Trying to bleed off a little compression. Current cranking compression is 200 using iron heads and a cam with 241 duration at .050. I would like to be at 180-185 Im concerned with loosing bottom end power. Can I go to 250 - 255? I read Andys articles and they have helped me in the past

If it is a solid lifter cam, tighten the lash. Back the cam up to "straight up" (ICL=LSA) or 2° retarded. Depending on where you are at with these now, this might get you close.

What cam is it? MP .528? What is the advertised duration, and LSA?

What size engine?

I'm assuming you are wanting to lower your octane requirement? A longer duration cam would lower your cranking compression number but would reduce driveability as you would lose bottom end power but first (it'd be easier/cheaper) I'd get a multiple keyway timing chain set & retard it 4 deg & see what develops. As you know recheck valve to piston clearance when advancing/retarding as either the intakes or the exhausts gets closer & the other gets farther away. Not sure which would be more effective on what you are after either a longer duration cam or retarding your current cam cuz I ain't a cam guy but just me I'd retard your current one first. Holler how it turns out

Conventional thinking on exhaust manifolds or any inefficiency in the exhaust system is to open the exhaust valve earlier so that the supersonic "blowdown" lasts a bit longer on the exhaust stroke.

It never made sense to me to open the exhaust valve early because it seemed this wasted the still expanding gases pushing down on the piston during the power stroke.

I finally understood it when it was explained that if you dont open the exhaust valve when there is still quite a bit of pressure, you dont get a short period when the gases accelerate past the speed of sound and create a sonic boom like a jet fighter. This sonic boom has a high pressure wave at its front, but also a strong suction wave just after. The cam designer wants this suction wave to pull up the piston on the exhaust stroke, which reduces the power the other cylinders would have to apply to raise the piston.

Does residual gas in the combustion chamber increase the chance that detonation will occur with a high compression ratio?

Mazda seems to think so
on their new 13 to 1 compression ratio
Skyactiv line of engines.

In their press release they spend time explaining that their Tri-Y exhaust manifold was necessary to get the compression ratio high without detonation on 87 AKI gas. At full throttle they claim that the heat brought in with the residual exhaust gas is a bad actor that had to be reduced.

If your 200 psi cranking pressure is causing detonation,
in addition to cam changes
consider grinding a few more CC's of combustion chamber volume on the exhaust valve side

Yes, it is the .528 I will try and tighten the lash and see what happens. straight up is actually 2 deg retarded? thanks

one of the problems with the 284-.528 is mopar performance's .028-.032 valve lash recommendations.. using .022 or .024 as a starting point will get the seat timing a lot closer to a real 284 degrees. this is probably a case of too high of a compression ratio for pump gas. also factor in the heat that cast manifolds run at, 700+F, and things can stack up. an asymetrical lobe camshaft is a benefit in reducing cylinder pressure. even if the pressure is reduced to 180psi there's no guarantee of smooth sailing. the tune up will be critical.

I would also try to tighten the lash, I run 205 psi on a j head 360 run about 30 total and I run a very cold plug seems to run fine for the last 6 years or about 7k miles. I love the pop of the hi compression!

I am also running 200 PSI cranking.. typically 93 octane Shell and I am good to go.. Stock Iron manifolds.
I realize that 93 octane is not available everywhere.
there are other ways to knock down octane requirements, including, lower temp thermostat, fuel mixture, and spark timing events, gearing etc....to try, before you tear into the engine..

why?