Motor almost dies when release throttle

[omegac1]

So my 440 six pack runs great but when I take foot off the gas and it returns to idle it almost dies. It does this driving and in the garage as well. It has power brakes, a big cam in it, and its a stick. If I blimp the gas a few times it returns to a good idle. I heard this is normal since it has low vac and that a vacuum tank would fix this?

 

[74 challenger]

had the same set up in my charger and never had that problem. Did you check all the vac lines? Spray carb cleaner around the carb base and see if the rpm changes. Gas filter clean? Just trying to help.

 

[Chryco Psycho]

I bet you have a 6.5 power valve in the center carb , you need to measure the vacuum at idle , in gear if auto & swap to a power valve rated lower then you minimum vacuum by about 1.5" . the easiest way into the center carb is from the back , remove the rear oarb & the center carb is easy to remove .
Also check your timing , you want about 16* at idle & 360 at 3000 rpm , you should dial out the vacuum advance so it doesn't over advance with RPM , there is an adjuster screw inside the vacuum advance on the dist , use a small allen key & turn it counter clock wise to limit the advance

 

[omegac1]

My distrib is a MSD unit without vac advance. I have the initial set to about 16. So the issue with the power valve is that it might be opening too early since the engine vacuum is low anyhow?

 

[Chryco Psycho]

exactly

 

[moparleo]

For safety , instead of spraying a flammable fluid on your engine, water works just the same. You are looking for rpm change. It could be lower or higher, same answer to vacuum leak, but safer.