Bronze Guides And Stem Seals

[AMXguy]

I'm about to put my 906's together with all new bronze guides , PEP valves and all. I have PEP 38500 silicone positive stem seals, is there anything I should know about bronze guides? do I need more or less oil  maybe requiring a different seal? I've never used bronze before so I thought I'd see if I'm doing anything wrong.

[femtnmax]

I'm running bronze guides too, but I have heard many comments that don't like them.  Too fast a wear rate, or....   David Vizard suggests them in his books for their lubrication qualities, especially for lifts above 0.50.
On the issue of valve stem oiling, a little extra oil on the exhaust stems helps lube the hot valve stems, and helps the heat to transfer from the stem to the guide.  Remember the exh valve and spark plugs are the two hottest locations in the combustion chamber.
So I run NON-positive type valve stem seals on the exhaust.  Some circle track racers I know don't run ANY stem seal on the exhaust, this stopped valves sticking in the guides.  I'm not running a positive type seal on the intakes anymore either, letting a little oil onto the stem should help with valve guide wear.  There's probably an infinite number of opinions to your question, this is JMO.  I don't know if there's anything wrong with using what you have suggested, but I would not use positive stem seals on the exhaust.
The biggest B**ch I have from head work at machine shops is the sloppy valve to guide fit.  There are ideal clearances, and the looser the fit beyond specs the quicker the guides will wear, and the more out-of-round the valve seats are.  It's All bad bad bad.

[71chally416]

  That would be a good idea. Use the type with the metal ring that clamp onto the guide on the Intakes because there is always vac under the Intake valves to draw some lube in, but use the generic "Umbrella" type seal on the exhausts to help get a little oil there. The exhaust port is under pressure so it will not "draw" the lube into the exhaust port. I've never run the exhausts without seals but I guess you could.

For valve guides, it's tough to beat bronze liners. The trouble with the thicker cast iron type guides is you end up with a bunch of valve seat runout when you drill that much metal out of the guide to install them. It's hard to avoid removing that much iron. The liners are much thinner and if done right you lose no valve seat concentricity at all. (I.E. - NO sunken valves trying to get rid of seat runout) Until something better comes along the bronze liners are the way to go. Of course if you have some 30 YO beat up valve stems they probably won't last long. 

[Ck[FIN]]

My friend who has raced many many years said that he takes the metal ring from the teflon seals away, he says the guides will last longer. Seal will not be so tight but still works well.

[moper]

Bronze guides are the best way to do it. They are designed to run tighter than iron guides, which lets you keep seats rounder and keeps the valve motion consisten at high lifts. However, i run a little more clearance than Edelbrock or indy does...lol. On the exh side, I remove the small spring that puts pressure on the valve stem. It's not needed on the exhaust valve. The large flat spring clamp that pressures the sides of the guide should stay, because teflon is like polyurethane bushings... harder and less flexible.

[AMXguy]

The ones I have a silicone, they seal much better than the teflon ones I found this out on my iron guide heads. I have new guides and new valves on these heads so I'm understanding this right maybe I don't want as positive of seal as these silicone ones, I don't really care about wear since I won't put 500 miles a year on this car but In don't want to stick a valve, that's my concern.

[moper]

Seal material has less to do with sealing oil out of the chambers than guides do. I dont recall ever seeing silicone. Or do you maybe mean Viton? It's not silicone but a little nicer than teflon and a positive seal design.

[AMXguy]

I called PEP because I didn't know what they were made out of and they said silicone, I was surprised too but I guess it works pretty good.

 I know teflon doesn't seal ANYWHERE  NEAR as good as viton, after fighting the oil burning on my 440 for 2 years I changed fron teflon to viton and cured it. this was with steel guides though, and a little looser guides, the teflon won't flex with any movement but since these bronze guides are so tight maybe teflon would be fine.

[matt63]

Iron guides are not a good choice.  Silicon bronze guides have good wear resistance.  The guy who put my heads together said he used a positive type valve seal except they had grooves to allow some oil in.  I have no idea who makes these.

[moper]

Teflon and viton are similar, but it's easy to damage the teflons during install, and as you noted... if the valve can wiggle because of typical stock stem to guide clearances, they simply don't seal well.