RJS
Jedi Warrior
Offline
Hi
I need some help. I spent all day yesterday trying to get my rebuilt carbs dialed-in (SU HS6s). What should have been a 2 hour job became a very frustrating all-day affair.
My issue is a hanging throttle. I got the carbs balanced, mixture set and idle at 750 RPM. But, if I slowly take the RPMs up and let off the gas (i.e. crusing and coming to a stop sign) it will hang at 1,500 to 2,000 RPM. If you snap the throttle, it will drop back to a nice 750 RPM. The car runs great otherwise but, this one issue really spoils the driving experience!
Sitting in the driveway, I can clearly see that the throttle lever on the front carb isn't returing fully closed. With the engine running, I can push the throttle lever back closed with my finger. It only moves about 1mm to close - and it feels like it "releases" almost like something is binding. Idle returns to 750 RPM.
Here's the baffling part - I inspected and checked everything mechanical and I lubed the shafts. With engine off, the throttle lever and throttle disc work perfectly and close fully. It is only when the engine is running that the problem manifests itself. To confirm this, while experiencing the problem (idle at 1,500 RPM), I killed the motor and could watch the throttle lever return that 1mm fully closed as the motor died. Then when I immediately restart the motor, it goes straight to a 750 RPM idle.
At this point, I can only think it is something vacuum related...but what?? I have a new cylinder head and manifold gaskets. Carbs just professionally rebuilt (carb body rebushed and new throttle shafts among other things). Engine has 180psi dry compression across all four cylinders and pulls 20"-22" Hg of vacuum at the intake manifold.
Any ideas?
Bob
I need some help. I spent all day yesterday trying to get my rebuilt carbs dialed-in (SU HS6s). What should have been a 2 hour job became a very frustrating all-day affair.
My issue is a hanging throttle. I got the carbs balanced, mixture set and idle at 750 RPM. But, if I slowly take the RPMs up and let off the gas (i.e. crusing and coming to a stop sign) it will hang at 1,500 to 2,000 RPM. If you snap the throttle, it will drop back to a nice 750 RPM. The car runs great otherwise but, this one issue really spoils the driving experience!
Sitting in the driveway, I can clearly see that the throttle lever on the front carb isn't returing fully closed. With the engine running, I can push the throttle lever back closed with my finger. It only moves about 1mm to close - and it feels like it "releases" almost like something is binding. Idle returns to 750 RPM.
Here's the baffling part - I inspected and checked everything mechanical and I lubed the shafts. With engine off, the throttle lever and throttle disc work perfectly and close fully. It is only when the engine is running that the problem manifests itself. To confirm this, while experiencing the problem (idle at 1,500 RPM), I killed the motor and could watch the throttle lever return that 1mm fully closed as the motor died. Then when I immediately restart the motor, it goes straight to a 750 RPM idle.
At this point, I can only think it is something vacuum related...but what?? I have a new cylinder head and manifold gaskets. Carbs just professionally rebuilt (carb body rebushed and new throttle shafts among other things). Engine has 180psi dry compression across all four cylinders and pulls 20"-22" Hg of vacuum at the intake manifold.
Any ideas?
Bob