Best Valve Stem Seals ?

[AMXguy]

My new 440 has the same problem with the valve stem seals my other one had, this time it isn't going to take me two years to figure out it's the junk white teflon positive seals. they positively leak must be what that means, I knew I should have changed them before I put the heads on.

 I replaced them with viton umbrella seals last time and it 100% cured my oil burning. now I want another set and nobody can find them, anyone know who makes those or something else as good?

[72rtchallenger]

i think you can still get viton umbrella seals at jegs or summit

[AMXguy]

I just thought of a snag maybe, does anyone know if the umbrellas will fit inside dual valve springs? I may be stuck with positive viton seals.

[AMXguy]

The more I think about this the more I think they won't fit I willl need positive style Manleys or something., by dual I mean two springs and a damper spring . the other issue is I have new bronze guides and new valves, do I dare starve them too much for oil until they have some miles on them or does it matter?

[72cudamaan]

A viton seal with a teflon insert is a great way to go. The rubber seal allows a bit of flex to compensate for the clearance in the valve guide, while the teflon is rigid enough to scrape the valve stem. Any machine shop can get these if they don't stock them.No, you don't have to break in the heads before installing these. They should work just fine.

[femtnmax]

IMO the teflon does not allow enough oil past it for the exhaust valve stems.  They need lubrication to help transfer heat out of the valve stem to the guide.  The exh valves and spark plugs are the two hottest locations in the combustion chamber, thus likely locations that can promote detonation. 

[Chryco Psycho]

I would use the steel body seals with the rubber liners , they are thin enough to fit inside the dual springs

[AMXguy]

You mean the steel/viton ones or just the steel/nitrile cheapo's ? not to say they're no good but I only want to do this once.

[jimynick]

AMX, the gold standard seal has been the Perfect Circle seal for decades, BUT- you've got to machine the guides to their size AND you've got to make sure that the cam/spring/retainer package that you use doesn't hit them at full rocker arm lift or all bets are off. The old umbrella condoms will take being bashed around a wee bit, but the PC's won't.
  Off topic a bit, but I think I read that someone was offering a redesigned timing cover/oil pump for the AMC's to cure their habit of chewing enough aluminum off the bottom of the oil pump chamber to kill 'em. My buddy bought a 68 AMX 390 in 68 and that's what killed 2 engines.