Difference in valve seals? - Chevelle Tech
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post #1 of 8 (permalink) Old Apr 20th, 03, 12:41 AM Thread Starter
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I'm just wondering what the heck is the difference between all the different kind of valve seals(umbrella, viton, teflon, PC????).

I have a set of World S/R heads that I am about to take off to port and from what I have heard they have quality control problems on oil getting past the guides. What kinda seals do these things have stock and what should I go to to fix this problem? I don't have any smoke coming from the pipes but I do get a little oil on the plugs and I doubt it is the rings(engine has been doing this as long as I have it and I got it with 500miles on it, built by a pro shop). I just wanna take care of this problem before it gets worse and while I have the heads off.

I heard I should try PC seals but then another person said they would not provide enough lubrication for the cast guides?! Anyone care to spread light on this for me?

Also how do I go about installing the new seals? Any tips?
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post #2 of 8 (permalink) Old Apr 20th, 03, 1:46 AM
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I have been told that umbrella and PC seals are good for the World Products heads. I used teflon seals on my Sportsman IIs, big no-no, so I get to remove them. Yay me!
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post #3 of 8 (permalink) Old Apr 21st, 03, 3:11 PM
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Allgo,
PC is a brand name, it stands for Perfect Circle, which is a division of Dana Corporation. PC is a manufacturer of valve stem seals for OE as well as the aftermatket. All types of seals are available from PC as O-ring type, Shedder (umbrella) and positive seals. Many materials are uses including Nitrile, Silicone, Nylon, Polyacrylic, Flourelastomer and Teflon. For most replacement seals, you are limited to O-ring or umbrella type with stock valve guides/castings.

Heads can be machined for positive seals and this is by far the best way to go for high performance engines. PC positive seals are available in three materials: Flourelastomer, Teflon/rubber and all Teflon. I personally use teflon seals for all performance and racing engines that I build. The teflon seals are smaller diameter and will fit with most dual and triple spring set-ups.

There is some misinformation out there, that teflon seals will dry up the guides/stems and cause galling. This is the case ONLY if the stem/guide clearance is too tight. If you look at a PC Teflon seal, the stem hole is very slightly chamfered, which draws an minute amount of oil each time the valve opens. Some competitive Teflon seals have a very shape edge on the stem hole, therefore they do not meter oil as the PC seals do. All PC TEFLON seals are white in color!!

As far as clearances, I always ream the valve guides to the middle of the recommended spec range for bronze and manganese-bronze guides and the high end of the spec for cast iron guides. In order for these clearances to be done correctly, it involves much more machinist's time and the investment in much more tooling (reamers). Also, I use a different reamer for bronze type guides than for cast iron.

Bill
64 Chevelle Malibu Sport Coupe (original owner) car now has 427" BB, Jerico 5-spd. trans., Dana 60 rear end.

SAE Member (25+ years)
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post #4 of 8 (permalink) Old Apr 21st, 03, 3:36 PM
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Currently, you are not limited to umbrella and o-ring seals for a replacement.

Now, Fel-Pro makes an excellent viton positive seal that fits over the stock guide boss. They run about $12 for a set of 8. I am currently running them on my mild 350 in my '86 C10. Have had excellent results so far.

Matt Jones
Mech Engineer, Art Morrison Ent.
1969 Base Camaro
LS1, C5 IFS, 14" 6-Piston/13" 4-Piston Wilwoods
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post #5 of 8 (permalink) Old Apr 21st, 03, 5:19 PM Thread Starter
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Silver69camaro- How do you go about installing them?
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post #6 of 8 (permalink) Old Apr 22nd, 03, 7:15 PM Thread Starter
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I also can't seem to find them in any catalog? Do you have a part number?thanks!
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post #7 of 8 (permalink) Old Apr 24th, 03, 12:44 AM
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Sorry for the late reply.

I just installed them as normal. Just press them on. They take a little work as they are supposed to be able to hold themselves on the guide boss during the valve motions. Instructions are included, but only tell you to use the plastic deal on the valve stem when installing the seal.

The Fel Pro part number is 'SS 725527', there is 8 included for all the intake valves, and runs about $12.99. I used umbrella seals for the exhaust.

Matt Jones
Mech Engineer, Art Morrison Ent.
1969 Base Camaro
LS1, C5 IFS, 14" 6-Piston/13" 4-Piston Wilwoods
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post #8 of 8 (permalink) Old May 5th, 04, 6:22 PM
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Quote:
Originally posted by Silver69Camaro:
The Fel Pro part number is 'SS 725527', there is 8 included for all the intake valves, and runs about $12.99.
My counter person thinks that there's a digit too many, as he can't find this number in their system. Any chance of double checking that number you posted?
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