ring problem in my 350?

Hello all and happy Summer.
I have had a fouled plug in my #8 cylinder for the second time now which has been causing the plug not to fire.
The plug is caked with a build-up of oil residue when removed. A mechanic said it's a ring failure and the engine needs to be rebuilt.
Someone said I might get lucky and be able to replace only the ring if the block is not damaged. I have not done any other testing yet, compression, etc so that is my next step. Opening up the engine pulling the piston and researching is in order.
What do you folks think?
Thanks and have a great day.

 

I've owned a few sbc that did that. Valve guide wear, lets oil down though on the intake stroke, and does drain down into the intake port when shut off.

My guess is guides.

You might get by this season with a different style of plug, going from exposed, to a recessed electrode, or a hotter plug. In desperation, you might try a spark plug extender, if you can still find one.

 

That's kinda a big job to pull the motor ,tear it down etc. for just one piston ring. Actually it would be stupid. If you are gonna go that far just rebuild it. Or if your budget doesn't allow the cost of a rebuild a used motor could be a good choice. Your oil fouled plug could be caused by a valve seal too. Have you done a compression check or leak down test yet? You really need that to help make a proper decision on how to proceed with your motor. Good Luck! N.N.

 

intake gasket is sucking oil.

 

Time for a leakdown test.

 

If your rings were bad, it would usually smoke heavily and use lots of oil. You could pull the valve cover to see if the drain hole in the head is plugged building up oil on the valves so it leaks through the guides. Usually a heavily fouled plug without a lot of smoke is from oil coming past the intake valve guide. You can put new seals in without tearing the engine down.

It could also come through the positive crankcase ventilation valve.

What oil are you using? You might try an ashless oil like Valvoline racing oil and use a heavier weight oil. Many quick lube places put 5W-20 in everything these days and that's what most newer vehicles are designed for. I like to use straight 30 in older engines. Straight 40 if they use too much oil. Hotter plugs help and make certain you have the correct plug for the head being used and go up one heat range.

 

If a compression test shows #8 way down on pressure then the rings may be the problem. If compression seems pretty even in all cylinders, even if it's a bit low, then consider checking the valve guides and seals.

Oil getting past a valve guide, usually an intake, will show itself in a couple different ways. Do you see a puff of blue-ish exhaust smoke occasionally when first starting the engine? How about when the engine is idling for longer periods? Or maybe when decelerating like coasting down from speed with the throttle closed?

If the guides are really hammered that means replacing them and the seals and having the valves ground. But if you're on a budget you might get some relief temporarily by just replacing the seals with new umbrella seals, and maybe just on the intakes. And you can likely do this without pulling the heads.

 

Are you running an automatic with a modulator? Could be sucking trans fluid, not engine oil.

 

Thanks for all your patience and advice.
The car has Edelbrock rpm heads and Edelbrock Air Gap intake.
These items were on the engine when I bought it 2 years ago, and were pretty new (I'm told)
The car is running a 700 r4 with non lock converter.

I can not see smoke while driving or on start up.
I have noticed that when I put my foot all the way into it the smell of the exhaust has gotten sort of sour and does not have the sweet raw fuel smell it used to have (The car is a wagon and I often drive with the rear glass open)

Next on my list is to get in to get this leak down test.

Thanks again and have a great day.

 

Hi folks and happy holidays.
Well, HAMB member randydupree called this one.
Thanks for all your help.
My mechanic replaced the valve seal even though it looked like it wasn't that bad.
Then he pulled the intake, and the gasket was bad in the rear passenger side.
I was surprised how poorly the Edelbrock intake gasket that goes with my RPM air-gap intake actually matches the ports.
Not only was the intake torn in this area but there was gasket overhang into all the port areas.
We replaced the gasket with a stock GM one and the car is running great.
Thanks again and have a great day!

 

Thanks for the update. I like to glue the intake gaskets to the heads so they don't move as the intake is installed.