My 73 originally came with smog stuff. It was inexpertly removed and we're trying to deal with some of the resultant mess. The heads have been removed from the 302 and two of the 4 holes leading out (presumedly to the smog pump) have been closed off with thermactor plugs (that's what they look like anyway). I've been looking for some way to close up the remaining two holes but the thread size is killing me. I was hoping not to put an actual bolt in the hole but if that's what's needed so be it. Any thoughts on what thread size I'd need?
Should be able to use the factory threaded inserts available at a dealer. Ford part number F4ZZ-6E086-A
They are not pipe thread .They are 5/8 coarse thread ,a couple of 1in. bolts should do the trick. You may have to run a tap in first to clean the carbon out of the threads,
5/8"-12 thread. IIRC, I got bolts at ACE Hdw. I don't have a tap that size but mine went in the hot tanked heads OK.
if you take a cut off wheel and cut one or two slots across the first couple of threads on the bolts, it will work as a thread chaser and should clean any gunk out of the threads.
yeah I used a spark plug thread chaser to clean the threaded holes out, you can get one at autozone for about $7
