My friends cyl head shop would completely fill & recon tour SBC heads for super stock class. Ports had to be the same volume as stock, they looked nothing like a SBC port after he was finished with them. He did use some sort of higher priced two part epoxy,(one gallon sized can) but IIRC, he said JB weld worked just as good.
NOT the JB QUICK I do not believe they never had a problem with the epoxy coming loose & damaged the engine, but they also would freshen up the heads & epoxy every so often, this was a race car, not an everyday driver.
I used JB weld on the intake ports of my two stroke ( has gas & oil to deal with) road racing bike, it would eventually chip off little pieces here & there, but I was making the ports a different shape & was not sandwiched in between a piece of metal like a lump port would have.
I would think if the gaps are not horrendous & do not redirect airflow, filling the gaps would be of no benefit other than cosmetic. IMO.
Being the gaps are just on the back side of the bolt in lumps, I doubt it would make any difference if you filled in the gaps.
MBHD
