burned pistons

i have a blown 509 bbc that i runned for 3 years,with no problem . last winter i built a new car with some change on the engine , i bought dart 400 heads , indy intake and camshaft from oddy's , put a mds 12lt mag with crank trigger ,to replace my msd 10 set up, change my old square barrel valve for nitro style one . I stayed with the same tune upthat i had before. 14-71 front discharge, bird catcher , nozzle on port and hat , 11 to 1 ratio ,40/29 blower drive , 90 main jet , no hi speed . On the second full 1/4 pass i burned ( holed)pistons 5 and 6 and 7 suffered too all 5 other cyl pistons and plugs looks ok (cadmiun light grey) it look for me an ignition problem more than a fuel problem.
i need help

 

claude,when you changed heads&intake your 509 is now a different anamil.because the head&intake combination flows different than your old combo.now you need more fuel in cyl 5 6 7 .call oddy,he can tell you how much larger to go with those 3 port nozzels.also,with 11 to 1 compression i would start at 30degrees of ignition timing.

 

my previous engine was tuned with altronic 8 egt set-up and all the cyl temps was very close. i used the same jets at the same place .because i completed only the construction of the car just to make epping national . i made my first run there. I made one big mistake when i forget to install a tach converter msd 8132 on my altronic tach signal wire , then i did'nt have any egt reading. at this time . Mike i read one of your post under "timing " name , and i found very interesting when you talk about the crank trigger wire possibility of interference signal from spark plugs wire .
the timing is at 29-30 degres