Bill:

I had a similar problem like that. When I figured it out it was the secondaries staying open slightly due to a sticking secondary throttle shaft. This happened after I washed the motor at a car wash. Where you driving in the rain?

Try some rust penetrate on the shaft and move to see if free.

marv

Well, in many years of automotive car repairs, restorations, drag racing and engine tuning, although forgotten most of the tricky tips, i,m wondering about this sympton thats just developed with my 750 D/P Holley on my 4/71 blower. Ted you may have struck this but i,m baffled at this stage prior to removing carb in next few days. With about 2000 miles now on engine, it slowly developed sticking throttle to where i had to blip pedal to return to low idle, its nothing thats connected to carb as it does it when disconnected. The strange thing is i have small additional return spring on carb so when repositioning it for more tension, i could feel pressure or resistance on the carb throttle shaft stopping it returning but soon as engine is turned off, the shaft just freely snaps shut without additional spring but soon as it restarts this resistance like a bent shaft feel appears. My thought was, would the air flow from blower put a force on the butterflys causing a pulling effect thus rotating the shaft? highly improbable but havent worked it out yet. i am going to check if butterflys are seated and tight?

  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia