Question for Duke: L79 cam specs

[Gary B.]

Duke,





Are the 110 and 118 the degree numbers for the intake and exhaust, respectively? And is the L79 lobe separation angle of 114 degrees come from averaging 110 and 118?


Thanks,


Gary

[Duke W.]

Re: Question for Duke: L79 cam specs

Yes, I always list inlet/exhaust: .050" lifter rise duration/POMLs/LSA/lobe lifts

For for the L-79 cam:

222/222/110/118/114/.298/.298

I've seen both 221 and 222 published over the years, but after I obtained the detailed lobe data (lift in inches to five decimal places every cam degree) I came up with 222 rounded to the nearest degree.

In recent years I've recommended the L-46 cam for L-79 rebuilds:

224/224/114/114/.300/.306

but if should be installed advanced four degrees to bring the POMLs back to 110/118 for the shorter stroke 327. As you can see the inlet and exhaust specs are very close, but the lobes are actually differenmt. The reason I prefer the L-46 cam is its refined dynamics, and I believe different lobes were used with slightly different dynamics due to differences in inlet and exhaust valve weights.

And yes, the LSA is simply the arithmetic average of the two POMLs.

I use the term POML (point of maximum lift) because most Chevrolet cams have asymmetrical lobes. The closing is more gentle than the opening so the "centerline" is not the same as POML. Only the Duntov came has symmetrical lobes and they are the same on both sides other than the exhaust having .004" greater clearance ramp height.

Duke

[Gary B.]

Re: Question for Duke: L79 cam specs

Thanks Duke. Very clear explanation.

Gary