Reading Cam Specs.. 50 or 53 degrees

[GIBSON]

Can someone please explain why there are 2 different positions on the duration when cam specs are written?

My need to know is because I had a cam built for my 93" shovel project where I wanted basically the same profile as an Andrews 'B' grind but for a .501" lift instead of .485".

The 'B' grind duration is labeled as '258' @ .053
My new cam is marked as '238' @ .050

Can that be translated to .053????

Such a low duration would be very prone to serious detonation wouldn't it??? Engine compression is 9.5:1 and I'm pursuing more torque than top end.

Thanks.

Thanks

[arealinvestor]

Originally Posted by GIBSON

Can someone please explain why there are 2 different positions on the duration when cam specs are written?

My need to know is because I had a cam built for my 93" shovel project where I wanted basically the same profile as an Andrews 'B' grind but for a .501" lift instead of .485".

The 'B' grind duration is labeled as '258' @ .053
My new cam is marked as '238' @ .050

Can that be translated to .053????

Such a low duration would be very prone to serious detonation wouldn't it??? Engine compression is 9.5:1 and I'm pursuing more torque than top end.

Thanks.

Thanks

238 is a very quick duration.The lift you have is .501.Your cam would probably be considered a bolt in cam.Detonation problems occur as a result of an over compressed mixture.It's not really your duration that you have to worry about.It's the intake close & your corrected comp.When you running alot of comp with to early of a intake close that causes detonation!!!!!!! At 9.5 comp anything running more than a 30 intake close should be fine!!!!!

[jerry34208]

This is great stuff:
http://www.v-twinforum.com/forums/v-...questions.html
BTW the diff between .050" & .053" is 3/1000 of an inch. Not significant in this situation.