Originally Posted by Bored&Stroked (Post 2295829)

The original Potvin 425 Eliminator cams were usually done on billet steel 32 cores - with the bearing journals done to .010 undersize. The undersize journals were usually done because in 32 there were no cam bearings in the block - so the cam just ran on the cast iron. Due to this, an older cam might be worn a bit in the journals - so .010 made sense.

Given how small the base circle needed to be to achieve .425 lift, Potvin felt the 32 cores were better than cast cores.

> Actually the base circle of the 425 is very close to many of the popular
performance cams of the day. The main difference was the Potvin's were
"swept ground" instead of relieving the core. This was primarily a cost saving
operation. It has no affect on operation.

Also, some believed that the steel cam would last better than a cast one - as the Potvin 425 profile has a sort of "point" at the top. This is the only Potvin cam that has that lobe profile that I've seen.

I had a 425 that was ground by Bill Jenks at Moon - it was a cast core cam that had the tops of the lobes welded up. What I don't know is . . . was that done to achieve the lift needed, or was it done to make the top of the lobe last longer. I never had a chance to ask Bill the reason.

> I have redone quite a few of those cast original 425's and the discoloration
was heat treating, not welding.


I recently had "Pete" regrind a 32 core with the Potvin 425 profile. It still has the original "press on" type of gear on the front - which actually makes setting the cam timing easy.

Originally Posted by 3W Hank (Post 2295918)

Here is the cam I saw.
No marking on eliminator but surface is smaller, instead a ’E’.
Could it be a Potvin early 50’s or a copy.
I can’t say.

Originally Posted by 3W Hank (Post 2295918)

Here is the cam I saw.
No marking on eliminator but surface is smaller, instead a ’E’.
Could it be a Potvin early 50’s or a copy.
I can’t say.

Originally Posted by KiWinUS (Post 2295921)

Have you measured the lift? I have two originals and neither has .425” lift. I am led to believe none had exactly.425”.
I also have had a master made off one of my originals.

Originally Posted by 3W Hank (Post 2296059)

Got this cam in position, its straight and lift is around 424.
Cant see any issues but some tips has angle, se picture where screwdriver points, some is not.
Hard get a 32 core plus machining and a AB adapter.
If a old Chuck’s its cool to my car.
Will has it in a camdoktor.

Originally Posted by 3W Hank (Post 2296144)

Ah, so Jenk made cams so late.
Good info, did he mark the ’POTVIN’ ?
-Well my coupe is try be a time machine based on as much Henry and old speed parts as possible.
The cam I showed and asked history on, I has now.
I was kind of wanted a 32 core for several resons.
I was not really into a cast core but this got to be now.
I’m open on get a 32 cam ( original 40’s ) or grind a new aswell.

Originally Posted by 3W Hank (Post 2296198)

So from what you see this cam I show could be a Bill Jenk work sometimes in the past.
If so that is cool.
A question, you mention wide lobe 59BA, was that all 59AB or just some cams ?
If I grind one I has a very nice 59AB ( I can mesure lobe diameter ) but a odd thing on that cam is the all 3 journals is not 1.7955” but 1.7920” ( a odd number on undercut even from Ford, as I had heard on -0.002” )
The old Sweden hotrodder on the 50’s my guess used the 3/8 cams, not the 425.
Great to know history.
I read a book now on all the speed legends.
It’s a picture on Bill Jenks in his roadster under the chapter Chuck Potvin.
I also seen the ’Potvin roadster’ someone restored.