g741.org

I have another problem I can't figure out.

Here goes:

I start the truck from dead winter cold.. Immediately runs perfect. No popping or missing. Partly choked. As it warms up the
Truck begins to stumble, or miss. Like a burnt valve or something.
Once warm the truck has the intermittent "puff" or "pop" like it's missing.

I checked the timing and set to TDC. Checked all plugs. Set to 0.025". No fouling or oil on any plugs.
A bit blackened and sooty like running rich.

Did a compression check. All between 105-95. Not greatest but its uniform

I am running a electronic ignition. No points.
When I did the conversion I did NOT replace the coil.perhsps this might be the culprit. However. Hear this:


Truck completely warm. Missing and popping and carrying on. Choke is now completely
Pushed in. It's now completly warmed up. No need for the choke.

So I try an experiment. I pull out the choke. As expected, it begins to stall on me.
Idle goes low. Wants to die. Just before she quits on me I push the
Choke back in. No more choke. As soon as I do the truck runs nice.!! But for a few seconds.
Still. It runs nice! No popping of missing! Wth! I keep thinking I
Got more carb issues then. Cant be engine internals like valves if it teturns to a great running engine for a few seconds!
anyone shed light on this?

Most common would be a vacuum leak. Put a vacuum gauge on it and see if it is steady and not low. Spray carb cleaner around base of carb and intake manifold gaskets and see if it doesn't pick up RPM. If it does, you have a leak.

I believe timing should be set at 4 degrees before TDC. Not sure if that will make a difference in your case? Also, maybe the choke is not closing all the way?

I also have a Pertronix ignition. If the truck is cold, it won't start without choking it, but as soon as it starts I need to push the choke in. I have my timing at 10 BTDC, and the truck runs great. I'm gonna advance it a little more even, but Im at 8000" elevation

update. First, thanks to all who read and answered.

I did try the carb spray trick.. Nothing changed..

I tightned all manifold nuts I could move, not that any of them were loose too much anyway.. still, the carb spray did nothing to alter RPM when sprayed.

I DID notice an exhause PIPE leak near the muffler.. so Ill have to address that now

but I cant see how a exhaust leak would do anything to the aforementioned issue... (or am I wrong here too?)

I didnt get a chance to re-adjust the timing to 4 degrees before TDC, or even 10, as you two replies suggested. I just plain ran out of time, daylight and needed to pack for home (and back to work today )

anyway, if anyone has any other suggestions I am all ears..