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272 11+mm lift, any drawbacks?


RB335
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Hi Guys.  

I'm putting together my 2.8 engine.  The exhaust will start off with a HKS 272 10.2mm lift.
Eventually I wanted to experiment going with very big lift, such as JUNS 272 which has 11.35mm lift.
I can only imagine to get that lift, the lobe will have a more agressive ramp and get more lift earlier in the duration.

This question is for exhaust only as I won't be playing around with the intake.

So far I had been under the impression high lift with same duration only ads benefits and no drawbacks.

Can anyone with experience with this add some input?

Edited by RB335
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Super high lift cams usually require clearancing of the bucket bores. This is a full head dismantlery exercise.

Super high lift cams put quite substantial demands on the valve springs. They need to be able to take the lift without binding and to control the movement of the valve over the nose of the cam. Granted, it's not so bad when it is just high light at low total duration as when it is both high lift and long duration.

Of potential interest is trying to get a cam profile with a really wide nose, to try to give the longest time at the highest lift. This will still give rather steep ramps (like a long duration cam would), but is probably worth it. But you would need/want to talk to a local supplier in Oz or NZ to discuss. You won't get it from those Jap cams.

Lighter valves worth thinking about for all the above reasons. Lighter retainers, etc also.

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