john73bb

I bought some teflon valve seals, and then found that they don't fit without doing some machining to the heads. Is that correct?

Several of my old umbrella seals were cracked at the top after only 5K miles. Should they be? What should I use for valve seals? Are some brands better than others?

Thanks,

John.

gearheadz

Teflon seals require the top of the guides to be machined down to fit. I went with the Viton rubber seals that are longer wearing than the Teflons, particularly on the street.

Mark

73 LS-4

Let us know what you go with John, I'm going to have this same project shortly, i think I have 3 seals leaking on mine, at least I'm finding oil on 3 cylinders albeit it doesn't burn much and I onlu occasionally see a puff on startup and nobody has seen a puff while hard on the throttle so everything points to the valve seals.

:cheers:
Pat Kunz

john73bb

mdsmith,

Are the Viton seals umbrella style or do the heads need dto be machined for them too?

mountainmotor

Some of the springs depending on the inside diameter of the spring will catch and lift the Vitons seals.The ticket for long life with a PC seal is to gently run a 3/8 drill bit through them to size them up a bit for less friction and a little more oiling of the valve stem.A 3/8 reamer by hand will work also.The key word is gently

Paul L

I have been told that for SBs, these work well. Have not tried them yet.

bence13_33

Could someone explain to me what a PC seal is? Is that a teflon seal?

I am going through the same thing right now with the big block. I will not be able to use umbrella seals with my double valve springs so it looks like my heads are going back to the machine shop to be fitted for teflon seals. :(

Rowdy Rat

Politically Correct seals... Nah, that can't be it... :)

Actually it refers to Perfect Circle which if I'm not mistaken, supplied the original teflon seals.

Take Mark's advice... Use the viton seals. The valve guides still need to be machined like the teflon guides, but they provide superior oil control compared to the teflon seals (especially for a street driven vehicle).

These viton seals are available from several aftermarket suppliers as well as GM... I believe that Joe Lucia posted the GM part numbers at one time on this forum. You might want to check the archives.

Good luck with your decision!

Regards,

john73bb

Does anyone know about what it costs to get the macining done for the Viton seals?

mountainmotor

$35.00 bucks usually 16 bucks for the seals.A good deal for the long life.
John, they truly are the ultimate if worked as I decribed above.I have built many ,many motors and would put these on moms station wagon with out hesitation

Paul L

When ordering stem seals, what is the diameter of the valve stem?

john73bb

I was told that in the old days (70s) that often seals came with a tool to hand machine the engine to take the seal. The tool simply had a rod to go down in the valve guide, and a cutter to cut to the proper depth for the seal. The person who told me this said he had gottem then with seals for Fords, not Chevys, but I assume the principle is the same. Is there such a device available today?

Phlash

You can get the viton umbrella seals. These work very well, never harden and crack. If you try to use the seals requiring the guides to be machined, make sure your guides don't have any slop (wear) in them, otherwise you will be replacing them in about 5k miles.

Phlash 72 BB Roadster :seeya

RatRacer

Pioneer makes a number PC (positive control) seals that do not require machining of the valve guide of big block chevy heads.

Paul L

So are there viton seals that do not require machining?

RatRacer

The Pioneer PC seals come in all rubber or rubber with teflon wipers. Neither require machining of the guides.

bence13_33

Cam:
Where can these seals be purchased? Will they work with my double valve springs? I can't use umbrella seals because of the double valve spring.

RatRacer

I got them from my machinist.

Paul L

We are back to PC vs umbrella vs positive poly vs viton vs fluoro vs teflon vs seating vs non-seating vs machining vs non-machining .... ;) Is there a viton seal set for a SB that is a positive seal that does not require machining? If yes, where might I obtain a set? Many thanks.

Phlash

Yes there is a viton umbrella seal (I think the last set I used were for a small block Ford). Best thing to do is to go to a reputable machine shop and ask them if they carry them. Take one of your springs if you can. I am not sure it is a stock chevy item, but you machinest can tell you what applications can be used.

Phlash 72 BB Roadster :seeya