GMC Truck Forum banner

1 - 6 of 6 Posts

·
Registered
Joined
·
470 Posts
Discussion Starter · #1 ·
I am pretty sure I have a couple of cylinders gas washed on a '97 350 marine engine. Is there some sort of magic trick to get those to stop burning? Compression is awesome (163-175 on all), leakdown is great. When I went through the motor after I bought the boat, the last mechanic to work on it had used a standard plug in the vortec heads, which are about .5" too short. Motor was run for about 6 hours with those before I pulled a plug to check on the oil burning.

I have been experiencing oil burn, and oil fouled plugs on the front cylinders. I am tired of going to the parts store to purchase a quart 40W oil after a day out. I replaced valve stem seals already. Motor is super clean, valve springs still have paint on them. The stem seals were getting brittle, but it is apparently not where oil is getting into the cylinders.

The other thing I was thinking is that maybe the intake (performer RPM) is sucking oil down through a bad gasket (I have seen this on big blocks) and possibly getting the oil into the cylinder there?

One other thing, I am rejetting b/c the motor is running a little lean. Is it possible the engine being lean is causing some of this?

There was also a small amount of oil I assume from the blowby on top of the intake after the last time I went out.

Ideas?

Motor is a '97 350, vortec heads, holley 600cfm 4bbl, edelbrock performer intake, hydro cam.
 

·
Im walking on sunshine!
Joined
·
5,651 Posts
(I have been experiencing oil burn, and oil fouled plugs on the front cylinders.)And the seals are good..Man thats a weird problem, I will ask a buddy of mine who does boat motors and cars and trucks..:hmm:
 

·
Registered
Joined
·
999 Posts
do a leakdown test. it will tell you where your problem is.
 

·
Registered
Joined
·
470 Posts
Discussion Starter · #5 ·
Yeah on the leakdown, there was one cylinder that was fast.....tapped the valve, hit it again and it was fine.

The oil is getting mixed in on the topside I think, not blowing by the rings, unless they are gas washed. The cylinders in the front are oil fouling and get progressively better further back. The front two are black, the next are a little black, the others have no signs of oil. The engine is running lean though, so maybe that will have something to do with it; which is why I am jetting up. I still think I might have one of those funny leaks letting the intake suck oil in from the gasket. I guess that will be the next step....reseal the intake.

That leaves me with possibility gas washed cylinders (caused by the short plugs).....which would be the same symptoms I think, but i don't know b/c I have never experienced it before. Does anyone have any ideas on how to magically get the cylinders that got gas washed mo' betta'?
 

·
HOT AIR BALLOON OWNER
Joined
·
14,932 Posts
1 - 6 of 6 Posts
Top