Having trouble diagnosing hesitation/stumbling

Killer6 said

One issue that crops up on smallblocks is the heat crossover plugging up w/carbon, the ports in the heads and the intake will completely be closed off. This will cause hesitation
and a choke/fast idle that takes too long to open/idle down, just an addtn'l thought. A bone stk. eng. shouldn't run poorly w/the stk. vac adv hooked up, but too cool an intake
will run lean, and the advance may cause a surge when it's pulled in as a result. I would change that t-chain jumped or not at that age & mileage anyway, good luck!

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My 71 Windsor 318 w Rochester 2 bbl, when my parents bought it for 450 in Oct 1980, was dead-dead.
Put a 66 Carter 273 carb on it, fix a flatted two tires after busting off two normal thread studs, and drove it home less than a mile away. Pissed off the PO to see me drive it off. But the choke was very sluggish..
Always too much or not enough, hot vs cold.
And I'm the mechanical spring coil carb linkage bending whisperer who can make it perfect, and it ain't working.

F!

Pull the manifold.
Crossover plugged with rock hard carbon deposits.
Thanks, Rochester.
Many hours with chisels, screwdrivers, welding rods, and it was open.
Choke, pull-off, everything then could be adjusted to work like a perfect new car.
This is a situation that feeds on itself and makes itself worse in time.