holley 4160 on 12a troubleshooting

[73Rx2]

hey there, ive got an 82 12a with a 600 cfm holley vacuum secondaries. the problem is somewhere in the carb, yes i know that its a little big but its the only carb i have. what happens is when the floats are adjusted before installation, ill step on the gas but no gas comes out. ill try starting it with the manuel choke pulled and it will come real close to runnin, but seems like it has a lack of gas, today i was able to rev it a couple times, but it only lasted a few seconds. when im not trying to start it no gas comes out ever, until i unscrew the floats little bits at a time then suddenly gas starts pouring out of both primaries and the secondaries so ill tighten the floats to where they were and it cuts off all the fuel again to where it wont even start.

If anyone could guide me in the right direction, it would be much appreciated, other than the float troubles, i also dont know where i should start with the idle mixture needles, or which one does what...

thanks,

mitch

[claudioz06]

sounds like one of your vacuums is bad that's why the fuel is not flowing consistently. The carb is big for the stock port 12A but not much, you can make it work by boring out the intake ports to let more air in. use .65 main gets and 31 jets on your barrel, power valve 6.5 and a spring kit for the vac secondaries..now once you get it started and the engine is running in idle, change to springs try them all one by one and check witch one works better

you'll probably need to buy the vacuums with the whole distributor which is about $260 (with both modules)

[clearkut]

Originally Posted by claudioz06

sounds like one of your vacuums is bad that's why the fuel is not flowing consistently.

you'll probably need to buy the vacuums with the whole distributor which is about $260 (with both modules)

are you talking of the 2 diaphrams on the distributor???? those have nothing at all to do with fuel, they control the vaccume advance of the distributor untill the mechanical advance system cvan take over, i belive at about 2000rpm, you can actually lock the distributor at full mechanical advence, or almost full advance and then the vacumes arent needed. i dont belive these would cause no start issues, maybe poor low end response from retarted timming but not a no start kinda problem,

hows your fuel pressure, have you checked? its very important in carb operation, the floats push against a needle valve to turn off the fuel flow at the apropriate level in the float bowl for the carb to work, too much fuel pressure and you may not be able to stop the flow of fuel into the carb. are your floats set to factory spec and not leaking if any moisture is inside the float replace it, it wont work if the tabs are bent incorrectly then it may not contact your needle valve when it is supposed to.


you need to get a holley manual, and a fuel pressuere guage, and start with the basics, my experience is with webers, they want about 4psi fuel pressure with the factory needle valves and will work with slightly more but not well, and most any good preformance aftermarket fuel pump can flood them out, i run a check ball inlet which lets me run a higher fuel pressure, but it is still important to set your fuel pressure to what your carb needs and start with the holley recomended float settings. from there i would find out what setting on the idle mixture screw is a recomended start point, (if they have an idle mixture screw) and once running another very benificial peice of equiptment is a wideband o^2 sensor

best of luck