The Stovebolt Site Forums The Shop Area Engine Shop Engine Sputter Under Load

1st swag is you've got a vacuum leak.
If you aren't running vacuum wipers make sure the vacuum tap on the intake manifold is capped off.
Make sure the vacuum line from the carb to the distributor is tight and not leaking. You can test it by disconnecting the line and plugging it at the carb. You'll get a hesitation but shouldn't stall.
Make sure the carb nuts and the intake/exhaust manifold clamps are tight.
You may need to use either carb cleaner or a hand held propane torch to further check for vacuum leaks around the carb base (throttle shaft) and where the manifold bolts to the head.

edit, does your carb have a manual or automatic choke?
Make sure it fully opens when you try to drive it off.
Another test to try is partially close the choke when you put it under load to see if it runs better. If it does you've isolated the trouble to the carb and narrows it down to either a vacuum leak or feul issue.


2nd swag is you're not getting enough fuel.
Disconnect the fuel line at the carb, while pointing the line into a container of some sort, have someone crank the engine. You should oberve pulses of fuel squirting in to the container, dribbles or very short/small pulses of fuel indicate eithr a bad pump, clogged fuel line, a clogged hidden fuel filter under the vehicle or debris cloggng up the tank.

I wouldn't tear into the carb until you've done all the easy checks.

Good luck
Dave