same place as the night before. The only good thing that came out of this was that it only leaked about 6 drips while it was running, and the other night is leaked a puddle on the ground. So now we really don't know what we should do. Obviously we need to take it back out and try something. We thought about tapping the hole a little deeper, but then we have to worry about getting metal shavings in our oil. Has anyone else had any problems with these set plugs??? We have pretty much ruled out the rear main seal, because there isn't a drip of oil on the crankshaft or around the seal. It runs down from that plug and down around the crank and down the motor plate/oil pan. If you have any suggestions please let me know Also, this is a Dart 'Little M' block. Thank you, Derek.

  9. #9
    Senior Member RACING JUNKIE fla1976's Avatar
    Join Date
    Aug 2007


    I would suspect the other two allens at the rear of the block near the cam. If one was loose, the others may not have been sealed correctly too. Does it have oil restrictors? Would also check at the cam plug (freeze plug) and see if it is leaking there. My 377 would leak at the intake manifold where it meets the block near the distributor. The problem turned out to be the manifold was poorly machined at some time, would leak at the strangest times. Used gasket in a tube to seal it.

  10. #10
    Senior Member RACING JUNKIE
    Join Date
    Jul 2007
    Independence, Missouri
    Make sure that the plug and hole are not threaded with different threads. ie NPT & SAE.

    No matter where you go, there you are.

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