http://www.classiczcars.com/forums/showthread.php?t=6748&page=1&pp=15&highlight=valve+clearance

I just installed an N42 head with a mild cam (.441 lift and 260 degree duration). The person I bought it from said he had a machine shop go through it, resurfaced the rocker arms, etc. He ran it for 2k miles and decided he would go with one of his other heads. He warned me the valves were noisy, and they are.

They sound almost like a diesel truck idling. I've adjusted the valves hot and that's not going to resolve this. The thread above suggests that the lash pads are not the correct thickness for this new cam and the valves are not being closed properly. I will say it pulls really strong to 6k now, and overall I'm very happy with the performance. FWIW, I also noticed the exhaust sound at idle is now somewhat flat, compared to the nice deep sound with my stock cam.

I really don't want to tear it apart again, and I'm not sure I have the accurate tools to measure as required to get the size of the new lash pads. So my question is if I am going to do damage driving this as it is, and just ignore the noise?

I was told by two different engine builders that if I was going to use the same cam, rockers and lash pads to MAKE SURE I kept the lash pads in order and in the same direction (wear pattern) otherwise they would be noisy. I was told not to mix up the rockers also. I don't know if you will damage anything, but it stands to reason you will because the wear patterns are not the same.

He told me he had the rockers resurfaced, but I don't know if they kept the lash pads matched. But given the new cam has a different profile, I suspect the swept area on the rocker is not centered anymore, and this is what is causing the noise.

I probably have to deal with this eventually, but I'd rather do it when convenient as long as I don't cause other problems.

I suggest you sending phred a PM . He does this stuff for a living and is vary good at it.