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Camshaft lift vs duration independently

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Hi all,

I'm in the process of planning a head package upgrade on a 1jz non vvti, and whilst during the check of camshaft specifications came across something I can't really find a clear answer for.

Comparing the Brian Crower 264 degree (BC0331) and Kelford 260 degree (229-B) options, which are measured in thou and mm respectively, the main difference I see is lift. As those cams are either at 218°@50thou for BC and 222°@39.4thou for Kelford there is a small duration change but what I see looks consistant and pretty close for the 10.6thou measurement difference. The biggest difference is 8.74mm lift and 9.6mm lift and so I'm curious where the difference would be between these.

How does lift vs duration affect the engines VE? With all things being equal and simply a change in lift what would you expect to see in terms of a VE change? I would imagine that the peak torque would increase over most of the rpm range as it could more efficiently fill the cylinders?

Compared to identical lift cams but one has more duration, would this push peak torque and VE higher in the rpm range?

I hope this is clear and makes sense. I would really like to know more about camshaft design and effects of the differences.



I think your answers will come from engine simulation. You might want to check out Desktop Dyno software:


Usually, you'd be correct in that shorter duration and higher lift is biased towards lower rpm, with longer duration with (maybe) less comparable lift biased towards higher rpm, but there is a third factor to consider and that is the opening and closing points of the camshafts which also, incidentally, affects the angle between the intake and exhaust centrelines and overlap.

With some engines there may be limitations on the breathing of the intake or exhaust ports, too, so additional lift may not have as much affect as additional duration, even at relatively low rpm.

Also, there is the follower design and diameter - with flat tappet/followers, there is a limit to the lift than can be used before the lobes run off the edge of the follower and/or the thrust angles and forces risk excessive loads on the interface between the lobes and the follower. This is a big factor in the use of roller followers on pushrod engines and the use of various designs of rocker followers even on overhead camshaft engines.

From my experience it has also something to do with the intended level of boost. Engines with very high boost like high lift cams regardless of duration.