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Old 05-12-2022, 10:04 AM
djseth djseth is offline
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Default Valve Seals

Hi All,

Spring is here and the TA is out and about! Several projects will be address this year, including new Oil Seals on the valves. Everything is fresh on the motor and only about 1,000 miles on it. When I had the heads off I put the umbrella type seals on the valves and I think I did it wrong so there are puffs of the old blue at deceleration etc... The famous Nunzi Romano did all the machine work on my motor, one of the last ones he did, and something is nagging in the back of my mind that he grooved the valves to accept the better Chevy seals? Not even sure what I look for, but what to replace and get the right things. Any info/help would be most appreciated. In case it's not in my Sig, she is a 1970-1/2 Trans Am, Ram Air 3 motor. Thanks in advance!

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Old 05-12-2022, 10:10 AM
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Stuart Stuart is offline
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Nunzi's son is a member here - maybe you could contact him to get your question forwarded to his dad. Look for tommy67.

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Old 05-12-2022, 10:25 AM
djseth djseth is offline
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Amazing! Thank you so much for the help. Looking for him now.

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Old 05-12-2022, 10:29 AM
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John Milner John Milner is online now
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If there is a 2nd groove on the valve under where the valve retainer locks go, it is machined for the o-ring style seals. For an o-ring seal to work properly, you really need to be running the metal shields that go at the top of the spring and stock retainers if you use this style of seal. Your engine would have come with this style of seal from the factory. It sounds like you are running the Ford style umbrella seal that slips over the valve stem, some Chevys used them as well. The best option is probably the positive Viton oil seal that presses on the guide and fits tight over the valve guide. However, the heads would need to be machined for this type of seal. I would be willing to bet that Nunzi machined them for that style of seal. To verify, you can measure the top of your guide. It will likely be .500 or .530 in size if machined for this style of seal.

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Old 05-12-2022, 10:37 AM
djseth djseth is offline
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Quote:
Originally Posted by John Milner View Post
If there is a 2nd groove on the valve under where the valve retainer locks go, it is machined for the o-ring style seals. For an o-ring seal to work properly, you really need to be running the metal shields that go at the top of the spring and stock retainers if you use this style of seal. Your engine would have come with this style of seal from the factory. It sounds like you are running the Ford style umbrella seal that slips over the valve stem, some Chevys used them as well. The best option is probably the positive Viton oil seal that presses on the guide and fits tight over the valve guide. However, the heads would need to be machined for this type of seal. I would be willing to bet that Nunzi machined them for that style of seal. To verify, you can measure the top of your guide. It will likely be .500 or .530 in size if machined for this style of seal.
Hi John, thanks so much for the info. I will need to take the springs off obviously to see that I have. Since Nunzi's work, I have moved to a full hydraulic roller cam and lifters. I don't think the metal shields are on the springs now and not sure I have them, even though I am notorious for throwing away NOTHING to do with my TA! I put the butler umbrella seals on her when I did the cam. Do not know if it's machined or not though. But, she puffs blue on Reve and de-cel. I figured I ripped the seals when I installed. If I do have the groove, how do I find the right seals for that groove? Is there a standard?

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Old 05-12-2022, 12:06 PM
djseth djseth is offline
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Just had an additional thought. If I have the "tapered or bottle shaped springs" will the metal shields even work?

  #7  
Old 05-12-2022, 12:13 PM
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Half-Inch Stud Half-Inch Stud is offline
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The modern umbrella seals are dimeter specific for fit on .500" or .530" guides, and are tough to install. I ruined a bunch and had to buy more.

The ruin was due to the guides having an edge rather than a pleasant chamfer. The Seal is willing to shear inside, and bunch-up inside, such that the seal wants to pop-up right after the bad install.

Also there ought to be a tool, or instructions for how-to-install.

Meanwhile you can remove a valvecover and peek inside each spring to see if the seal popped-off and is riding with the valvestem. Had that puffy scene 25 years ago.

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Old 05-17-2022, 02:05 PM
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lust4speed lust4speed is offline
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Pontiac used no seal on the exhaust side and a black rubber seal on the intake - so if you see a seal on the exhaust guide then the guides have been cut for positive seals. In conjunction with the original Pontiac setup an O-ring on the valve stem was used just under the valve stem locks and the metal shield. This complete (archaic) system worked okay at best.

Really unfair to call the positive seals a "Chevy" seal since Viton seals were used on WWII aircraft long before the racing community found out how good they worked. I hate Teflon seals in that they pass more oil down the stem and from my experience they wear rather quickly. Viton is definitely the way to go, and when the guides are cut and Viton seals are installed the O-rings and metal shields need to go away since the Viton seals can be damaged with additional limiting of oil on the stem from the O-rings and shields.

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Old 05-18-2022, 08:08 AM
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viton since 1957, otherwise great post.

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Old 05-18-2022, 02:33 PM
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" Deceleration " this , IMHO, may end up being rings not seated properly.

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