Overlap question
02-21-2005, 11:41 PM
#1
Staging Lane
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Overlap question Does anybody know of a way to convert Crane's Advertised duration at .004 to everybody elses advertised at .006?
I am trying to figure overlap on a few crane cams and compare them Comps and others.
The cam I am looking at from crane is
277 advertised and 216 at .050 intake
285 advertised and 224 at .050 exhaust.
Comes up with 51 deg overlap at .004
and -10 deg overlap at .050 with a 115 deg lobe sep angle.
I am looking at a Crower with
272 advertised and 217 at .050 intake
280 advertised and 226 at .050 exhaust
Comes up with 48 deg overlap at .006
and -6.5 deg overlap at .050 with a 114 deg lobe sep angle
And finally the Comp Cam
271 advertised and 218 at .050 intake
279 advertised and 226 at .050 exhaust
Comes up with 47 deg overlap at .006
and -6 deg overlap at .050 with a 114 deg lobe sep angle
As you can see, the last cam has the least overlap at .006 yet the most at .050.....
Not sure where to put the crane, because the figures are at .004 instead of .006.
Which overlap is more important to idle quality, at .050 or at .006/.004?
Thanks in advance....
I am trying to figure overlap on a few crane cams and compare them Comps and others.
The cam I am looking at from crane is
277 advertised and 216 at .050 intake
285 advertised and 224 at .050 exhaust.
Comes up with 51 deg overlap at .004
and -10 deg overlap at .050 with a 115 deg lobe sep angle.
I am looking at a Crower with
272 advertised and 217 at .050 intake
280 advertised and 226 at .050 exhaust
Comes up with 48 deg overlap at .006
and -6.5 deg overlap at .050 with a 114 deg lobe sep angle
And finally the Comp Cam
271 advertised and 218 at .050 intake
279 advertised and 226 at .050 exhaust
Comes up with 47 deg overlap at .006
and -6 deg overlap at .050 with a 114 deg lobe sep angle
As you can see, the last cam has the least overlap at .006 yet the most at .050.....
Not sure where to put the crane, because the figures are at .004 instead of .006.
Which overlap is more important to idle quality, at .050 or at .006/.004?
Thanks in advance....
02-22-2005, 12:15 AM
#2
Ah, this shows how important cam profiles are. I doubt there is much difference to worry about between .006 and .004 . . . ever seen how little two thosandths of an inch is? The comp cam is probably that way because it probably has more agressive ramps than the other cams.
I would just subtract 50 degrees from all of the cams with advertised durations and compare them all at 50 thou. Or call the cam makers and get the actual numbers at 50 thou.
I would just subtract 50 degrees from all of the cams with advertised durations and compare them all at 50 thou. Or call the cam makers and get the actual numbers at 50 thou.
02-22-2005, 08:20 AM
#3
Thing is that you can't convert the numbers over because of the ramp rates of the camshaft. You said that the Comp cam has the least overlap at .006" but the most at .050"...this doesn't make sense...all the at .050" overlap numbers are in the negative..so none of them have ANY overlap at .050". Just look at it in that sense.
