Carb Help needed!!!

[Wetter the Better]

ok here is the deal had it out 3 tymes and it burned down 2 of the three tymes.meaning a very lean condition and tulipped every valve in the heads both tymes,I had the distributor checked its fine.plenty of fuel pressure at idle and at the upper RPM's.The carb is a holley 750 vac secondaries 80508 on a 350 with sportsman2 heads,edelbrock performer intake.XM270 comp cam,10.53:1 compression flattop piston.The carb worked great last year but this year has been a no go.the only differance from last year and this year is the pistons and cam.Pulled the bowls off and look very clean but havent when any further in to it.the jetts are 77's and runs very rich at idle blackens the transom but it keeps burning up.I called AED and they also said a 750CFM carb but a double pumper.What do i do or where do i start?
picture is the first tyme it melted
can any of you please help out???
Thanks Stan

[victorfb]

does it idle fine? sounds like you may have a vacume leak somewhere. who is adjusting the valves? make sure they are closing all the way. they might be too tight, or just not seating properly. also check the main jets for obstructions. are your secondary's opening properly?

[Wetter the Better]

purrred like a kitten@700rpm.I have adjusted the valves as per comp cams instruction using the heel of the cam then adjusting till i get some resistance then go a 1/4 of a turn and lock the poly lock,main jets are fine have the carb apart now and there is absolutely no dirt,trash,or forein particles its spotless.and the secondaries are also working fine you can hear them come in and feel the pull and the gas i run is 92octane always
thanks stan

[Rexone]

A couple thoughts...
The carb you have jetted properly and working properly will not cause meltdown.
However idle mixture has little to do with top end mixture. You made a cam and piston change and now you have a problem you didn't previously have, I'm assuming with the same carb. You have 10.53:1 compression. What was it before?
Your compression ratio is marginal for pump gas. Also as you get close to the edge timing becomes critical. So my guess is you have one or more of the following 3 things happening contributing to detonation and the resultant meltdown ...
Not enough fuel (as in jetting or carb function)
Not enough octane (as in pump gas not being adequate)
Too much timing
I'm sure the engine and carb gurus can add more specific possibilities.

[Wetter the Better]

the compression was roughly 9.2 to1 stock dish pistons and a 64cc head and yes same carb as last year but these pistons are flattops.the timing is 10' intial and a confirmed 20' of advanced timing.i thought that 30' of timing i would be safe! and the plugs i use are AL#26. lack of octane will do the same?runn cam 2 aint a problem i just need to know,besides it smells awesome!!! i miss the smell from the race car
thanks stan