Cam Heel Grinding?

I ran a search but couldn't find anything about grinding the lobe heel of a cam to get more lift. I heard guys in the fifty's did this! You don't have to worry about the losing the hardness because the heel is where the clearance is located.
What I wondered about was, did they just grind it freehand on a grinder or sit up a jig to try to do it with any accuracy at all? I thought that it might be fun to try on a small motorcycle engine that I have that there is no compe***ion parts available for.
Has anyone ever heard of this or can direct me to someone who does? Thanks, Gene

 

ummm think about this for a minute...if your cam is shiney where you are considering hitting it with the disc grinder...it means that the follower will be riding there too. so if you take the hardface off,it will wear most dramatically.

 

That is where your clearance is!!!

 

I was reading some Navarro info the other night. He was not a fan of it in flatheads because the cam flexed under high RPM, due to less material in the heel. He avocated grinding a larger cam to tstart then work back to the desired grind.

 

Regrinding the base circle to get more lift was common,
especially on oddball motors.

But it's not something the average guy is going to do at home.

 

Lots of guys did it back in the olde days.
We called them belly grinds.
You braced it against your belly while pushing it into the grinding wheel. Surprisingly some worked very well.

 

Belly grinds had a nice lopey idle didn't they Pete?

Actually, since you are a cam guru, if you were to take .020" - .030" off of the heal on a typical 325" lift cam, how much does that affect the duration? And am I correct in thinking it increases the duration?

 

Did this for years in stock car racing. When they put a mic on the cam it would show under and they would past me. Thought I was the only one that did this.

 

I did it to a little Briggs one banger when I was a kid. Had to spin it with another motor to get it started, but it really wailed when it ran! It was on a minibike.

 

As I understand it, that's pretty much how regrind cams get reground. Grind down the base and the lift from base becomes greater. Can't remove material from the lobe peak and gain lift. Comes out nicer on a cam grinder then it will on the Craftsman bench grinder.

 

Designing your own cam on a bench grinder.......surely better than something an Engineer could design

That it works once in a while, just goes to prove, luck IS better than skill !!

 

Brent:
Yes it does increase the duration..How much, is guess work.

 

I done Briggs and lauson cams this way for 1/4 midget racing.
I used a spin fixture with a collet chuck to hold the cam. set it up on a bridgeport and milled away while slowly turning the cam thru the base. Those cams are soft enough to mill. This way you got a lot of control on how much depth you take off and how much arc you turn.

I also did a few by welding up the lobe part, adding height, and then milling by using the cam profile dimentions and degrees to adjust the mill , and then filling the ridges away and polishing. It worked but i had more time (then brains) to play around then.

If your only doing a mcycle, one or two cylinders, go for it by hand and a micrometer.

Frank

 

"And am I correct in thinking it increases the duration?"

If you want, just stop undercutting the base circle short of the ramps.
If not, duration is same.
If you cut into the ramps it's reduced.