I have a 96 5.9 magnum with this cam
Voodoo Hydraulic Roller Cam - Chrysler 273-360 (W/ Long Snout) 258/264 - Lunati Power (the roller version of a similar cam) and am having the same problem with detonation. Seems to be a problem with that grind (or a mix of higher compression and lower duration) and some more overlap would definitely help bleed off some of that cylinder pressure. Had to mix half a can of race gas mix with a tank of 91 octane gas which seems to have stopped it but I sure hope I don't bust a piston like happened to you.
The maximum Scr to run with this cam is about 9.4, to get a Dcr of 8.0@160psi. This should run on 91 no problem with iron closed-chamber heads. If it doesn't;you may be feeding it timing too fast,or too much,or possibly the carb is off, or it is just too heavily loaded, or running too hot.
It's not the lack of overlap that "bleeds off compression but rather the intake closing angle. Yours might be close to 55*ABDC. A bigger cam might close at 65 or even 75. These bigger cams allow the piston,at low rpm, to push some intake charge back up into the intake, thus giving up some Dcr (EDIT: correction EFFECTIVE compression). Once the engine gets wound up a little, usually a bit over 2000 rpm, there is no longer time for the air-charge to turn around and go back. At this point, the Scr becomes the limiting factor as to freedom from detonation.So from here to about 3400 rpm,(EDIT; or perhaps up to 3600) the ignition timing may be critical.
As the engine reaches peak torque,it will be pulling in a maximum amount of air per cycle. Then as the engine continues up the rpm scale, the available time to pull in air is continually shrinking.This is when the extra duration of a big cam starts to pay off.It stretches the available "time", by stealing it from the ends of the cycle.
You may know all this,IDK, but I think it's important to mention where the "bled" cylinder pressure goes.
During overlap, when both valves are open,the headers are tugging on the plenum, trying to get the AF charge moving early. The piston is stopped or very nearly stopped at the top of the cylinder. Then when the piston moves down and the exhaust finally closes, the charge is already moving into the chamber. There is no compression being "bled off" here.
EDIT; added
With manifolds there is no tugging, and that is why we don't use them in hi-output engines.Where is the switch? Well the factory boys thought manifolds were good enough for 340s. They were probably right; the 268/276/114 cam only had 44* of overlap, so not a lot of tug happening there. But if you tighten that same cam up to 108, then the overlap is up to 56*, and this should show a good improvement, with headers starting to tug pretty good. The 292/108 cam has 76* of overlap, and properly set up,the headers are now seriously tugging.In fact, by now, the overlap period can become more powerful than the actual intake cycle. And that is why high overlap cams use so much fuel at low rpm, the headers are tugging the AF charge right across the top of the piston and out the port and down the pipe to the atmosphere, unburned. But they sure sound good doing it!
Hope that helps.
