Valve seals

[workingdan]

I am changing out my valve springs. While I am in there I thought I should chand the valve seals. Is there only seals on the intake side? No seal on the exhust side? Thanks

 

[blown okie]

thats right only seals on the intake from the factory...however if there is enough clearance between the bottom of the retainer & the valve guide, without machining the head ( unless you want to machine the head) i would put a seal on the exhaust valve as well. just my $.02, (i'm sure somebody else will disagree & tell me how wrong i am)

 

[turbofabricator]

ANY seal on a stock exhaust valve will do NOTHING. The stock exhaust valve has a groove on the stem, under the retainer. If you slide a seal over the stem (11/32") it will not seal on this undercut area. The groove is the valve seal, so to speak. It acts like an oil pump. It is tapered at the top, and has a sharp edge on the lower end. It pushes the oil up out of the guide. The undercut allows a certain amount of oil to enter the guide. It is really an oil metering device. If you have aftermarket stainless valves, then you will NEED to have the guides machined down and cut for positive seals. If you run a high lift cam (over .530") then there isn't sufficient retainer to guide clearance, either. (on the exhaust side.)

 

[workingdan]

Great thanks. Just checking, I dont want to to the job twise.

 

[blown okie]

ANY seal on a stock exhaust valve will do NOTHING. The stock exhaust valve has a groove on the stem, under the retainer. If you slide a seal over the stem (11/32") it will not seal on this undercut area. The groove is the valve seal, so to speak. It acts like an oil pump. It is tapered at the top, and has a sharp edge on the lower end. It pushes the oil up out of the guide. The undercut allows a certain amount of oil to enter the guide. It is really an oil metering device. If you have aftermarket stainless valves, then you will NEED to have the guides machined down and cut for positive seals. If you run a high lift cam (over .530") then there isn't sufficient retainer to guide clearance, either. (on the exhaust side.)

agreed, those o-ring seals that go in the groove under the retainer do as much good for oil control laying on the bench as they do installed on the valve with the engine running...i was referring to a "real" valve seal

 

[PaCemkr86]

i always run valve seals on the intake and exhaust... I remeber when i worked for GM and the 4.3 came without them on the exhaust and there was a TSB to install them if the trucks came in for smoking...

I have fixed several TR's there were smoking by installing new valve seals on all the valves

 

[turbofabricator]

Even an umbrella or PC seal will do NOTHING on a STOCK exhaust valve. The undercut on the stem is WAY smaller than the ID of the seal. Aftermarket valves NEED a seal, though. http://images.gmhightechperformance.com/tech/0209gmhtp_buick11_zoom.jpg

 

[workingdan]

Thanks for all the advice. I changed out my intake seals, springs and made some soild rocker shafts. Cant wait to drive the car this spring. Damn michigan winters!