[dhcarguy]

I do not understand cams numbers (duration and lift) and how they compare with performance. How does my cam compare to a Pontiac stock cam. Like maybe a Ram Air IV???

Thanks, Dave

[25stevem]

Well first off your Cam is what's called a single pattern Cam because the Intake and Exh duration numbers are both the same.

In comparison to a RA4 Cam yours has 10 degrees less Exh duration @ .050", it also has .009" less lift at the valve with a 1.50 rocker then a RA4 Cam which would have .469" lift with a 1.5 rocker.

In general the ago old saying that duration is what makes for peak hp taking place, and the amount of valve lift making Torque still is applicable to any engine.

[dhcarguy]

Ty Steve

[25stevem]

Ps.
The production of added torque by means of increasing valve lift hinges greatly on the intake port and the whole intake side flow system having untapped high lift air flow available to be used.

[PAUL K]

We have used that Lunati grind many times in the past. It works great in a 455 street car build. Compared to the RAIV it will have more mid-range snap. Idle quality is similar and it will work okay with a stock torque converter.

This is a thread for a 455 we built using that cam:

https://forums.maxperformanceinc.com...errerid=134156

[turbo69bird]

Over simplified -

Duration is amount of time it’s off it’s seat.
Lift is how high it’s off its seat

The two combined is area under the curve this affects how much air can get in or out.
LSA is number for overlap of valves which can be used to scavenge during use naturally aspirated usually a smaller number
And for boosted it’s usually larger number.


Think of it as a tire gong over a bump. Duration is how long your on the bump.
Lift is how high the bump is…