Testing the HiRev 7500

92b said
I'm not saying that boxes don't retard but I have seen timing retard go from 6ish degrees of retard to 1ish degree with the same box and two different types of distributors. On running engines not a distributor machine. I don't know for sure but I think the results will be the same on a distributor machine. Most test including this one are done with the same type of distributor. Self generating ac signal.

I absolutely agree 100% that with some cases, there's more than the box in play. No doubt about it. But the only way to know it to TEST!

65 Cuda 340 said
Okay, for us dummies who are struggling to understand this, tell me if this is correct. The timing retard on all these boxes doesn't really become significant until high rpms. 7,000, 7,500, etc. For a motor that only goes to 5500-6,000, it is not a significant problem.

Right? Or have I completely lost my way?

It depends on the type box and how crappy it is. Some actually have high RPM retard designed it to help protect against detonation at high RPM.