What would be a good ball-park adjustment for a solid cam with unknown lift? I was thinking of going with LS6 specs just because I figured that would be pretty tame by today's standards. I have no idea what cam is in the car except that it is a solid in a 454. It idles very good and will idle as slow as 650 RPM but is pretty rough at that level.

Originally posted by 68454SS:
What would be a good ball-park adjustment for a solid cam with unknown lift? I was thinking of going with LS6 specs just because I figured that would be pretty tame by today's standards. I have no idea what cam is in the car except that it is a solid in a 454. It idles very good and will idle as slow as 650 RPM but is pretty rough at that level. Stock LS-6 specs will be fine. IMO

Rod

if you don't know the proper specs for the cam i would take a current measurement of all your valves so if it runs worse you can return to your current lash. mike

.022-.024 would be pretty safe

The lift doesn't matter. That is, even if you knew what the lift was, it still wouldn't tell you the lash it was designed for.

Most cams are set up for .020" - .024", WHEN HOT. Try values around in there first. Try setting it to .025", then tighten all 8 intakes some tiny amount (like 5° on the rocker nut), then try the same on the exhaust, and so on; try at least 5 or 6 iterations like that; and see if you can tell where the engine seems the happiest. Chances are, as you tighten them down, it will run a little better each time, until you suddenly reach a point at which it starts to run terrible; when you get there, you know you've gone too far, and what you need to do.

If you have iron heads and set it cold, set it to about .002" less than what you think it needs (like .018" - .020"); if you have aluminum heads, the lash "grows" by more like .005" since the casting will expand more than the push rods do, so set it to something like .015" - .018" cold.