Valve protusion/Installed height

[Steve Little]

Hi.
Over the years I have worked on quite a few Pan heads.
I have noticed that a lot have had the valves cut too deep into the seat, and as a result, the upper valve spring collar collides with the tin or stainless valve covers. At the moment I can’t remember if the alloy covers are affected in the same way (memory must be defragging) but I would guess they do.
I have collected a few original metal covers and most have witness marks from the upper collar striking them. Some previous owners have beaten clearance into the area, which distorts the gasket area and makes the D ring hard to get on or off.
I have one cover that has Taiwan stamped inside and after a quick test with a valve and collar, it has less room than an original.

There is no “Installed height” listed in the Genuine HD service manual, so I’m hoping some members may have experimented and written down some measurements from NOS heads.
Or perhaps the maximum installed height before an original collar will strike an original cover.

The reason for my inquiry is that I have a set of 1950 heads that need new seats and before giving them to the guy who does the work, I would like to take the correct information when I drop the heads off.
Regards Steve

[MMasa]

Steve
You may want to check with Don Sullivan at Head Hog. Pretty much all he does is Panhead and a little Knucklehead head repair. Www.headhog.com
He should be able to answer your question. He can also do the repairs if you like. He does not "replace" the worn seats, but instead does a weld overlay to build them back up and then re-machines them to stock. He's not fast but that's mostly because so many people use him and the que is always quite full. He is however a perfectionist. He's done a few sets of heads for me and they looked NOS when I got them back.
Mark

[jstraker]

Lee Wickstrom of Lee's Speed Shop in MN also wrote about this recently on his blog. You might want to check that out (http://knuckleheadtheology.blogspot....-pans-and.html), and/or follow up with Lee. You can find his contact info if you Google his shop.

Cheers!

Justin

[T. Cotten]

Steve!

Its in the later manual.
The solution is oversized valves.

....Cotten
PS: Hardened seat replacement has trashed more Pan heads than they have saved!
If you MUST replace a seat, please find OEM bronze.

[Steve Little]

Thanks to all.
Cotton's factory image showed me that the info is in the service manual.
Page 75 in the 48-57 manual, and page 3B-3 in the 59-59 manual.
I had confined my search to the "Engine Specification" page at the start of the engine section.
Thanks again.
Steve

[jorrow]

Would those specs also apply to Knuckle?

[T. Cotten]

Jorrow!

I have been away from motorwork for many years, but I do remember Knucks had much shorter valvestems.
It would take comparisons of NOS spring installed heights and other things to even guess, as if such hardware still exists. No matter what, each assembly requires careful inspection of spring spacing, free travel, rockerarm geometry, etc.

(You can grind the tips of the stems to help rockerarm geometry, but that will not help interference of the collars and covers.
But then collars can be shaved as well. The hard part is measuring clearances that might as well be at the bottom of a well.
Even using modelling clay or Play-Doh is difficult and tedious.)

...Cotten