I have a 76 460 holley 3310 carb, my question, it purs like a kitten when at idle, rev it up a couple times then it starts poping out the top of the carb. I just went through the carb, jets 70 power valve 6.5, the only thing I did besides clean the carb was replace the PV, it didnt do this before.
Thanks for the help?

 

R-3310-780cfm? Fuel level set properly? Hopefully you haven't overtorqued the bowl screws. This will warp the main body and create a leak at the pv supply port. Needle and seats been replaced? It sounds like a fuel supply problem, or seriously fouled plugs. This is not a common complaint with the 3310. Go over evrything you did and you will find the problem.

Hope this helps a little
Roy

 

thanks for the reply Roy, I have gone over everything 10 times, everything seems to be set right, now if I did get the bowl bolts to tight is this a permant problem I have caused or will letting a little torque off help?

 

If you look at the throttle body casting where the 4 bowl bolts go you will see that it is quite thin. Place a straight edge on the flange and see if it bows in the center. If so you can place the bowl screws in the hole and lightly tap them to get the casting flat again. You must take it easy since this is a casting and may want to break. I used to flat file them perfectly flat but this takes time and all the passages then need to be de burred and champfered properly. Once the bowl screws are overtightened letting the torque off does'nt fix it. You probably didn't overtighten them that much, I hope.

Check the accelerator pump jetsfor a good stream and after it starts to backfire check to see if there is still fuel squirting out of the accelertor nozzles. If not then you might have a problem with the pump diaphragm or fill port

My friend just put in a new engine and when it wouldn't start he used a 2cycle gas/oil mix to prime it. He had popping through the carb similar to yours. The fuel/oil fouled his plugs. Did you pour anything down the carb? I am trying to help and racking my old tired brain for anything that could cause this. When you pull the bowl sight plugs at idle you should have a trickle of fuel running out. Please be careful with the float level adjusting lock nut. I have seen these stripped out many times. Any more info you could give would help us figure this out. Make sure metering block gaskets are correct and no passages are blocked.

Roy

 

It could be timing if its backfiring through the carb, it could be an intake valve sticking at higher RPMs too....

Ive seen weirder coincidences than doing a tuneup item and having something totally unrelated go wrong