I have a couple of question pertaining to stock, cast iron exhaust manifolds.
First, what's the purpose of the tiny spring on the rear side of the heat riser valve? I'm not talking about the one behind the counter-weight that closes the flapper valve, I mean the one on the opposite side that rides on the flapper valve shaft and the small pin that runs parallel to the shaft. I've seen one on every slant six exhaust manifold I've had my hands on, it just seems that this little spring doesn't really do anything, it's just along for the ride.
Second question, exhaust manifold outlet flange to exhaust head pipe mounting studs, I'm familiar with the 7/16" studs that screw in to accept a gasket, the head pipe flange and nut. Is there another fastening option for this connection? I have one exhaust manifold with smooth, drilled holes that are larger; a 7/16" thread tap slides right in. I wasn't sure it there was a through-bolt mount on some applications, or if maybe this one may have been drilled out sometime during its existence.
Thanks for sharing your thoughts and experiences.

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1975 Dodge D100 225 c.i., HEI, Offenhauser Four Barrel Intake, Parallel-mounted 500 CFM Edelbrock, Split Cast Iron Exhaust, 904 auto, 9.25" 3.55:1

either way works, thru bolt or stud and nut. I wouldn't lose any sleep over it. The thru bolt/nut is more forgiving, if it breaks off when taking apart, "so what". if the stud snaps (or strips) it would be more of a pain to fix, especially from under the car.

Thanks Don. That's what I was thinking too, just never seen another one like that and am curious about it's origin.
Have you got any ideas about that little spring?

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1975 Dodge D100 225 c.i., HEI, Offenhauser Four Barrel Intake, Parallel-mounted 500 CFM Edelbrock, Split Cast Iron Exhaust, 904 auto, 9.25" 3.55:1

It's there to prevent the shaft from rattling/ticking once there is no tension from the clockspring to dampen it.

Anti-rattle.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

And now I know.
Thanks, everybody for your responses!

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1975 Dodge D100 225 c.i., HEI, Offenhauser Four Barrel Intake, Parallel-mounted 500 CFM Edelbrock, Split Cast Iron Exhaust, 904 auto, 9.25" 3.55:1