Valve Seals!

885speed · Feb 24, 2020

PANHEAD said:
the text says 305.. the worst chevy enging next to a 307 do u even know what a panhead is????

why waste money on a 305

First thing, that was me referring to the 305 in my other vehicle. Not the OP.
if a $70 whole engine gasket set and my own time and labor is "a waste of money" on a good running engine that needs nothing else, then I must be some special sort of A-hole that likes an engine that doesn't leak oil or smoke due to bad valve stem seals..

Second thing, take notice how everyone in this thread has been posting responses that are CONSTRUCTIVE or HELPFUL.
That is until you came along and interjected your opinion, which is neither constructive, nor does it have anything to do the point of this thread.

Uncle Grimace - great info, thanks for sharing that. Definitely helped me decide which seal/material I'm going to use.

PlayingWithTBI · Feb 24, 2020

Pan Head, Knuckle Head, Shovel Head, who cares? This site is about GMT400 trucks.

Erik the Awful · Feb 25, 2020

I would have liked to use positive valve seals on my 350, but I put a .515/.520 lift cam in. I didn't do any machine work, and used LS2 valvesprings/Comp Cams retainers. With umbrella seals I can run up to .550 lift before the seal gets pinched. With positive seals I was looking at a max of around .500 lift.

cngodfather · Feb 25, 2020

Hopefully machine work will not be necessary and i can still use positive seals. My lift maxes at .500 lift and I went with +.100 valves. I will measure first though. Thank you all for your help.

Redneckgeriatric · Feb 25, 2020

Erik the Awful said:
I would have liked to use positive valve seals on my 350, but I put a .515/.520 lift cam in. I didn't do any machine work, and used LS2 valvesprings/Comp Cams retainers. With umbrella seals I can run up to .550 lift before the seal gets pinched. With positive seals I was looking at a max of around .500 lift.

you would have cut the guide for the seals at the same time you cut the head for the valves and springs. there is really nothing extra to do as you were doing the setup for the other components anyway. im guessing the recipe you followed is one of those "it'll work" deals. valve geometry usually doenst come into play on those.

Erik the Awful · Feb 25, 2020

With Vortec heads and valves, LS2 springs, and Comp Cams 787 retainers you don't have to cut the heads for the springs. It bolted together, measured out fine for valve seal clearance, and doesn't bind. The only downside was having to use umbrella seals instead of positive seals. There was no modification of the suspension geometry other than increased lift. The simple explanation is that the Comp Cams retainers are shorter.

cngodfather · Feb 25, 2020

I just measured my clearance between my seal and the retainer. I have .770" between the seal and retainer. I will definately get the postive seals.

cngodfather · Feb 26, 2020

I have heard not to use the positive seals on the exhaust valves and I have heard that it is ok to use them. How bad would it be to use them?

Redneckgeriatric · Feb 26, 2020

i have installed them on a bunch of engines that spun a lot of rpm and pushed head temps. not an issue, what is the supposed reason not to run them on exhaust side? im curious.

Redneckgeriatric · Feb 26, 2020

Erik the Awful said:
With Vortec heads and valves, LS2 springs, and Comp Cams 787 retainers you don't have to cut the heads for the springs. It bolted together, measured out fine for valve seal clearance, and doesn't bind. The only downside was having to use umbrella seals instead of positive seals. There was no modification of the suspension geometry other than increased lift. The simple explanation is that the Comp Cams retainers are shorter.

really? what is installed spring height/ bind height/ installed and over the nose pressures? where on the roller is the valve stem locating as you turn the cam? maybe this vortec head is immune to valve problems, if so, the aftermarket is selling tons of parts designed to correct the issues that will never arise. ?

Valve Seals!

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