BK N 66

i have a 350 4 bolt main bored .30 over. i have aluminum trick flow
64cc heads 195 cc runners. i am running a comp cam thumper cam
with lots of duration and overlap. it pings like hell and diesels when i
shut it down. i even went to mechanical advance on my msd ignition?

i even went to down to 8 initial advance down from 11??? it still
pings??? what can i do? should i try thicker copper head gaskets???

thanks for your help..

Matt Gruber

What rpm does it ping?
What advance does it have at that rpm?
Is it too lean? No?
Then reduce timing curve. Post advance every 500 rpm.
Read my articles(in sig) click thru to 1 with pv suffix.
Extra credit: Add cold air intake(worth 5 octane)

Avispa

Thicker gaskets may not be a good solution. They'll drop the compression but then you'll have too much thickness in the quench area of the head. That needs to be on the order of .040 to .045 inches. It is possible to make the detonation worse with thicker gaskets, depending on the combustion chamber and piston dome shapes.

JohnZ

I'd bet that cam is driving up your dynamic compression due to higher cylinder pressure; the factory cams in the 11:1 engines all have late-closing intake valves to bleed off cylinder pressure, and aftermarket cams don't.

If it diesels when you shut it down, the throttle plate is too far open, and it's probably idling on the transfer slot.

What do you mean by "went to mechanical advance"? Does your distributor have both centrifugal and vacuum advance?

Jims66

I have a 0.30 over 327, 64cc iron heads, L79 (151) cam, Holley 750 cfm (72 Primary jets) vacume secondary carb (#3310) on stock 350HP alum intake. The compression was measured at 11.1:1 and I run on 92/93 octane pump fuel with no ping.