I am gong crazy trying to figure this out. I have a popping/knocking sounds coming from my throttle body when the engine is under load. Only under load, if i bring the rpms up slow, i get now popping. If i rap the gas, the noise is there.

Here is what i have done so far.

New plugs, wires, iac motor, check fuel pressure, re-did all vacuum, re-checked timing(car seems to idle/run best at 0 degress,L98)


The motor is a 355 with a mild cam, headers and head work. I have a chip tuned for injector constant.

I need help, i am not sure what else to check.

 

double check you plug connections and firing order on the cap
1 8 4 3 5 6 7 2

and maybe check your timing too (disconnect the brown/black wire)

 

Only when it's under a load? Could be detonation. Pull a plug or two and see what they look like. If the ceramic is chipped/pitted then you definitely have a detonation problem.

Does your chip still have the stock fuel and timing tables or have they been modified as well? Head work will make a huge difference in the airflow characteristics of an engine.

Also, base timing for a TPI car should be 6 degress, unless it's programmed otherwise in the chip.


edit: Don you have your 6 and your 5 backwards. It's 1-8-4-3-6-5-7-2 for a SBC.

 

does the motor seem to idle in gear as it did before the noise started? no misfire? does it run any different now than before?

if you can find no other problems, a sharp rhythmic pop under a load that increases speed with engine speed & intensity with throttle opening coming from the TB could be caused by an exhaust valve not opening because of a problem with, 1, a rocker arm, 2, a push rod, 3, a lifter, 4, a flat cam lobe.
not near as sharp sounding as an exhaust valve not opening is an intake valve not closing. which could be caused by 1, a rocker arm, 2, valve spring, 3 a stuck valve, 4, a lifter.
you would need to pull the valve covers & check each rocker arm, push rod, & valve spring, for a valve not opening you would need to watch the rocker arms with the motor running.

 

I have seen the valvetrain move freely when running. Everything seems ok there.

 

ttt