dyno

OK I've had a day to sulk and contemplate.....heres what happened I built a new motor over the last few months bought parts off the board and through friends. I ran the motor on the floor for about 35-45 min. to look for leaks and break in the cam...no issues but it made alot of oil pressure 60lbs at and idle. put the thing in on Friday wrenched my a$$ off to get ready for the holiday. Well it rained most of the weekend so Monday was my first chance to sea trial
put it in idled around no leaks...put the boat on plane to get to the channel about a mile no leaks, cleared the channel headed south it was a little rough so I just made a big circle...pulled into the channel pulled back on the sticks and the oil pressure gauge bobbled and dropped from 60+ to less than 40...I hit the key cracked the hatch and the bilge was full of oil.....here we go again Took it to the shop cleaned up the mess and tryed to find the leak....it looks like the front seal...will that kind of pressure blow out a front seal?Wha6t the heck did I miss????the thing never leaked until it was in the boat not a drop when running on the floor so tonight I'll replace the seal and try again....I'm running out of energy to work on this thing...I leave on vacation this weekend may be leaving the boat home....

PatriYacht

If you have breathers, there isn't any pressure on the front seal. Unless it was torn from installation, I'd look somewhere else. On one of my old engines, the rear cam plug came out under pressure and dumped 4 quarts in about a half hour. Good luck finding it and getting out this weekend.

z.zuperboat

Mine Also Leaked From The Front.replaced The Seal Twice Still Leaked,sleeved The Damper.still Leaked.it Was The Timing Cover Itself.where The Lower Seal Goes Is Spotwelded On And Leaked There.the Cover Was New From Gm.this Is A Common Problem.removed The Cover Cleaned And Siliconed.still Dry To This Day.

dyno

Ian.... rear cam plug???? I re-filled and started it and dumped a qt in about 30 seconds....so ther is no pressure behind the timing cover??? the leak is definatley in the front.

88Fount33

I built a 406CI that had the mains line bored and honed, this required a very special rear main seal, designed for this enlarged bore, when assembled you could not see the gap between the seal and the crank, did not leak into the bilge until coming up on plane when the tilt of the engine put the oil against this seal in earnest. Five quarts to the bilge in 20 minutes, 0-PSIG at idle, switched off and towed to marina, bought 10 quarts to make it home, drove slow used all 10 to get there, all in the bilge by the time I made it back. I did not hurt the engine, but had to remove, tear down, and then wait for the custom sized Rear Main Seal to arrive. Once it was in (snaked it around the crank with out pulling crank). No more leaks. Still running 6 years later.

JUSTONCE

There is no measureable press. in the crankcase, but I had a motor that frt. mains kept leaking. I'd replace the seal and it would be pissin in a week. Well The problem was the fact I had used an aftermarket timing cover.(bad idea) The alignment holes drilled in it for the dowels were too big so even though the cover was tight And the new seals went over the crank they would wear out very quickly, distort and leak. Are you using one of those cheap chrome covers?

dyno

no a merc cover...

PatriYacht

A quart in 30 seconds?! It sounds like a leak in an oil gallery. Check your pipe plugs and sending units if they are at the front. I've seen front cover leaks but nothing like that. The timing chain is just oiled by splash. There is no pressure there.

PatriYacht

Do any of your oil hoses or oilcooler lines go neer the front? It has to be something under pressure.

dyno

I'm pretty sure its leaking from behind the balancer.....there is a place to plumb a temp guage in the front but that was the first thing I checked....and why didn't it leak during cam break in???it ran for over 1/2 an hour without leaking a drop.....isther a differance in timing covers? I used one I had laying around it cam off a marine engine but not sure if it was a gen 5 454 or a 502 I had a while back......