Machining Valve Guides-Viton Stem Seals

[GOSFAST]

Below is a photo showing the machining dimensions we follow for setting up the bronze-lined (or conventional) Flathead guides to accept the "Viton" valve stem seals.

This post is in response to a PM request!

Thanks, Gary in N.Y.

P.S. We have a "dedicated" piloted seal-cutter just for this procedure, machines the correct O.D. and depth in single step.

[Pete F]

My only question is will the guides be to dry.
With the valve being upside down the oil has to get sucked in and I don't know if the seals will wipe to much oil off the valve .
So time will tell.
But I like the idea.
Keep us posted

[Lawrie]

Look at any modern engine,they all have seals.
Lawrie

[tubman]

Are these for the intake valves only like the stock seals?

[flatheadmurre]

Originally Posted by Lawrie

Look at any modern engine,they all have seals.
Lawrie

The big difference is that in an OHV gravity is bringing oil into the guide and some oil is always going past the seal.
Putting a seal on the exhaust of a flathead seems like a bit of trying to improve whats already working fine.
On the intake it should make some difference.
Putting in a bronzeliner with a honed surface and correct size on the intake will go a long way in oilcontrol...

[GOSFAST]

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Just to be clear, this is NOT a mandatory procedure, but I do have numerous customers asking us for it.

The intake "sees" vacuum which is why we normally prep them only. With the "Viton" seal material it will not "dry-out" the guides.

These are one of the few seals that don't require a "sleeve" to install them unlike the "Teflon" stem seals which we also still use. You simply push these seals onto the guide first (after machining it to the correct size/don't forget to pre-oil the stems also) then slide the valve into position. It will NOT "ruin" the seal going in, having said that they CANNOT be pulled back out however, this MAY and probably will do damage to the seal.

Thanks, Gary in N.Y.

P.S. This operation is considered a "customer choice" here, over the years we have built many without any stem seals and have not seen any real adverse effects. We do feel this is now a "positive" though when building these Flatheads.

[Ol' Ron]

Installing the guides with out the notch in the guide makes a simple operation wuite difficult, but it is a good idea. However Knurling the stock guide and reaming it for .0005/.001" stem to guide clearance will provide a great sea, well lubricated valve stem and very low cost. I've been doing this to all my engines for the past 30 years. I think sometimes we have a tendency to over design

[Kahuna]

I have used these seals on 2 flathead engines:
I machined the guides as Goesfast, then knurled
the outside of the guides to provide a
press fit into the bore. I also trimmed .100" from
the top of each guide keeping the same angle on
top. I then used Loctite "Sleeve Retainer" to keep
them in place.
I did this to be able to do some porting work &
not worry about the guides moving around.
No problems & those guides aren't going anywhere.

[Lawrie]

Ron, I made a simple bar with a curve on it to install the inlet guides that had the seals fitted and thus no groove for the fork to pull them down to fit the c clip.I just put the curved bar into the port and push down then guide assy with the springs and keeper already fitted then just slip the c clip in like normal.
Lawrie

[Cheaterpete]

Some French flathead got this modification from factory