Hi
I have a 79 K5 that I had to put a brand new 350 in a few months ago. The timing has never been right since. Every time I turn it off it rumbles and shakes loudly for about a minute and then shuts off. Yesterday, using a timing light (for the first time) I set the initial timing to 12 at idle and went for a drive. It felt really good but I couldn’t get it above 40mph, it felt like all the power was lost. I then tried to reset it back toward what it had been set at (much higher than 12) and it ran roughly and shut off on me while driving then backfired loudly when I ultimately came to a stop. Please help!

 

Are you disconnecting the vacuum advance before setting the initial timing? Also, if you rev the engine to 2500RPM or so, does the timing advance?

The dieseling (run-on) has nothing to do with the timing. Think about it for a second. When you turn the ignition off, there is NO spark. So it doesn't matter if the non-existent spark is advanced or retarded. It's generally caused by hot carbon deposits in the cylinders, combined with a too-high idle speed.There might be a vacuum-operated (or possibly electric solenoid) idle kicker on your carburetor. If it's adjusted properly, it should help.

 

Would also need to know the setup.

OEM carb and ignition?

Aftermarket carb and ignition?