Thread: oil leak

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Well took my 37 out tonight since its the first nice weather weve had in two weeks. Cruising around 65 and pushed it up to 90 no problems. Got back home and open the hood up as it was ideling to fast and I saw that the passanger side of the engine was pretty well covered with oil. Spent the last hr.looking for the leak with both the engine off and running at high idle but couldn't fine the leak. Always had a very slow leak from the pan but this is from something else. Engine runs fine

Passenger side could be the gas pump plate or ever the gas pump loose.

350? That's an easy one.



IMPORTANT!!! This hole is drilled through to the fuel pump push rod. If you install too long of a bolt, it will bottom out against the fuel pump pushrod and possibly damage the rod if you try to start the engine. Just buy the shortest 3/8ths inch bolt ou can get and throw a flat washer under it (preferably copper).

It's a 305, same block but I haven't had this problem in over 4 years. Just started last night. At idle or even at 2 grand no problem but since I don't have a lift(guess I'll have to take it to a shop) and even thin me can't fit under it. Have ramps and I'll put those under the front and jacks under the back so the wheels are off and set my throttle for high speeds and see if I can find the leak. Not much back left to mess around under a car.

Is that bolt installed? Just try it. I had a mystery oil leak that would dust my headers with oil while going up hill at highway speeds only. It would make a big cloud of smoke. I'd go home and see a film of oil around the front passenger side of the engine. I could only get it to leak at high speed and high loads. It was very difficult to trace it down. I started replacing things. I did the timing cover gasket and front seal 3 times, the oil pan gasket once, and the fuel pump gasket once, then the whole fuel pump. It would seem like it would stop leaking for a while, then it would start again. After about a year I found out about that bolt. I put it in and haven't lost a drop of oil since.

Tell me whether or not you have that bolt installed. You should be able to access it from the top.

The reason it might not have leaked earlier is because you had no ring blow-by. Now that the engine is wearing in a little, the rings will blow by some and create some crankcase pressure. That pressure will push oil down the fuel pump pushrod and out that bolt hole. This is why it has only showed up recently. Mine was leaking only under heavy load because that is when there is the most blow-by and the least manifold vacuum so the PCV system stops operating.

Bolt is in. I put a more aggresive cam in last year 218/224 at duration 0.05 lobe seperation 110. Since then when I get on it I had blow by. I used my other valve cover(not the one with the pcv valve) and used a breather cap with a fitting for a tube to vent my fumes down my carb. It works great. Took it out again tonight after checking all my gaskets to see if they were sealed properly. Ran it up to 70 and then cruised at 60 for about 15 minutes. Pulled it in my garage and had no oil leak. The night before I had pushed it hard to around 90-95 and now am wondering if my cam is causing to much pressure, but even though that might be I cannot find the leak.

Denny This is my set up.

That's not pulling any vacuum in the crankcase, though. You've got to go to one of the vacuum ports on the carb for best results. Not one that sees direct manifold vacuum, but one that goes to the venturi of the carb but is still above the butterflies.

Works for me.

Don't know what the hell is going on with my chevy but took it out this afternoon, ran it up to 100, held it there for 2 miles(if it blows, it blows) brought it back down to 65 and ran it there for 5 miles and parked it with no oil leak. Two weeks ago I rebuilt my 350th tranny and didn't put in a shift kit. With my high gears it seems to hold at 75 in 2nd gear before dropping into 3rd. Might have a pressure built up that one day which causes it to push the oil out the pan

Originally Posted by chevy 37

Don't know what the hell is going on with my chevy but took it out this afternoon, ran it up to 100, held it there for 2 miles(if it blows, it blows) brought it back down to 65 and ran it there for 5 miles and parked it with no oil leak. Two weeks ago I rebuilt my 350th tranny and didn't put in a shift kit. With my high gears it seems to hold at 75 in 2nd gear before dropping into 3rd. Might have a pressure built up that one day which causes it to push the oil out the pan

Next time you change the oil put 5 quarts instead of 6 and I bet that leak stops.

Never have put more than 5 quarts of oil in any of my cars(all 4). Not that dumb although sometimes I wonder.

76GMC1500

I read with interest your description of the open tapped hole in the Chevy 350. Sure enough, mine has that hole straight into the fuel pump rod, and with nothing in it. Wide open! Man, I have never noticed that. It might explain my oil leak that started happening recently. My engine has about 700 fairly easy break-in miles on it and since starting it after having the engine rebuilt and in the car, but not having been started for about 8-10 years. Only lately after highway driving have I notice oil up around the front of the engine. It won't show me anything at idle. I have just installed a short bolt with Teflon tape around it a couple times, and a washer under the bolthead. If this works it would certainly lighten the winter work on my '40 PU. I can't believe this is not common knowledge around Chevy circles. You said this is open and tapped, by GM, only for keeping the fuel pump push rod from sliding down while installing the pump? Nice plan, but why in hell don't they put a bolt in it afterward? I'll let you know how things go with my Ford PU. Thanks

Elder Rodder

hhhmmm very interesting......this sounds like the mysterious earl leak my motor had when it was in a family friends coupe....it started when the motor was 6 or 7 years old....oil all over the passenger side of motor and firewall when running at freeway speeds 65-70 or more.

I still have a couple months before i fire that motor up after a rebuild, we didnt find anything off or weird when taken apart, we assumed it was the timing cover, but i will make sure that i put a bolt in that motor mount hole.............good info in this thread