The original threads in the port were machine thread, unlike pipe thread which is a tapered thread. The A.I.R. port is in the exhaust passage downstream of the combustion chamber, even if the bolt/thread leaks a little, it is not leaking combustion or water or oil. If you get the engine running and there are no major exhaust leaks at the bolts, I would call it good.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
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