Carb stumble in hot traffic

[ROWSC]

I drove my short-stroke 3.2 to a faculty retreat yesterday. Going out of town in late morning was a blast, but returning in the rush hour heat was problematic. I have PMOs sitting on stock manifolds (that have been machined to match the larger ports on my 79 heads). I also have the heat absorbing spacers between manifolds and heads. Under normal acceleration, the engine would falter between 2500-3000. Disengaging the clutch, blipping the throttle sharply, and reengaging the clutch at 3500+ solved the problem until the next time I came to a stop. Continuing to push the accelerator to get above 3500 did nothing to smooth out the engine.

I have a Innovate LM-2 wideband O2 reader, but I have held off on any type of carb adjustments because my plan is to install the tall PMO manifolds and don't want to mess with the carbs more than I have to. Any "simple" fixes until I get the new manifolds?

Rich

[Steve]

Rich,

Don't delay adjusting the carbs as needed!!!

I would check float levels VERY carefully as they must be perfect. After that, check & adjust accelerator pumps as needed, if your idle CO is OK, to prevent stumbles as you accelerate.

Start logging some AFR's numbers at idle, part-throttle & full throttle.

Tall manifolds will not appreciably change things below 3K RPM.