R-1 Carb Throttle Dashpot

[Paul K.]

I do not have my service manual with me and am wondering what the carb throttle dashpot does on my 63 R1, Auto, non-A/C Avanti. Right now it pulsates back and forth when the engine is running making an unstable idle so I know I need a new one, but it seems to work in the opposite way compared to others I have seen before. When the engine is off or no vacuum, the dashpot is extended holding the throttle open. The opposite is when the engine ir running - throttle closed on the idle stop. Is this to provide a slightly open throttle to help starting? Right now I have it removed so as to tune the engine which was just installed and the car idles and starts fine. Are these still available and are they necessary?

[PackardV8]

FWIW, I don't remember seeing a throttle dashpot on a non-AC R1. Might have been there, but I don't remember it. In fact, the only one I have from an R1 is a combination electric/vacuum - a Service Bulletin item on AC cars to increase the idle speed when the AC was on.

Is yours electric, vacuum or combination?

In general, throttle dashpots operate in various ways:

1. As mentioned above, wired with the AC to function as a "throttle kicker" to maintain proper idle when AC is on.

2. The later GM throttle kickers were just the opposite. They functioned as the operating idle stop and maintained an idle speed when on, but when the ignition was shut off, they retracted and closed the throttle completely to prevent run-on. Run-on was a problem with the band-aid carb and ignition tuning the OEMs were trying to meet emissions without spending the necessary money for EFI and computers. Didn't work, obviously.

3. To slow the return of the throttle when the accelerator pedal is released. Again, lame emissions tuning.

jack vines

[Paul K.]

Mine is vacuum only and is attached to the base of the carb with a one bolt bracket. It gets its vacuum from the T on the manifold behinf the carb. Pretty sure its correct original as the motor had never been out of the car and it had been parked since '72.

[Guest dapy]

Paul,

Did you have your R1 engine rebuilt? Like to hear more about that.

I have gotten helpful and timely answers from Jon Myers. He rebuilds Avanti carbs, engines and superchargers. Very knowledgeable.

[Paul K.]

No, I didnt rebuild it, as it had even compression, good oil pressure, 18" of vacuum and ran perfect. It just had a some oil keaks and needed the water jackets cleaned out. I felt it was just easier to do it out of the car.

[PackardV8]

Did you have your R1 engine rebuilt? Like to hear more about that.

I've rebuilt several Studebaker V8s, some of them R1s. They're 99% like any other OHV8, but that 1% will trip up shops which don't do them regularly. The decision points to make:

1. Stock or modified? Have to appear original for judging or want the best performance?

2. Are you having trouble with pinging or enough of a CASO to want to run regular gas? OEM R1 flat top pistons, semi-dished or OEM 225hp dished pistons are some of the options.

3. Stock rear axle ratio or overdrive transmission?

jack vines

[brad]

The dashpot is more to prevent stalling upping the idle. If it is surging, it is usualy because it is trying to stall, and loosing vacuum enough to make it kick in.

I had this exact thing happen on a customers car, it turns out the idle speed was set so low that it was trying to die at idle, but the dashpot would kick in preventing it. This caused a wierd surging loping idle. Turn up the idle speed screw (not the mixture screws).

[Paul K.]

Yes, but this one appears to work in the opposite fashion. It extends and holds pressure against the throttle when the engine is OFF. The car operates fine with it removed. Still curious what it actually is supposed to do.