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Discussion Starter · #1 ·
One of the things I do not see on Cam Specs any more is OVERLAP. How do you determine OL with teh information given on lift, duration ahd LDA?


Discussion Starter · #2 ·
generally, at 0.050 duration numbers there will be almost no overlap. (more accurately, there will be no way to measure it from those numbers without guessing at the lobe ramp duration) You need the advertised duration to get a more reasonable number. If you have the advertised duration, Take both intake and exhaust duration . Add them together and subtract lsa (ignoring any advance ground in), then divide by 8.

(edit: changed my formula, was in error before)

That should get you in the ballpark.

At least that is how I understand it. Hopefully, I will be corrected if I am wrong.

Discussion Starter · #3 ·
Most cam cards have the opening and closing times, if you add the int open and exh close times you will get the overlap. This only works if the times are listed as advertised (.006) not .050. will not work for .050. Comp cams lists these events at .006 on most of their cam cards.

If you have the advertised duration numbers and know the LSA use this formula:
Add the Intake and Exhaust adv durations
Divide the results by 4
Subtract the LSA
Multiply the results by 2

Here is an example using a XE268H:
Overlap is 54
Hope that helps.......
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