Well the subject says it all I suppose.... should I use epoxy to close/seal the gaps left over after fitting bolt in lumps in the 230 intake? The gaps are pretty noticeable deeper in the port, while I have pretty much zero gaps facing out. I could apply some epoxy filler in there and then bolt the lumps in place, and let the excess squeeze out and trim it before it hardens, should require minimal cleaning after its hardened. What would be the best stuff to use, that won't break down and require re-doing, like EVER?

I don't recommend for street use. Too much chance for it to work loose later.

That's my thinking too, I have had it in a race engine and it held surprisingly well, never saw it come loose. But I never trusted it. I would rather not lose my sleep over it every night.

if you use the right epoxy(high heat)and rough up the surface it adheres to with 40 grit paper to give it some thing to stick to, it should be ok. especially if its trapped between two surfaces like gap. plus its pretty soft stuff if it has no filler like aluminum or iron, chances are if it came loose it would blow thru and out your exhaust pretty quick without any damage. back in the day Petty enterprises did port reshaping with epoxy.

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