[ekancler]

In a recent thread on cams it was pointed at that Pontiac measured intake seat duration at .002" and exhaust seat duration at .008". (Post #38 Ken Crocie): https://forums.maxperformanceinc.com...ne+lift&page=2

Seems to me this is important information when considering making a change from an OEM cam to an aftermarket cam. And that rating dual pattern cams this way would tend to underestimate the differences between intake and exhaust seat durations.

Stan Weiss provided the following data later on in the thread I think for the 744 cam:

CAM_______Lift______Opens___Closes__Duration
________________Deg_BTDC__Deg_ABDC_______Area____I CL
_________0.00200____33.46_|__91.59_|_305.05_|__21. 91_|_119.06
_________0.00300____31.11_|__87.97_|_299.07_|__21. 90_|_118.43
_________0.00400____29.17_|__84.89_|_294.07_|__21. 89_|_117.86
_________0.00500____27.50_|__82.28_|_289.78_|__21. 88_|_117.39
_________0.00600____26.00_|__80.00_|_286.00_|__21. 88_|_117.00
_________0.01000____21.16_|__73.10_|_274.27_|__21. 83_|_115.97

So... If I have a Pontiac cam with intake/exhaust seat duration rated at 301/313 (744 cam) and I want to "convert" those to .004" for the sake of better comparing to an aftermarket cam, the intake duration will decrease, perhaps to 292, and the exhaust duration will increase, perhaps to (if the lobe profile is similar) 325.

Am I thinking about this correctly??

[Stan Weiss]

Maybe Ken will see this thread and post.

I took what Ken said to mean that instead of measuring seat duration at the same lifter raise on both sides of the Lobe. That Pontiac used 0.002" on the opening side and 0.008" on the closing side of the lobe.

Stan

[ekancler]

Originally Posted by Stan Weiss

Maybe Ken will see this thread and post.

I took what Ken said to mean that instead of measuring seat duration at the same lifter raise on both sides of the Lobe. That Pontiac used 0.002" on the opening side and 0.008" on the closing side of the lobe.

Stan

Well shoot. Re-reading that post I think you're right.

[KEN CROCIE]

The 744 cam: Cam Doc sez---301.8 intake / 312.8 exhaust @.004 " lift.
I haven't forgotten you, Steve !