Sportomatic Control Valve Adjusting Screw

[Sharkbitemarky]

Sportomatic Control Valve Adjusting Screw Intermediate Pressure - So yesterday while checking for vacuum leak/s in the clutch vacuum system.

After finding a slight leak caused by a loose hose clamp on the 1 way/check valve, I did the following checks to confirm I had found all the leaks:


I connected a vacuum pump to the hose to the Airbox 1 way/check valve and started engine from idle the vac was about 15 inch Hg and when plipped max'd out at 20 inch Hg and held these vacuums this confirming that 1). The engine can generate the required vacuum and 2). The 1 way/check valve was working. Next I T'd in to the 1 way valve hose and the control valve (easy to do and do not need to lower engine...), using either my hand vac pump or the engine vac the maximum vac that could be achieved was 15 inch Hg ! no leaks, when changing gear it would momentarily drop to 10 inch Hg then increase again to 15 inch Hg.

Am I correct in thinking this limitation of 15 inch Hg is limited by the the Control Valve Adjustment screw.

Whats not clear to me is:

i) how does this relate to the 10 inch Hg I see after a gear change and the so called "Intermediate Pressure" ?

and

ii) What impact does the adjusting screw have and how is it adjusted ?

Cheers
Mark