2 replies to this topic

[m1n1]

Why is it that aftermarket cam manufacturers stipulate a rocker clearance of 15thou?

what is the benefit of 15 over 12 thou.. 15 gives a little less lift than 12 as the gap is bigger yes?

im using a sw5 on a 1380 with a big valve head. used to use a 276 but the sw5 is much more traffic friendly.

[bmcecosse]

3 thou less lift makes no difference - but that extra gap helps to ensure the valve always get's back to the seat - even when the engine is stinking hot and the exhaust valves have expanded with the heat. Ignore it at your peril - in fact - some would say use 18 thou on the exhausts.

[Pigeonto]

Why is it that aftermarket cam manufacturers stipulate a rocker clearance of 15thou?

what is the benefit of 15 over 12 thou.. 15 gives a little less lift than 12 as the gap is bigger yes?

im using a sw5 on a 1380 with a big valve head. used to use a 276 but the sw5 is much more traffic friendly.

If the manufacturer quotes a certain valve gap then the timing/duration of the valve opening and closing will be at the quoted gap.The change to the amount of lift is not really a consideration. Altering the gap can make a huge difference to the valve timing,may be better or worse,you can play. I was astonished how much sooner a valve will open just by reducing the gap a few thou.You need a dial guage on the valve and a timing disc on the crank/mark the flywheel through the starter hole to see the effects.

Edited by PIGEONTO, 03 October 2010 - 02:55 PM.