The Ford Barn - View Single Post - Ford Model A Camshaft Inspection and Evaluation

Jim Brierley · 12-01-2020, 01:55 PM

I thought this was supposed to be about camshafts, not a critique on the video???
My evaluation of the pictured cam is that the lobes are very regrindable, if there is such a word? The minor pitting of the lobes will easily be removed while re-grinding the cam. A more important thing is the diameter of the center lobe, this is the one most likely to have wear. Questions asked by MikeK are:
1) How much measured wear is on each bearing journal?
2) How much bend/ runout when the first and last bearing are on V blocks?
3) How much wear is in the dizzy drive helix and is it even?
4) With a degree wheel and indicator do all intake & exhaust profiles match each other and are they index-timed correctly?

My answers are:
#1, I recommend a minimum diameter of 1.556".
#2, a cam is very unlikely to be bent unless it has been hit by a broken rod.
#3, very important, but oversize dist drive gears are available
#4, Extremely unlikely to be off.

In re-grinding a cam, the process is 1, straighten the cam. 2, grind the lobes, using #1 lobe as the starting/locating point. 3, re-straighten the cam. Often grinders then put a coating on the cam to lessen any chance of wear on break-in.

When I grind a cam I first machine the nose where the thrust button contacts it, if needed and almost always is. Second is re-machining the cam where the gear mounts, if needed, they are occasionally nicked or shows signs of mis-treatment. Third is to check the fit of the dowell pins, usually OK unless a pin is missing. I occasionally need to machine a pin that is larger in diameter than stock. When I make a new pin, I also make it longer than stock, for more stability. BTW, all pins are not the same diameter where they press into the cam. Note: Not all cam nuts are identical in thread diameter, I try to send the original nut with the cam I have re-ground, when possible.

Model A/B cams are made of very good steel, and do not require heat treating.

12-01-2020, 01:55 PM	#20
Jim Brierley Senior Member Join Date: Jun 2010 Location: Temecula, CA Posts: 4,088	Re: Ford Model A Camshaft Inspection and Evaluation I thought this was supposed to be about camshafts, not a critique on the video??? My evaluation of the pictured cam is that the lobes are very regrindable, if there is such a word? The minor pitting of the lobes will easily be removed while re-grinding the cam. A more important thing is the diameter of the center lobe, this is the one most likely to have wear. Questions asked by MikeK are: 1) How much measured wear is on each bearing journal? 2) How much bend/ runout when the first and last bearing are on V blocks? 3) How much wear is in the dizzy drive helix and is it even? 4) With a degree wheel and indicator do all intake & exhaust profiles match each other and are they index-timed correctly? My answers are: #1, I recommend a minimum diameter of 1.556". #2, a cam is very unlikely to be bent unless it has been hit by a broken rod. #3, very important, but oversize dist drive gears are available #4, Extremely unlikely to be off. In re-grinding a cam, the process is 1, straighten the cam. 2, grind the lobes, using #1 lobe as the starting/locating point. 3, re-straighten the cam. Often grinders then put a coating on the cam to lessen any chance of wear on break-in. When I grind a cam I first machine the nose where the thrust button contacts it, if needed and almost always is. Second is re-machining the cam where the gear mounts, if needed, they are occasionally nicked or shows signs of mis-treatment. Third is to check the fit of the dowell pins, usually OK unless a pin is missing. I occasionally need to machine a pin that is larger in diameter than stock. When I make a new pin, I also make it longer than stock, for more stability. BTW, all pins are not the same diameter where they press into the cam. Note: Not all cam nuts are identical in thread diameter, I try to send the original nut with the cam I have re-ground, when possible. Model A/B cams are made of very good steel, and do not require heat treating.