Columbia Vacuum Control Valve Adjustment

[glennpm]

Hi,

I'd like some help please in how to properly adjust the clutch pedal to Columbia Two Speed vacuum control rod. I've read the various available articles but it is still not clear to me.

The control valve I have is shown in the second image below.

The first article from http://www.flatheadv8.org/columbia/columbia1.htm
says this:


"CLUTCH PEDAL VALVE ADJUSTMENT.

With clutch pedal down against floor board, adjust the adjustable clevis on link of clutch pedal valve so the line of the valve piston is flush with the face of the valve as indicated by letter "K" in General Diagram. Tighten lock nut against clevis."


The reference to "... letter "K" in General Diagram" is confusing. I have attached this reference in the first attached picture. I am wondering if this really means that the bottom of the piston skirt should be even with the thick part of the vacuum case as I've marked in the attached picture, "Limit of Piston Travel.jpg"

From another article, "http://www.flatheadv8.org/columbia/columbia2.htm", says,


"ADJUSTMENT:- Control Valve Clutch Connection – Adjust clevis on valve operating rod at control valve end so that valve plunger
is depressed 1/8" minimum, ¼" maximum with clutch pedal depressed to floor. Valve travel must not exceed ¼"."


This would agree with my interpretation of the maximum travel. If my piston skirt is flush with the casing protrusion, it would still be less than the maximum 1/4" of travel."


But there are also this adjustment warnings from the first article above,


"THIS ADJUSTMENT IS IMPORTANT.

To obtain a proper shift in the Two-Speed axle, depends largely on the timing of the clutch pedal valve opening with the engine clutch disengagement.

THE VALVE MUST NOT OPEN UNTIL THE ENGINE CLUTCH IS COMPLETELY DISENGAGEMENT. To check the correct valve timing, set selector lever on dash in neutral position. Move transmission shift toward first gear until the gears just start rubbing, declutch slowly till gears stop turning. The clutch is now disengaged. Continue declutching slowly until air is heard passing through selector valve, indicating opening of pedal valve.
There should be ½" minimum clutch pedal travel from disengagement of clutch to the opening of the valve. If necessary readjust engine clutch."


The first paragraph is telling you to find the declutch point. I guess I would do it differently. I would push the clutch pedal to the floor, shift into first, then slowly release the clutch until I could feel gear engagement and the car starts to move. It also sounds like the vacuum hose should be disconnected so you can hear or feel air being sucked in the open hose.



Is the downward movement of the control valve piston not to start moving until the declutch point?


How have you adjusted your Columbia vacuum control valve to clutch pedal arm?



Glenn

[jimTN]

I have one of those main valves but not the clutch valve. I have set up several 46-8 systems with the Crosley brake switch to the clutch pedal and the operating principle is to kick the system down to low range when you push the clutch in. This is so that when you come to a stop, you will start out in low range. That is why the clutch should be disengaged so the system will shift and in reality, the transmission would also be out of gear at the same time.

[glennpm]

Thanks Jim,

Pending other responses, I think I'll measure the stroke while I have help depressing the clutch. My guess is about 3/4". Using this, I'll gap the clearance with clevis rod adjustment, between the actuating lever and the clutch valve piston so that I get 3/16" after the lever is able to push the piston down.

[Terry,OH]

For the diagram you have shown, On the rod K is an machined line. You adjust so the line is at the end of the housing. That clutch valve in your diagram is used for the 35-36 Columbia. Your valve is for the 37-41 Columbia. Adjust clevis on the operating rod so the lever depresses plunger in valve at least 1/8" but not more than 1/4" when clutch is depressed to the floor.

[glennpm]

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Thanks Terry!