Flat32: 4/1/2000 - 4:39:30 PM
Valve stem seals
I'm installing valve stem seals on the intake guides. I'm beginning to wonder if they will work too good and not allow any oil to the valve stem. How dry can a stem run? Is it possible I should modify the seals to let some oil past? Or am I making mountains out of molehills?

john l: 4/1/2000 - 6:30:51 PM
RE: Valve stem seals
I'm rebuilding my '53 v-8 and it had seen some work before. seals only on intakes, not modified and the stems all looked fine. not to worry!

Russ: 4/1/2000 - 11:05:52 PM
RE: Valve stem seals
I'll have to defer to the experts on this one, but it does make me question the need for seals. I was under the impression that very little oil gets into the valve galley. That what gets there is only a oil vapor. Can the experts comment on this, as I am at the point of deciding wether or not to use any stem seals.

Tom Zurn: 4/1/2000 - 11:13:57 PM
RE: Valve stem seals
Yep. mountains out of molehills, just be sure to coat the valves and seals with a good alathering of motor oil to lubricate valves and seals on start up. You should really check your stem to guide clearance, It should be within specs.

erbssr: 4/2/2000 - 9:51:05 AM
RE: Valve stem seals
I think the purpose of stem seals is to prevent blow-by & therefore reduce oil consumption. When they are worn you can use a lot of oil especially at high rpm.

rodnut: 4/2/2000 - 12:42:34 PM
RE: Valve stem seals
My opinion: In an o/h valve engine, the valve stems and guides are awash in oil and the oil will flow down the stem/guide (gravity) due to their placement (stem up), as well as from vacuum - a seal is necessary. But, since the valves in a flathead are upside down (stem down), this amount of oil is not present. If a seal is used, it could lead to sticking valves due to a lack of lubrication here. If the engine smokes due to no seals, then the stem to guide clearances are excessive. Keep your intake guide to stem clearances at .001 - .0015'', with exhaust .001'' more, with one-piece guides. DON'T use two-piece guides, as they require excessive clearance due to the instability of the guide halves! Your engine should easily get 2500/3000 miles before consuming a quart of oil, and by then it's time to change oil anyway! If you get less than this, your engine needs looking at, 'cause something's wrong.

rodnut: : 4/2/2000 - 12:46:49 PM
RE: Valve stem seals
My opinion continued: I forgot to mention: Another good idea is to replace the squarecut o-ring guide to block seals with Viton o-rings. They will not shrink or harden from heat, maintaining a good seal for the life of the engine!

JWL: 4/2/2000 - 1:41:00 PM
RE: Valve stem seals
As to how dry they can be run, it depends on the type of material, the clearance, and the amount of heat. Stock materials need some lube. The appropriate modification might be to forget the seals, be sure the baffles are in place, and the clearance is not excessive. If you install bronze wall liners, you can safely decrease the clearance and use stem seals. Some people talk as though the clearance is something you can control when you assemble the engine, but even with a large stock of new parts, it may not be possible to find a combination which provides the clearance you want unless you install liners and hone them to fit the application. In my opinion, this too has marginal value.

rodnut: 4/2/2000 - 2:32:42 PM
RE: Valve stem seals
I've always been able to mix and match valves/guides in my motors to get the clearances I mentioned. Even had to hone a few. I always purchase two or three extra guides (they're cheap, relatively) in case one may be too large, but so far have been able to keep within the max clearances I mentioned. I also use only QUALITY, name brand parts! Manley small block Chevy s/steel valves are excellent, and reasonably priced, and can be used for both intake and exhaust. Bronze liners can be used, but I feel it's a lot of extra work. A good quality cast iron guide and a chrome v/stem work very well together with the forementioned set-up. I tried bronze liners in my early Hemi motor, with tighter than stock clearance and P/C seals - I got about twenty miles and stuck two valves!! Re-did heads w/ iron guides and min stock clearances, same seals - no worries, mate! Engine ran great for years! Personally, no more bronze inserts for me - - -

Flat32: 4/3/2000 - 3:53:51 PM
RE: Valve stem seals
The lifter valley apparently gets quite a bit of oil even with the baffles in place judging by the amount of sludge in there on an old engine. My valves are new with chrome plated stems, guides are new, but have .002 clearance. I don't have an option on clearance and decided not to do bronze liners. The seals I decided to use after seeing how fouled up the underside of the valves can get from excess oil going up the stems. I'll agree the seals aren't needed if the stem clearance is within specs, but parts do wear and how long they stay within specs is something I don't know. I'm assuming the exhaust valves run very dry and assume I'll need to allow some oil past the seals. I'll cut a couple tiny grooves in the seal surfaces and hope for the best. Thanks for all your input.

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