Inliners International Forums General Discussion Engines 250 valve adjustment

Gentlemen,
I have a 1974 Chevy 250, stock head, RV cam. when I adjust the valve lash I tighten the rocker. (stamped steel) until I can no longer spin the push rod with my fingers, then I tighten the nut an additional full turn , when I start the engine it runs crappy and the vacuum needle jumps around, when I readjust the most I can tighten the nut past zero lash is 1/4 turn or it runs crappy. any thoughts?
than you.
el viejo

One full turn past zero lash is way too tight. 1/4 turn is usually all that is required to achieve the optimum lifter preload of .025"-.045", which is what all hydraulic lifters made in the last 20 or so years require for proper preload.

Tightening until you cannot spin the pushrod is too tight.

You would make sure the lifter is not on the cam lobe (non lifting section) tighten the rocker arm nut until there is no up & down play on the pushrod, then proceed to tighten an additional 1/4-1/2 turn, usually 1/4 turn is good.

MBHD

CNC,
thanks for the reply. my Haynes manual days one full turn.
Have you ever run roller rockers ? Of so, is there any noticeable improvement in performance ?

When it is a stock cam, the factory adjustment is 1 full turn

MBHD