LOL.... I have been through this a hundred times. I have a 62, 235 and a Chevy tech told me long ago to adjust them
HOT .008 intake .010 exhaust
COLD .010 intake .012 exhaust
I adjusted cold and it worked for me. Your 58 probably has different specs though but certainly there HAS to be a cold setting because you have to at least get them in the ballpark to warm up the motor enough to do a hot final adjust. I found that adjusting them hot sucks big time so I always do it cold. I get them to where I can hear a slight ticky tick and I know that they are adjusted properly. People worry to much about these motors. Most of them will still be on the road long after we have worn out. Call the local Chevy dealer and talk to the service manager and see if he has a cold setting. Then if you must, you can fine tune it later.
