[4bangerbob]

I am planning on running OHV heads on the burtz block kits I have purchased. As the rocker arm ratios are 1.5 to 1 using the standard Burtz camshaft with .340” lift would result in too much lift when using the OHV heads. While I thought of using a standard lift model A camshaft I did not want to loose the support offered by the 5 cam bearings that are in the burtz block.

Thus I decided to purchase a couple of camshafts from the burtz group and upon conferring with Terry and determining that there should be sufficient hardness at the resultant lobe configuration after grinding.

I sent the burtz cams and had Jim Brierly grind the camshafts one to his M-58 grind and the other to his M21 grind (specification shown below).

Once I got the cams back, I went and got the camshafts checked for hardness. I had them checked using Ultrasonic Contact Impedance (UCI) method so as to leave no marking on the surface. We wet sanded the nitrite coating off in an area on the lobe where the camshaft is allowing the valve to lower back onto the seat. The testing was done on four lobes total, two on each camshaft. The hardness found ranged from 55 - 57 Rc mid lobe to 59 - 62 Rc near the top of the lobe. So I think the cams should be good for some time. The Burtz spec for the lobe hardness as supplied is 58-62 Rockwell C ranging from 3mm (at maximum lobe lift) to 1.5mm (at cam base diameter).

No. Duration Lift (gross) Clearance
at cam at valve
in. exh.
M-58 280 .295 .444 .010 .015 fair idle, good street

M-21 286 .298 .448 .018 .020 hot street cam


I have attached a copy of the report as issued by Nortech (the company that performed the testing) and another file showing the cams and the areas where the testing was done. There were approximately 10-15 tests done on each lobe section and then the findings were averaged. I can also note that before the nitride coating was removed the readings were lower, about 10-20 points lower, so if someone else tests they should be aware to be testing on base material.