Cant get float adjusted
Thread Starter
Instructor
Joined: Jun 2008
Posts: 105
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Cant get float adjusted
I have a 750 holley vacuum secondary carb, ive been fighting with it to get the secondary bowl adjusted right. It is either the needle valve is adjusted all the way down so the float cant move at all or it just floods nowhere in between. This carb has a metering plate instead of a block and i found that if you tighten up the bowl the float hits the plate and wont rise and the carb just floods. I have the bolts as lose as i can get them with out fuel leaking out of the bowl and the float still hit the plate. Another question when i try to adjust the float and i unscrew the needle valve on the bowlm is fuel suppose to shot out of it when the car is running?
Burning Brakes
Joined: Nov 2000
Posts: 948
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From: Johnston Iowa
You could have a bad needle and seat. Take the needle and seat out and make sure that its clean. The smallest little particle will keep a needle from seating and cause a flood. If it looks clean and still does it the next thing I would try is to go buy a new needle and seat.
Advanced
Joined: Oct 2004
Posts: 62
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From: Bowling Green KY
Are you saying that the float is hitting the secondary metering plate? If it has the original nitrophyl (black) float, it shouldn't interfere at all. However, you cannot run a brass float on the secondary side if you have the metering plate, it will interfere.
As far as adjusting the float, keep in mind that it is a vacuum secondary carb, so it won't be using fuel out of the secondary bowl until the secondaries open where the front will be using fuel all of the time because of the idle circuits, and boosters until the secondaries open under load.
If the secondary level is too high, loosen the "jamb screw" with one hand, with the car running, just enought that with the other hand, you can turn the nut with a wrench. Turn the nut clockwise to lower the float level. Once you turn it 1-2 turns clockwise, look on the drivers side of the carb, see the secondary shaft? You will see a funny looking gold linkage that has a long slot with a rod going to it. With the car running, turn that linkage counter clockwise. It should open enought that the idle comes up and it starts to use the fuel out of the rear bowl. Your level should start dropping. If it won't open, crack the primary linkage slightly and then try to open the secondary with the other hand.
Hope this helps
As far as adjusting the float, keep in mind that it is a vacuum secondary carb, so it won't be using fuel out of the secondary bowl until the secondaries open where the front will be using fuel all of the time because of the idle circuits, and boosters until the secondaries open under load.
If the secondary level is too high, loosen the "jamb screw" with one hand, with the car running, just enought that with the other hand, you can turn the nut with a wrench. Turn the nut clockwise to lower the float level. Once you turn it 1-2 turns clockwise, look on the drivers side of the carb, see the secondary shaft? You will see a funny looking gold linkage that has a long slot with a rod going to it. With the car running, turn that linkage counter clockwise. It should open enought that the idle comes up and it starts to use the fuel out of the rear bowl. Your level should start dropping. If it won't open, crack the primary linkage slightly and then try to open the secondary with the other hand.
Hope this helps
Thread Starter
Instructor
Joined: Jun 2008
Posts: 105
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thank you 68 Blues, It had the brass float in it so i took it to the shop down the street and he put in a black one and set the floats for me.. We also found out that when i replaced the diaphragm i pinched it so i wasn’t work so the secondary wont even opening i guess thats why the car hant put out the kinda power i wanted. Think im going to notice a difference?
