Cam Requirements for 3.4

[BillS]

All pivoted rockers, by their nature produce some side thrust in the valve stem.

They usually start a little past centre and as they open the valve the pivot and pull back, bearing more on the rocker side of the valve stem. This slight pushing side to side increases guide wear

You can substantially reduce (but not eliminate) side thrust by using a roller tip rocker.

The only way to have zero side thrust on the valve is with overhead cam actuation where the cam follower pushes straight down on the stem (there is still some wiping action of the cam lobe across the follower, but this is not translated to the follower/stem interface).

[geoffinbc]

Yes I follow you.

Again I would suggest a full roller rocker. It will reduce friction and give you that much more free power to go to the wheels. It also reduces oil temps and they are typically built very strong and will outlast a ball picot rocker.