'69 C10 327 SBC Off Idle Stumble / Misfire Help - I feel like I've tried EVERYTHING

[geezer#99]

Originally Posted by SRT8-X

Geezer#99, I'll give it a shot setting the timing at idle numbers lower per your suggestion. I appreciate you catching this!

I did not build the motor, it was purchased as a built long block which I went through and properly torqued all the main and rotating assembly connections. My father may have adjusted the valvetrain on the long block when we installed but I cannot recall. As far as I know, no valvetrain adjustments have been made. We were working on this project together for years and I can't be certain of everything he did prior to his passing 2 years ago.

Best to keep your idle down near 700 all the time. That way you keep the idle transfer slot covered correctly (your mix screws work then) and you’re not idling on the power circuit like you are at 900 or so rpm.
If it wants to die going into gear at 700 then you need more initial.
I mentioned lifter preload because it’s possible all your problems are related to a valve or two not seating fully.
Just another thing to look at.
If you rerun the valves just ask here for guidance here first.
And leave the carb alone until you’ve optimized your timing.
After all the motto is ‘Timing first, carb second’.

And your run on isn’t only timing related. It’s also caused by too much air which you’re feeding it with your primary throttle position.

And the other one is ‘99% of carb problems are actually timing problems’.