[vintagecar]

right around 1500 RPM when driving up to about 1800RPM the truck hesitates and pops. If I give it more gas it overcomes the hesitation and it is fine. If it is just cruising though or going up a hill and I enter that RPM range I get the same problems. If I'm sitting in park or neutral I can go through the powerband without any problems, it seems only under load does this happen.
350 V8, stock 882 heads, Crane Energizer Cam, 2000-2300 stall, headers, hei- initial timing is 16 around 600RPM and at 3000RPM its at 32. runs about 5 PSI fuel pressure. I've messed with fuel pressure as high as 9PSI and as low as 4.5 with no changes to the problem.

[slw210]

What does a vacuum gauge tell you?

[75gmck25]

You can usually resolve this kind of problem by going to a higher vacuum step-up spring on the carburetor. The standard spring on a 1406 transitions from cruise to power mode at 5" of vacuum, but the Edelbrock spring kit has springs for 6", 7" and 8" vacuum.

If you switch to an 8" spring it will make the carb transition from cruise to power earlier, which will richen the mixture earlier. This often cures the hesitation. Then try the lower values of spring (7, 6) until you get the lowest one that works.

You can also try increasing the accelerator pump travel by moving the rod to a different hole, but I'd try the spring swap first.

Bruce