The V8 Owners Forum -

Just got my 4.6 up and running. spec is. 10.8:1 CR Mechanical 238 cam 512 lift, Yella terra roller rockers.
The spec sheet for the cam says 22 thou valve clearance Hot.
This seems quite a lot, am I just losing 22 thou of lift ?
Is it safe to reduce the clearance to say 15 thou.

Thanks

Mark

Hi 20 to 22 thou valve clearance is the normal range, the cam is intended to run at this, you can tighten it to about 18 thou may be even 16 thou hot but you will increase the duration of each lobe.
It is a good way of finding out if you have the right cam for the combination of heads etc, tighten the valve clearance a bit and it produces more power over a wider rev range you need a cam with more duration. Open the valve clearance a bit and the power increases then you need a shorter duration or wider LSA on the cam.
Mike

I've got a big solid crower cam and the card says to run .022 hot on inlet and .024 hot on exhaust so it looks like the cam manufacturers are in agreement on this.

Thanks guys, big learning curve.