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Old 01-05-2009, 04:21 PM
oldbogie oldbogie is online now
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Quote:
Originally Posted by maxpower_454
I am rebuilding a set of 461 double hump chevy heads and bought umbrella valve seals to put on. I went to install them and it turns out that they fit the valves but hit then the valve springs will not fit over them. They hit the damper. Any idea why? Did i get the wrong ones? These are for a 327 and I think that is the engine these originally came on.
Not an unusual problem, I'd keep the dampers they do a decent job of calming the spring's harmonics. The usual process is to trim the umbrella seal till it fits inside the spring assembly. They aren't really seals in the sense of Perfect Circle Teflon seals in that they never prevent oil from entering the stem to guide clearance. All an umbrella seal ever does is to redirect oil off the stem so that the stem/guide interface isn't swimming in oil. Many Chevy engines just use an O ring that rides on the stem, how's that for a minimalist approach.

The biggest oiling problem is on the intakes since the bottom of the stem/guide is in the intake and is subjected to manifold vacuum which tends to pull oil down the guide. So keeping the intakes dryer is the problem.

You should have really put positive seals on there which requires machining the top of the guide for installation. They are really the only effective way of controlling oil in the stem/guide interface, umbrella seals and O rings are not all that effective, they just meet the production requirement of cheap and generally last long enough to get the engine to the end of the warranty period.

Bogie
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