My Engine (350) leaks oil, The under side of the engine and trans has oil all around it. When I park the car a few drops are on the garage floor. I'm thinking rear main is leaking. Just wondering if any oil leak additives can really help stop this. I'm am going to change the valve cover gaskets, seems to be oil in and around the spark plugs ( Little puddle of oil by spark plugs).
Also what is the best grade of oil to use. I was told not to use a 5w30, to light of oil for these older engines. So I was thinking a straight 30 weight.
Just wondering what everyone else runs in there engines. Thanks Barb.

 

My 350 was an oily mess when I first bought it. When I started it, it blew smoke everywhere from oil that ran down on the heads and exhaust ports and manifold. The main problem was fixed easily by replacing the valve cover gaskets. If you have a rear main seal leak, changing oil won't do much. See how it is after the valve covers and a good cleaning. Next would be the oil pan, timing cover and the front cover seal to the crank snout. That is a lot more work than the valve covers. 95% of my leaks ended with the valve covers.

I would use a good multi viscosity oil like 10W30 or 5W30. Straight weight doesn't help much at start-up, when most engine wear occurs, especially in cooler weather. Some people suggest a heavier oil, but articles I have read point out that while heavier oil does increase oil pressure, it doesn't get more oil or more pressure to the bearings. The heavier oil builds more pressure at the pump to push the oil, but less oil flow to the bearings. An extreme example would be to use 90 weight gear oil (which you of course wouldn't do). You might burn up the oil pump building pressure off the chart, but no oil would reach the bearings. I use 10W30 and my engine has over 200K on it and burns almost no oil between changes.

 

Thanks for the response. I'll change the valve cover gaskets and see if that helps. I thinks it's leaking on the bottom also, but if it's not to bad after the valve cover gasket change I think I'll just have to live with it. Also the oil leak additives for sale, you know there suppose to stop leaks in old engines. I'm sure it does'nt work just wondering what you thought about it.
Thanks again, Barb.

 

10w30 is what you want, unless you drive during harsh winters, then 5w30 is okay.
I would avoid the leak stoppers, as they will prolly cause more harm than good over the years. Valve covers are usually big leakers, so start there and use the rubber gaskets.

 

Cover the distributor, carb and alternator and spray the engine down with degreaser. Rinse all of the degreaser off and start the car and let it run for a few minutes to build oil pressure. See if you can spot the leak as it happens, there are also dyes made for this.

I spent a lot of time chasing oil leaks on my 455 around the engine only to find that it was all coming from the fuel pump, so keep that in mind as well if you have a stock piece.

 

Mine leaks from the fuel pump and from the broken dip stick hole.

 

Another semi-common leak location is the the oil filter adapter. Three bolts to give a slight snuging to the block. The gasket is still available through many DIY parts shops. Mine dripped from there, coating the whole underside of the pan. Drive a bit and the oil blows everywhere.

Adam

 

valve covers as already mentioned and the rear main, especially if the original rope seal and engine has some miles on it. recently replaced the rear main in my 150K mile 350, first time the drivetrain was out of the car. rear main was leaking BAD, might as well just poured oil on the ground. used a neoprene seal along with getting all the nylon timing chain gear bits out of the pan and pump pickup. so far so good, although I've yet to drive it. I've just let it idle in the garage, but this allowed me to discover a radiator leak. it's always something.

 

Thanks for all the great ideas, I never thought about the fuel pump or dip stick hole. I bought a set of valve cover gaskets, but they are the cork type. So I think I'll see if I can get rubber gaskets. OK! Thanks to all of you and on we go, If nothing else I'm learning alot from all of you and this car.
Barb.

 

Don't forget the rubber strip seal on the back of the intake manifold - if this is blown out, oil mist can blow back and drip down the back of the engine, and you'll never see it.

- Eric

 

i read somewhere that synthetic oil causes that rear main rope seal to harden and weep oil, any truth to that? i switchd to synthetic, started getting small oil leaks then a major one but it was attributable a cracked valve cover. after i swapped that out i'm back to one small drop everytime i fire it up which i can live with but it was drip dry before i changed to synthetic. i've since switched back.