carb problem

what could be causing my secondarys not to open up on my 600 holley it is a vacum secondary carb.it is fine at low rpm but when i try to get into it its not working right seems like the butterflies are not opening up and it stumbles real bad until i let off the pedal then it picks right back up or if i ease into it its ok.
thanks
john

 

Did you match your power value to the vacuum your engine is pulling?

 

i believe the power valve has a block plate in it im trying to get ahold of the guy that rebuilt it to find out i was there when he did it but i cant remember the situation and i had a new powervalve there but we didnt use it.

 

You absolutely need to use a power valve, and most kits come with a 6.5 valve, which may or may not work with your engine. You need to get a vacuum reading to get the right PV for your application.

 

By all means, check the PV first. Without the PV, you need to jet up around 8 numbers which kills the idle and gas mileage. As for your problem, it sounds like the butterflies might be opening too quickly causing a lean bog. Any way to get someone with a wideband O2 rig to check you out?

 

Sounds to me like the secondaries are opening, but there's no fuel coming out of the booster venturis. What spring is in the vacuum pod ? Check the float level in the secondary side. The powervalve in the primary's going to be a 6.5. The secondary won't have one. It will likely have a metering plate instead of a metering block there. Even so there's no p/v used on the secondary side.

 

problem solved, my welder came over to help on the mav today and we figured out that the set screw on the arm for the secondarys was missing so it was a linkage issue will fix this weekend but we did put a wire on it and when them secondaries kick in wow that carb lights up.so thanks for all the input guys.
john