How not to regrind a camshaft.

[@DaveMcLain]

Your cam will have infinite jerk wherever there is a discontinuity from base circle to flank and flank to nose radius without doing some smoothing. In the old days cams were often modified just like this, smoothed by hand and then used as a model to make a new master for grinding cams with different characteristics.

[@1magnit]

I think I did a 3 angle smoothing either side of peak lift and then rounded it with the crank polisher. Also a mid cut where it comes off the base circle where the flat part meets the existing ramps, again smoothed with the crank polisher. But anyway it's in the car and running for over a year now, on another vid.

[@DaveMcLain]

@@1magnit If the valvetrain is light and stiff enough and the rpm isn't too high you can get away with a lot without causing too much trouble. It would be interesting to do a plot of the profile.

[@1magnit]

@@DaveMcLain I've done that, there's a difference of about 8 degrees between the front and rear cams due to the finger followers. That's WHY I made my own because none of the off the shelf aftermarket cams are ground correctly.

[@1magnit]

kzbin.info/www/bejne/ammqgaaXfNiIla8

[@1magnit]

I set up the cam with peak lift referenced as zero deg. Then Zerod the runout at the bearings, then plotted with the dial gauge lift vs degrees Starting at the base circle then 0.02 mm, 0,05 mm0.1 mm 0.5 mm 1 mm, then 0,5 steps up to peak, then the same going down to closed. I did that on every lobe with all 4 cams (before as well as after). I also plotted the lift at 0.050 inch on the cam as well as what we should see at the valve, for comparison with other cams. The finger followers on the front bank are reversed compared to the rear bank, The rocker ratio isn't a fixed number, it changes with lift. It's the changes to the ratio as the valves lift that requires the front and rear banks to have different profiles at the cam in order to give the same lift specs at the valve. The difference is 8 degrees ,If you've fitted incorrectly modified cams to your 6G then you'll know when you set them up measuring the opening and closing at 0.050 inch and then you go and measure where peak lift is, both banks should be the same.