[Marshy]

Originally Posted by Lefkada

I will try cranking it over without the spark plugs today. I ran the motor last night with the valve covers off but didn't see anything obvious (the knocking was still there).

I had the original heads magnafluxed and they were found to have hairline cracks, so the machine shop give me a different set of heads and performed the valve job on those.

Do you know the casting numbers of your old heads and of the new heads? What pistons are you using, flat/dished/dome? Do you know how much deck clearance you had..? Are you running an aggressive cam?