1964 C10 with 4.3 tbi father son project

I wanted to introduce our project and say THANK YOU to all of you who have taken the time to share your experience and knowledge for the benefit of many.

We recently completed a 4.3, 700r4 swap into my sons 64 pickup.
The drive train was from a donor 88, 1500 with a low mileage Jasper rebuild.
Utilized a Painless harness along with a salvage yard ECM.

I am happy to share that the truck is up and running well and being driven daily.>>> Happy 16 year old<<<

Everything is stock except the exhaust, no cat, single out the back.

I need to get a cable and attempt to learn TunerPro for datalogging so we can verify everything is good. I have read up on this and hope it is a not as difficult as I fear.

Have many questions to ask and am confident the answers are to be found here.

First one is with the timing; disconnected the timing wire and rotated dist. for 0. With the wire still disconnected the timing switches back and forth to a -6 deg. Its not a smooth transition more of a solid cycling back and forth about every few seconds.
With the timing wire reconnected the timing advances to roughly 14 deg. and continues this cycling of -6?

Any help would be greatly appreciated.

Again a big THANK YOU to all who contribute time, experience and knowledge for the benefit of others.

Todd

Can you raise the rpm of the engine to say 1000 rpms with the accelerator and see if timing becomes more solid? There could be some slack in the timing chain or wear on the distributor drive gear causing the timing to vary.

Hope this helps.
Brian

Check pickup coil and connection, correct module installed, and even proper timing light operation.