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Old 02-27-2012, 08:26 AM
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Originally Posted by Russchiappa
Hello, I am new to the forum. I like alot what i have read so far, so maybe someone could help.
Ive posted this elsewhere but have no success.
Chrysler 1958 392, fresh rebuild, with now 1500 miles on it.
10 to 1, msd electronic dist., mild cam, balanced /blueprinted, running a 750 edelbrock, with headers.Motor really purrs.
This is the problem: car starts, runs and idles well, but when i step into it, and rpm rises to about 3200rpm, i get "pinging", or the motor runs rough. Wont pull any more beyond this. If i accelerate slowly, the car will drive 75 , 85 mph.etc.
I believe i have the timing set to 12 degrees initial, 30 degrees total, all in by 2500rpm. I have switched the advance springs in the dist, run without vacuum advance, to no avail.
I am getting adequate fuel, and switched carbs from holley 750 to the edelbrock thinking the trouble was fuel related, but i am pretty certain it is ignition now. btw, matching msd coil, 8.8 mm wires (msd also )
something is amiss. Thinking of send dist. back to company for checkup.
Thanks for any thoughts.
392 Hemi combustion chambers/pistons aren't known for their "quench", at least not in the same sense as a wedge chamber w/quench pad(s). The domes needed in most higher compression applications also don't do a lot for flame propagation unless some tricks are used, like Dick Landy did on the Hemi piston on the right (below):

Because of that- and just because that's a lot of CR for ANY engine w/iron heads and a mild cam- I would be looking at the dynamic compression ratio- using 10:1 on an iron head Hemi w/a "mild" cam and today's for-**** gasoline is an invitation to severe detonation.
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