ProComp/Speedmaster aluminum heads

Well, I'm obviously not in support of a loose chain. Neither am I opposed to gear drives. lol. But, a decent chain will survive for years - and proven consistency are in those that bracket race every weekend and the ET doesn't change. Many bracket racers I know run chains, some don't tear their engines down in 3-6 years, and they can dial and run to the hundredth, maybe even thousands of dial in time. Also, the car over the course of that time usually won't slow up - if anything, it will run a couple tenths faster after a 100 runs. Oh, the only way your method of "bouncing 20* under load" works to show chain flop is if the distributor is locked. I'm not trying to educate the educated, but as you say, somebody else might be reading through this thread and I'm just trying to get a perspective out there..... :)

No, they flop with an advance curve in the distributor too.

So if the chain gets loose and the car goes faster, that tells me the the ICL wasn’t correct for the application. If it’s correct and the cam timing retards they will lose power and slow down.

You also need to run more P/V to make up for the exhaust valve clearance getting eaten up by cam retard.

FWIW most any decent bracket car is running a timing belt any more. Just the stubborn cheap skates run chains. That’s just the truth of it.