Pulsating Throttle on 56 WCFB

[Mark P.]

Just started my 56 dual quad for the first time since a total engine and carb rebuild and the metering rods on the primary carburetor are pulsing up and down and the engine revs at 2 second intervals rather than iding smoothly. Is that a jet placement issue or a power valve spring issue? Any thoughts would be appreciated!

Thanks,
Mark

[Clem Z.]

Re: Pulsating Throttle on 56 WCFB

Just started my 56 dual quad for the first time since a total engine and carb rebuild and the metering rods on the primary carburetor are pulsing up and down and the engine revs at 2 second intervals rather than iding smoothly. Is that a jet placement issue or a power valve spring issue? Any thoughts would be appreciated!

Thanks,
Mark

try it without a power piston spring and see if that fixes the idle problem. if it does then find a spring that stops the pulsing by allowing the piston to stay down at idle

[Mark P.]

Re: Pulsating Throttle on 56 WCFB

Thanks for the response, Clem. So is the spring potentially too weak? Is that what's allowing it to drop?

[Clem Z.]

Re: Pulsating Throttle on 56 WCFB

Thanks for the response, Clem. So is the spring potentially too weak? Is that what's allowing it to drop?

at idle the vacuum should over come the spring tension and keep the power piston at the bottom of the chamber so the metering rods have the larger diameter in the jets,lean stop. you either have not enought vacuum at idle or too strong a spring. check your timing and valve lash as this effects the vacuum at idle