View single post by Mark Rosenbaum
 Posted: 04-30-2005 11:57 pm
PM Quote Reply Full Topic
Mark Rosenbaum



Joined: 03-12-2005
Location: Kingman, Arizona USA
Posts: 532
Status: 
Offline
 Using a cam carrier as a holder, you could bolt a degree wheel to the front of the cam, then gin up a rigid fixture that would place a dial indicator's tip in contact with the cam lobe.  Rotate the cam and note the degree wheel marking when the dial indicator first rises to 0.050" above the heel of the cam, and when it drops to 0.050" on the other side of the lobe.  The cam duration is the difference between the two degree readings.  (Note that some cam manufacturers spec their cams at zero lift instead of 0.050" lift, and you can expect a difference of 20 to 30 degrees between measurements made at the two sets of points.)

Finally, since the cams turn at half the crankshaft rate, and everything automotive is based on crankshaft degrees, you would double whatever duration you get in this test before comparing your figures to the published ones.

Given the fact that there are so many different Lotus and JH cams around, I'd think it prudent for anyone building a performance engine to verify each cam's duration with a test of this sort.

Last edited on 04-30-2005 11:58 pm by Mark Rosenbaum