PC seals for SBC exhaust valves

[Clone TIE Pilot]

My L69 305 has recently started to smoke and I suspect its the valve stem seals. I pressume the seals are original. The engine still has excellent compression. The 305 has stock 416 heads which from the factory use viton PC seals on the intake valves with O rings and the exhaust valves use umbrella seals with O rings. I was wondering if its possible to install PC seals on the exhaust valves too without issues?

 

[69hurstolds]

If there's enough room inside the spring, and your stem/guide clearances are good, I don't see why not. I know a few Chevy guys who've done it and never complained of any issues doing it. Of course, valve seals isn't a subject that comes up a lot. Some of the hardcore racer guys I knew didn't even bother with seals, so whatever they had to say about it didn't matter.

 

[Clone TIE Pilot]

I looked around the Thirdgen forums and several guys posted they have run intake positive seals on exhaust valves without issues. Low emission engines tend to use positive valve stem seals at least on the intake valves for better oil control and reduced emissions. PC valve seals also help extend spark plug life.

 

[bracketchev1221]

We used to mess with the exhaust seals to try to get more oil down the exhaust guides to keep them cool. We used to put the seals on and take the spring off around the stem so it wasn't as tight. Never went without a seal at all though.

 

[64nailhead]

If you’re taking the heads off to install the seals, then it’s easy work to cut the head to accept a positive seal. If you’re going to try it with the heads on the car, then you’ll have to find a seal that will fit over the head ‘stem’ for the guide.

I’m not familiar with the 416 head, but I know positive seals are available in most every SBC head arrangement that is found in a 350. Are the ‘stems’ the same in a 416 as every other SBC - I don’t know. But pulling the heads, getting new valve seals and getting a valve job done wouldn’t hurt anything. It will cost you some time and a set of HG’s and intake gaskets.

 

[Clone TIE Pilot]

I am leaving the heads on as all the cylinders show high compression with my tester. 416s are the head castings many 305s have and they do come from the factory with PC seals on the intake valves.

 

[Clone TIE Pilot]

You can nearly count on the snowball effect. I removed the exhaust spring from cylinder one and found it has a cracked damper. Time for new valve springs too.

 

[spongbob]

A little odd info I once heard an old guy some time ago: mentioned exhaust stem seals he" said.... that the positive exhaust pressure would blow oil back up the exhaust... but that the intake was where the oil was sucked down ...sames Tru of old rotton/loose intake gaskets. Okay questions aside": I have a suspicion it's possible for oil to leak from some valve covers and into the manifold enough to produce smoke. I have expeiriance with certain oil being thin and smokey where as (valvoline/ penzoil) wheras Castrol was less leak prone...I like to run thin oil but you have to have good seals to do so...thus is were"! havoline comes in its" thin heat dissipating to the point of reseating old rings even.... getting having heads with tight guides means half of everything you consider about your engines happiness seems like there's some law that prohibits one from acquiring heads with tight guides. Getting work to the guides ? about half the chance they will be loose even then..I don't want to discourage you but this is the ground I have been over...yess I have a set of 416s setting in my car port I need to get some new intake valves, dew to rust but they are ever as tight (guides)as ever i have seen on such heads

 

[abbey castro]

I did the screw in studs on 81 Vette 350 and installed Sealed Power valve seals, that was in 1985. Car has few miles but no smoking at start up or anytime.