350 Spark Plug issues

[SquareRoot]

Let me guess; You used the Edelbrock intake gaskets? I had the same exact issue on a new Goodwrench crate motor after swapping to an Edelbrock manifold. Intake manifold gaskets are leaking on those ports and sucking oil in. Stay away from laminated type gaskets. Use the fel-pro O-ring style gaskets. I have a thread on here somewhere about it complete with pics.

 

[Matt69olds]

What kind of valve covers are you using? Do they have baffles around the PCV valve? If not, the PCV valve is probably sucking oil right out of the valve cover.

I built a 455 for my brother in laws 87 cutlass, it’s a pretty rowdy street car. He bought aftermarket cast aluminum valve covers to put on it, while the looked good, the quality left much to be desired. For some reason, the Chinese decided to cast and machine the PCV bore directly over one of the pushrods. Basically, whenever the engine is running, oil is sprayed directly into the valve. Ever seen a runaway diesel engine? It smoked almost that bad. He was ready to pull the engine back out thinking I broke a piston ring or screwed something up during assembly. We went thru the same tests, excellent compression, excellent leakdown, just couldn’t run the engine vin an enclosed space for more than a few seconds before you couldn’t see anything.

Make a long story short, stock valve covers and double gaskets solved his problem, once all the oil burned off.

 

[Snoots]

^^^ What @SquareRoot said!

 

[MelbGMC]

Let me guess; You used the Edelbrock intake gaskets? I had the same exact issue on a new Goodwrench crate motor after swapping to an Edelbrock manifold. Intake manifold gaskets are leaking on those ports and sucking oil in. Stay away from laminated type gaskets. Use the fel-pro O-ring style gaskets. I have a thread on here somewhere about it complete with pics.

Felpro gaskets were used on the inlet manifold

 

[MelbGMC]

What kind of valve covers are you using? Do they have baffles around the PCV valve? If not, the PCV valve is probably sucking oil right out of the valve cover.

I built a 455 for my brother in laws 87 cutlass, it’s a pretty rowdy street car. He bought aftermarket cast aluminum valve covers to put on it, while the looked good, the quality left much to be desired. For some reason, the Chinese decided to cast and machine the PCV bore directly over one of the pushrods. Basically, whenever the engine is running, oil is sprayed directly into the valve. Ever seen a runaway diesel engine? It smoked almost that bad. He was ready to pull the engine back out thinking I broke a piston ring or screwed something up during assembly. We went thru the same tests, excellent compression, excellent leakdown, just couldn’t run the engine vin an enclosed space for more than a few seconds before you couldn’t see anything.

Make a long story short, stock valve covers and double gaskets solved his problem, once all the oil burned off.

I'm using Edelbrock Elite valve covers on the motor

 

[MelbGMC]

Well It looks like it is valve guides, the leak down test didn't show up any issues, which was good.
I'lll be taking the heads to a machine shop come Monday and get the expert opinion from them.

 

[MelbGMC]

I've had the heads off to the specialists to get assessed and they have come back with an "all clear" The oil may have been coming from the intake manifold gasket not being thick enough, or a warped intake manifold. I'm going to measure up the inlet manifold and replace the PCV valve, valve covers and install thicker intake manifold gaskets over the next few days. Fingers crossed this solves the issue for me.....