Most of this is covered in the Gasoline Engine write ups in the BP Knowledge base. Just click and read.Valve guides are lubricated by a thin film of oil.Doesn't matter if it's oring, umbrella or PC.The lead in fuel was to lubricate the seats not really intended to lube the guides. That's why hardened seats were recommended for engines with soft metal castings once lead was removed.IH has a high nickel content so the swap to hardened seats wasn't a real priority if the engine didn't already have them.The fuel cools the intake seat and valve so there isn't as much need for hardened seats.The umbrella seal does not prevent the stem from getting lubrication.It simply creates an umbrella to shed off excess oil from running down the stem and pooling on the guide.The oring and the umbrella will ride up and down with the valve. so the stem is always exposed with the oring.There is always oil vapor present in the valve cover as blow by and the splashing of oil from the rockers and pushrods fly up and down.As for PC seals, they restrict the majority of oil from entering the guide.BUTThey still have a thin film of oil on the stem as it passes through the seal.Most machine shops and manufacturers add silicon bronze inserts in the guides or an alloy to prevent galling/seizing that may occur with metal to metal contact.I have heard that a few run steel guides with PC seals but haven't seen it.My thought would be the clearance would be a little more.
Registered User
Join Date: Apr 2009
Location: New Freedom Pa.
Posts: 1,335
Re: 454 Valve Steam Seals: Umbrella or Positive?
Be aware some of the "positive" seals you have shown require machining at the the guide area for proper installation . only the "umbrella" style fit everything.
Desert
Here is a quote about the process I mentioned above form another site.
"Teflon or Viton positive stop seals are installed on a guide boss that has been machined to 0.530" diameter for a 0.001" interference fit and the seal bottoms on the valve spring locator boss. The stock Chevy spring locator boss is generally about 0.900" OD and must be machined smaller for dual valve springs. The Teflon and Viton positive stop seals has a spring that tightens on the valve stem and a spring that tightens on the valve guide boss and must be used with dual or triple valve springs. The one you have are Viiton rubber umbrella seals and they do not have a spring that tightens on the the valve stem.
Umbrella seals allow a small amount of oil to pass into the stock iron valve guide for valve stem lubrication. Virtually no oil gets past Teflon or Viton positive stop seals and that is why you should install K-Line Bronze Bullet (or equal) phosphor bronze valve guide liners to use those type positive stops seals. Bronze guides or guide liners have "self lubrication" characteristics."