1955 ford 272

[whatdoyouwant]

My 272 coughs and sputters while accelerating in first and second. It runs fine in third and overdrive because of lower RPM. I checked the vacuum at idle and it is between 15 and 16 and the needle shakes. This is at 500 RPM. By turning the carb air screws, I can lower the vacuum but never raise it any. I have taken the hose that runs from the dual acting fuel pump to inside the car and plugged it with no change. So I don't think I have a leak it the vacuum hoses. This has done this for years and I changed to electronic ignition with no change.
any thoughts would be welcome.

 

[Gene F]

Is the carb loose?

 

[KULTULZ]

GO HERE - https://www.onallcylinders.com/2016/03/31/vac-visual-quick-guide-vacuum-gauge-readings/

 

[whatdoyouwant]

Thanks KULTULZ, the readings should be real helpful. Another link on that page said these readings are at sea level, and for each 1000 feet above the reading will drop one inch. I am at 6000 feet, but still wonder if I have late timing. Have you experienced this with late timing?

 

[KULTULZ]

In regards to IGN TIMING, you have a LOAD-O-MATIC SYSTEM and proper initial timing and advance needs to be determined (and corrected).

- https://www.classiccarrestorationclub.com/video/engine-vacuum-troubleshooting/

- https://www.motor.com/magazinepdfs/082001_05.pdf

The VACUUM GAUGE should point you in the direction of the problem(s).