Some of you may remember I replaced my valve seals on my 327/300 plus motor last April. The worth of it is well known now. The motor has about 96K since the rebuild in '84 and I do rag on it. For about the last 10 years I would have had to put a qt in about every 500-600mi. Since my last oil change in late May I have put on 1478 miles and added one qt 10w40 GTX at 981 miles. I never realized how much oil was going out the pipes with the dried up and missing oil seals. If any of you are using oil and you have tested for good cylinder pressure, consider replacing the seals. Dennis

 

Which flavor of valve seals did you decide to use? I know there is lots of discussion about this topic. Thanks!

 

The best all around seal for most everyday operations will be one made of Viton. Many of the regular cam manufacturers offer them. Viton is a material that holds up best in the valve train environment and installs easily with typically no machining necessary. They're also very reasonably priced. Here are some Comp Cams ones that sell for $20 a set from Jegs.

"Viton seals provide better sealing to keep oil out of combustion chambers for improved engine efficiency and performance"

http://www.jegs.com/i/Comp-Cams/249/...ductId=1122701

Good luck... GUSTO

 

The basic small black o-ring style. They are easy to put on, and do the job. Maybe some guys can and like to use the umbrella style. Dennis

 

Thank you both for the info!

 

I put new seals on my BBC similar to those. However the exhaust only had umbrellas on them. I read somewhere later that those may not allow enough oil to lube the exhaust valves. TRUE or FALSE?

 

GM on later engines (such as the alum. head L98 - 1987 vintage) only used positive seals on the intakes (similar to those shown in Gusto14's post) and no seals on the exhaust (but both still had the square cut "O" ring seals at the top of the valve stems). The reasoning is that the intake guides / stems see intake vacuum when the intake valve is open, so it tends to draw too much oil down the guides (hence the need for either the positive seals or the umbrella seals), while the exhaust guides / stems see positive pressure (trying to blow the oil back out the top pf the guide) when the exhaust valve is open, and the exhausts run much hotter, and need more oiling (hence the reason for no seals).

To confuse matters, some engines still came from the factory with the positive seals on both the intake and exhaust valves, but I believe that these were the cast iron heads only.

Note that umbrella seals are not really seals (as used on some Ford engines and sold aftermarket for Chevy engines) that slip over the valve stems above the guide boss, and float with the valve as it goes up / down. They do not seal to the guide boss (as a positive seal does), but prevent most of the oil splash / mist from going down the guide / stem. They are more effective than just the square cut "O" ring that seals the valve stem to the valve retainer. However, if running the inner valve springs (dampers), they may not float due to interference with the damper spring (must be sized correctly - like everything else).

In your case (if in doubt), I would run extra seals on the intakes only, be it positive or properly fitted umbrella seals (along with the "O" ring seals on both valves). You may see a puff of smoke at startup, but that is a minimal price to pay (vs. having to replace guides and valves due to a lack of lube). And if you do see a puff, it might mean that the "O" ring seals are not doing their job or that the guides / stems are worn.

Plasticman