If he has teflon seals, they are not causing a visible black cloud....they do sometimes promote accelerated wear depending upon guide material and stem material. Metal clad viton seals are smaller in diameter and will fit fine.

You may have an intake gasket that is allowing oil to get into the intake port under high vacuum situations (such as sitting at a stoplight at idle), this is a common problem with the SBC.

 

If ya have accelerated wear from the teflon seals and the build as done 4 years ago like this one, then the seals are worn out from the valve being loose in the guide and if replaced by neoprene rubber with a wire spring around the stem or even the old umbrella style that will get it done.
Learned about PC type teflon seal 40 years ago on a sprint car and they ain't good for any duty much less street duty.If ya want worn out heads in 5000 miles go ahead and use them but guides and worse head with no guides that have to be machined to install guides to save the head is costly. IMO it is better to use a seal that let's a mist of oil by to lube the guide and that ain't enough to cause detonation-- What PC teflon seals are advertised to eliminate.

Intake gaskets are NOT prone to leak if the angle of the two faces are correct and it is torqued.If there is a difference it should be corrected long before the intake is installed.If the gasket was installed wrong and there is a gap or the gasket moved uncovering the port, that doesn't seal ya will have a miss,vacuum leak,weak cyl,and possibly fuel in the oil.

 

First off - guide material technology has changed a lot in the last fourty years, with the guides and valves I use on our oval track cars, the heads can be torn apart after 2 seasons and show no wear on the guides or valves. Teflon seals in our street motors work great too, we have several motors that came apart after a couple years and many thousands of miles for cam changes and/ or port work, the guides and valves look great. Accelerated guide wear has a lot to do with heat in the exhaust system and having a good afr tune, vaccuum leaks will cause intake guides to wear out also. I'm not saying you are wrong about the seals, in some cases they are not right for the application as I pointed out above, just in my experiance they have a good reputation.

Half the cars that come to us for dyno tunes end up being found to have intake leaks, so I consider that to be a somewhat common problem, and at least somethig to look into.

 

A more sure way of checking is to loosen the header and look into the port. Black streaks on the valve stem will confirm the issue. Let me know which seals you go with. I'm facing the same issue on my supercharged car which has isky dual valve springs. I'm told the Felpros would work. FEL-SS72861

 

well I found the problen a few months ago , it turned out that 2 of the valve guides had droped into the combustion chamber about 3/4 to 1" , causing the problem , I was lucky that they didnt jam the valve up. anyway these problems led to me doing a rebuild , and I am now using viton seals they seem to be working great , I dont know the part # but I can get it if you want it. as for the teflon seals they seemed to be sealing well on the rest of the stems.

 

Doh, I didn't even check how old the thread was. LOL!! Yeh, if its not too much trouble post up a part number. I fear I may have to break my motor down too but I'm going to take it one thing at a time.

 

yea I can post it tomorrowfor ya. oil running down the fallen valve guides like a drain was the leading cause of detonation and forced me to a rebuild.

 

My situation is a little different. I'm getting oil fouling in every cylinder. The plugs don't even last 1K miles. It coughs when I romp on it and a big puff of smoke out the back. If I ease into it then it runs well though.

 

Glad ya found it and glad the new seals are working out.

 

One thing about teflon seals that wasn't mentioned is that they aren't as flexible as neo or viton. If you do happen to have a worn valve guide and the valve is moving around a little, the teflon seal might not do it's job as well as another type.