I have two sets of exhaust manifolds. One has the heat riser valve removed and the hole welded shut, the other has the valve intact and working. For my summer only driven car, which one should I run? or does it matter? Both sets are 68/69 big block hipo manifolds.

I'm guessing it doesn't matter......Anyone with thoughts on this?

Unless the heat riser is working flawlessly (aspestos pad is there and spring is tight), I would remove it for a driver. I have one on my car for proper look and it works fine....however, sometimes when the motor is warm it clanks a few times...I'm considering swapping it out for a manifold with the hole welded shut.

Back in the day, that clanking was a pretty common sound with the hood up, I remember it. One of the first Day Two mods back then (warm weather states, at least) was to wire the thing open. For stock appearance the shaft & counterweight stuff needs to show, of course.

Thanks for the replys! I'll run without it, it's not a factory resto anyway and it doesn't sound like I really need it.

I'd run a carb spacer of whatever height your hood will allow and next time you change intakes I'd use a blocked valley pan. Todays gas is not made for carb'ed cars and it's vapor pressure resistance lets it boil at a MUCH lower temp than the 60's gas formulations in use when the heat risers were oe equipment