Question about valve lash

[blykins]

It's because all solid lifter cam lobes have lash ramps built into them. This is a slow acceleration portion of the lobe, meant to slowly ease into things.

You can close up the lash a little amount (as I did initially, as your cam card actually says .028"/.030"), as that does change the cam's personality, like John stated above. However, you can't get too carried away with it as you can change the dynamic (read 'violence') that your cam lobe and lifters usually see. Solid cams are different than hydraulics by the fact that you spend a little amount of duration taking up that lash before parts actually make contact and you start opening valves. When you tighten up the lash, you essentially make the cam think it's bigger than what it is. Conversely, if you loosen lash, the "effective duration" of the cam is decreased.

Lash depends on the cam lobe's individual design, and it's calculated by multiplying the lash ramp that's built into the lobe, by your rocker arm ratio. You have a Bullet camshaft, and some of their lobes use a good amount of lash. Others, like some Comp Cams lobes that I have here, work on .016/.018" hot lash. It's just a function of the design that the particular lobe has in it.

The cam designer puts a spec on the card where he wants you to be, and you can vary a few thou in either direction, but that spec is put on there for a guideline.