hesitation problems

[CenTxk5blazer]

Basics:
basically stock 350 engine w/ hei
eldelbrock intake
4160 holley carb

Fairly new parts (less than a year):
spark plugs
cap
rotor
spark plug wires
fuel filter

Yesterday, got a renew kit and rebuilt the carb. Today, everything hooked up and started it. When I get on it, it hesitates and eventually stalls unless I baby it. Went back and checked the accelarator pump, good stream. Checked for leaks and made sure everything was tight. Haven't checked the bowls yet to see if fluid level is correct.

The rpm is high at idle, the choke operates properly, I probably have the fast idle screw to far in.

Before rebuilding, it backfired through the exhaust. Now, I tightened the secondary screw further to allow more air.

Set timing using vacuum gauge, pulls about 18 Hg (think its the right units).

I did a search and tried to check everything that was mentioned as well as include anything that may have been previously asked. Any help for correcting this would be appreciated Thanks

 

[diesel4me]

Power valve??

The "power valve" on older holley carbs can get a blown diaphram when a backfire occurs,and it will dump raw fuel at idle and cause a bog or flat spot when accelerating if its not working because of the diaphram failure...did one come in the carb kit??--it looks similar to an oil pressure sending unit,screws onto the underside of the carb(have to take carb off to see it)...they fail often,and it does not take much to pop one..

It could be that...might be a bad pick up coil in the HEI too,it can cause backfiring and hesitation intermittantly...check good for any vacuum leaks by spraying carb cleaner around the carb base gaskets,andintake gaskets,any suspect hose or fitting ,that hooks to the intake,and listen to see if the engine changes speed,or listen thru a hose or stethascope while its running,any vacuum leaks will ause hesitation too..

 

[CenTxk5blazer]

The kit came with the power valve, and it was installed. I checked the pickup coil and replaced the coil on top the HEI when the cap and rotor was replaced. I've also sprayed it and checked the hoses. Doesn't seem to be any vac leaks.

 

[3 on the tree]

Is this a new problem, or did the carb do this before the rebuild? Check your fuel bowl levels. Does it spit or hiccup when you get on it? If so, it is prob running lean. Sounds to me like too much fuel, maybe float level is too high in the back bowl.