Valve Stem Seals
Posted: Tue Oct 26, 2004 1:37 am
Pioneer brand #OS-1072 (USA), 10.5mm guide, 5/16" stem, .38" length, positive type , spring-loaded teflon Available at Pepboys, Autozone, Kragens.....almost everywhere in the states.
<a href='http://www.pioneerautoinc.com/index.htm' target='_blank'>http://www.pioneerautoinc.com/index.htm</a>
-Modify steel spring washers as shown on the left-hand side with a 9/16" (.56) hole to clear the seal's .54" OD.
-The valve retainer keepers must be shortened by .06". Grind away the material being careful to not overheat the hardened keepers thus annealing them.
-Cut OD of guide to 10.5mm and shorten by about .06" so the seal butts against the shoulder or wire ring on the guide which stops the guide from slipping too far into the head. Radius the edge a little to allow the seal to be pushed on without chafing it. These cutting tools can be purchased. Used a battery powered hand drill to do the work.
-Trim the plastic installation tool sleeve in length so the closed end butts up against the end of the valve stem amd long enough so it cover the keeper grooves.
-Use synthetic oil. The amount of oil making it past this seal is only a few monolayers thick I'm guessing. That's plenty with a tough-chained hydrocarbon oil like the synthetic. Not sure dinosaur oil will be okay.
This only works for a cam with .35-36" of lift. The small end of the seal actually enters into the tapered pocket through hole for the keepers in the spring retainer. That's why the keepers need to be shortened. IIRC, if the valve does not float there is .05" clearance between the seal and the keepers. It's close but works great. The seals need replacing about every 50k miles. This particular size of seal was chosen because it's OD clears the ID of inner valve spring so there is no contact. Most importantly it's rather short at only .38" in height where as almost all the other cloices of seals are at least 1/2". Heard the argument that shortening by any amount the bronze guide is a mistake. Actually what the seal does is add a rather stiff linear bearing structure with an interference fit onto the the end of the guide. If anything it makes the valve stem stay centered in the guide with higher precision and possibly provides lateral dampening. After 50K miles my guides measured zero wear. This link below takes you to the folder 'Twincam Valve Stem Seal'
<a href='http://briefcase.yahoo.com/[email protected]' target='_blank'>http://briefcase.yahoo.com/[email protected]</a>
-Keith
<a href='http://www.pioneerautoinc.com/index.htm' target='_blank'>http://www.pioneerautoinc.com/index.htm</a>
-Modify steel spring washers as shown on the left-hand side with a 9/16" (.56) hole to clear the seal's .54" OD.
-The valve retainer keepers must be shortened by .06". Grind away the material being careful to not overheat the hardened keepers thus annealing them.
-Cut OD of guide to 10.5mm and shorten by about .06" so the seal butts against the shoulder or wire ring on the guide which stops the guide from slipping too far into the head. Radius the edge a little to allow the seal to be pushed on without chafing it. These cutting tools can be purchased. Used a battery powered hand drill to do the work.
-Trim the plastic installation tool sleeve in length so the closed end butts up against the end of the valve stem amd long enough so it cover the keeper grooves.
-Use synthetic oil. The amount of oil making it past this seal is only a few monolayers thick I'm guessing. That's plenty with a tough-chained hydrocarbon oil like the synthetic. Not sure dinosaur oil will be okay.
This only works for a cam with .35-36" of lift. The small end of the seal actually enters into the tapered pocket through hole for the keepers in the spring retainer. That's why the keepers need to be shortened. IIRC, if the valve does not float there is .05" clearance between the seal and the keepers. It's close but works great. The seals need replacing about every 50k miles. This particular size of seal was chosen because it's OD clears the ID of inner valve spring so there is no contact. Most importantly it's rather short at only .38" in height where as almost all the other cloices of seals are at least 1/2". Heard the argument that shortening by any amount the bronze guide is a mistake. Actually what the seal does is add a rather stiff linear bearing structure with an interference fit onto the the end of the guide. If anything it makes the valve stem stay centered in the guide with higher precision and possibly provides lateral dampening. After 50K miles my guides measured zero wear. This link below takes you to the folder 'Twincam Valve Stem Seal'
<a href='http://briefcase.yahoo.com/[email protected]' target='_blank'>http://briefcase.yahoo.com/[email protected]</a>
-Keith