Here's my two cents worth.
I started playing with engines in the late 60's, had my Lola T-70 running since 1978 with a roller cam in it.
I've allways set lash cold and had NO valve related problems.
I now have aluminum heads on the engine and set the lash .002" tighter than spec when cold. With iron heads just set at the recomended spec.
Stuff I've read over the years says the block, heads, pushrods etc all heat up the same rate if made of iron and steel.
The aluminum heads expand a little more than the steel pushrods so you need to close it up a little.
Those who lash the cam hot. The engine get's much hotter than that when racing or driving down the road at higher rpm's.
So "hot" is a somewhat relative term.
I just have found that I can pull the valve covers, lash the valves accurately and calmly without rushing, replace the valve covers carefully, get everything properly in place and ready to go out on the track with the engine cold. If I get the valve covers on wrong and get a leak, I'll get black flagged and miss my practice group, so doing it with the engine cold is better for me.
By the way, I'm using an Isky roller cam and it's 640 lift, so if I were very far off in adjusting it, I would be having SOME kind of problems by now!
My engine builder does valve adjustments this way too and has done CanAm, and Southwest Tour engines for years, in addition to drag boat engines.
The 30-30 cam has a LOT of lash, .030" is a lot of lash and I've read where you can close it up 2 or 3 thou when experimenting.
I wonder if the high amount of lash is really there to allow for the guy who just drives the car and never re adjusts the lash. In other words, as a safety margin because this cam is a production vehicle cam. If that's true, there would be a very large range of leeway in lashing the Z/28 cam.
Many aftermarket cams use .008" to .012" clearance.
I'm not trying to put down anyone who likes to hot lash valves, I suppose it's pretty accurate. I just don't like working on hot engines.
Check my web page for First Gen Camaro suspension info:
David's Motorsports page
First Gen Suspension Page
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350
Can Am Vintage Racer
[This message has been edited by davidpozzi (edited 04-27-2001).]