So I've been fighting this one for awhile, I have a 1984 F150 4x4 which I recently rebuilt the 302 that was in it and added a mild torque cam with a 600cfm summit carb with a dual plane 4bbl intake. It performs well but I can't seem to get it to stop pinging. I have tried setting initial timing anywhere from 6* to 15* and it seems to ping bad either way. Seems to be loudest when warm and rpms are above 1700rpm. Also seems to be the worst in neutral,1st, and 2nd gear at a steady rpm. Does not really do it under alot of load. I have tried adding a richer and leaner fuel mixture and does not make a difference. Any help or insight would be well appreciated.

 

Are you saying that it pings while running with no load (in neutral)? That doesn't seem right. I would check to see if the valve lash are adjusted correctly.

I assume you've checked that the plugs have not built up carbon deposits.

Does the engine use EGR? If so, make sure that's working properly, as some of them do rely on the EGR to keep combustion temperatures down.

 

yea that doesnt seam right, i wonder if your dizzy isnt advancing properly. that would cause a ping in neutral.

 

There is no EGR system on it anymore. I just replaced the distributor due to a bad pick-up coil with a REMAN from the auto parts store. It did do the same pinging issue as it does now with the old distributor tho.

 

How did you richen the fuel mixture ? Via the mixture screws ? If you did that was likely your mistake. You'd need to rejet the carb to richen the mixture while it's running anywhere above idle. The mixture screws are idle mixture screws. I'd do as Kemicalburns suggested too and check to see if the advance is working. Granted the 84 head's huge combustion chambers don't help matters either but with the 8 to 1 comp ratio, it shouldn't ping.

 

I did rejet to richen the fuel mixture. It was blackening out the plugs tho so i switched back to the correct jets.

 

I have never ever heard of an engine that pings with no load, that would indicate another mechanical issue but for now you can install colder plugs in an effort to quiet the engine. Exactly what cam did you install and how did you install it.. retarded, straight up or advanced ?
Remove the distributor and ensure the mechanical advance and vacuum advance mechanisms are working correctly..
Use propane bottle with torch head and rubber hose to check for vacuum leaks around manifold and carburetor base plate.
Are you sure the carburetor is not clogged or malfunctioning and causing part throttle fuel starvation ?
Narrow it down until you find the problem..

 

I believe that cylinder 7 & 8 are crossfiring/missfiring and it may be causing the pinging?? There is vibration about 2500 rpm above 7 & 8 and it is only above them not the rest of the engine. Replaced the cap and rotor as well as spark plug wires. The wire for 8 is routed away from 7 so the only time they are close is at the cap to try and prevent it. Any thoughts???

 

Cross the wires at a 90 degree angle somewhere between the cap and the plugs, crossfire eliminated..

 

crossfire would cause a miss more than a pinging issue. i think your issue is with the distributor itself.