Put together a 489 over the winter but hadn't had much time to play with it. I do have about an 2 hours time on it so I decided to re-adjust the lifters. It is a Comp Cams 294S and they recommend .22 both exhaust & intake. Prior I was at .28 for break in. But I just brought it back in to the .22. Lost about 150 rpm's and the idle roughened up. Didn't touch anything else. Looking for some input. :confused:

closing the lash will make the cam seem larger to the engine, since the valve with be opening sooner, and closing later.

Brian's right on the money...with .06 less lash, that cam just got considerably larger.
I'd re-check your vacuum reading at idle, and re-adjust the idle mixture on your carb as well.

Always, ALWAYS set your solid lifters on the tight side when breaking in a cam. Setting them too loose adds a lot of shock to the valvetrain and your new cam and lifters.

I have the same thing, my cam call for .026 hot and I have the lash set at .022 cold for breakin and deciede to keep it this tight after talking to Harold after the dyno. But if you want a better idle on the street and driviability I would suggest running the recommended valve lash , hot of course..

Originally posted by Zman:
Brian's right on the money...with .06 less lash, that cam just got considerably larger. .006 less lash, it only got slightly larger.

Try adjusting your idle mixture screws.