I hear you on the poor gas quality... That is why my new 440 Mr Six Pack Attack build is going togehter at 9.5 to 1 compression using 906 heads.

Do you have the manifold exhaust heat crossover blocked? Also are you running a 160 thermostat? Cool is always better to fight knock...

Can you at least get Non-ethanol 91 octane? I believe it will work better. here in Canada, the SHELL 91 has no ethanol, but other 91's do!

Good luck with it.

Arnie

67 Cuda 8.48@ 158.7 mph 1.18 60' 2,600 DA(so far...) 70 Super Bee 440 Six Pack 4-speed. 13.2 @ 104 Stock exhaust/Street tires.