I just bought this 86 Trans Am with a 305 TPI and 700r4. The problem is it spark knocks like crazy when under hard excelleration. I put 91 octane gas in it, new cap, rotor, plugs, K&N filter and pulled the catalytic convertor off and put a series 80 Flowmaster muffler on it. The car starts and idles fine. Please help.

 

what is the ignition timing at idle? at 5000rpm? has this motor ever been apart?
what is the compression ratio? what is the park plug heat range? Are you sure its a spark knock not broken pistons slapping around?

 

I'd start by checking your timing with a gun.

 

The motor is a GM crate motor with less than 50,000km, It was running good then it started pinging loud after I put a mechanical temp gage in it. The factory gage would not move so I replaced the sensor and still nothing.I left the sensor plugged in and tie wrapped it to the fuel lines and grounded it. Could it be the knock sensor or the spark control module ? I am new to any GM product, I was a mustang guy for 16 yrs.