Hey I have a 1968 f250 that I swapped 90's f350 drive train in to it to make it a 4x4 highboy. I took a 89 300 efi and put 81 ford intake and exhaust on, as well a as 2100 autolight carburetor swap. Been a huge 2 year project. It starts and runs well just pings under load. Tried backing off timing/ running higher grade fuel but still the same. I have a 1970 distributor with pertronix in it. I'm thinking maybe the distributor needs to be recurved to back off max timing? I've been searching like crazy to solve this and nothing seems to fix my problem. Hopefully someone can help. I also think maybe fuel pump is not supplying enough fuel and running lean? Plugs do seem to look ok when I pull them. Everything is basically new parts. Any help would be great.

 

You can check the centrifugal advance with a dial back timing light. A 1970, 300 I6 is 1 degree @ 700 RPM and 22 degrees @ 4550 rpm at the crank.

 

Thanks for the reply. I will try that when I can track down a better timing light. However when I plug the vacuum advance it runs well and the pinging goes away. I only use this for around town and some towing. Will I see any negative affects by leaving the vacuum advanced plugged?

 

You have come close to diagnosing your problem if it runs with the vacuum advance disconnected. This distributor you have is it an original Ford distributor, or is it a new aftermarket? If it is an original then it should have a tag on it, post the number it should be something like C8TF-U for example. If it is an aftermarket, you likely have a made in China one size fits all and will have to plot the curve yourself using a dial back timing light and a handheld vacuum pump.
Most vacuum canisters are adjustable within their range of movement with an Allen wrench thru the nipple.
Do you have a dual or a single vacuum canister?

 

One other thing that is the elephant in the room is that you took an engine that was computer controlled and converted it to analog. You really need to find out by some means what the static and dynamic compression was on that 89 engine. When computers started controlling the fuel mixture and spark advance the factories were able to raise the static and dynamic compression way above what they were able to use with analog controls and not get detonation or pre-ignition.

 

Ok I also get a little pinging on my 81 F100 with the vacuum hooked up but been able to adjust a lot of it out with adjusting the vacuum advance can.
This only limits at what HG (vacuum) it starts to work at not total timing advance.
They say the vacuum advance can arms have numbers on them for the amount of timing it adds.

I started with a base timing if 16* BTDC started good with no kick back and little pinging even after changing springs in the dist. and adjusting the vacuum can.
It was worst when pulling a 20' enclosed trailer so I kicked the timing back, just turned to stop the pinging and save the motor.
I do not know what it is at but motor seams to run better when not pulling the trailer so I am leaving it.

I would say set base to 10* to 12* BTDC and see if you can adjust the vacuum can to being in timing later to stop the pinging.

I can also tell you running rich or lean made no difference on the pinging as I also run a AFR gauge.

I need to go back over my notes for the timing curve and see where I can adjust total with vacuum.
Or I may see if I can add more mechanical and leave the vacuum off?
They say between 30* to 34* total timing, no vacuum. I bet you are in the upper 40's to low 50's total with vacuum.

Oh question you running ported ore manifold vacuum to the dist.?
I run ported vacuum.
Dave ----