Sportomatic - Drop in rpm's when a gear is selected

[TRACKS]

Hi All -

The resurrection process continue on my '74. ( Sportomatic )
Engine is running very good. Brakes are good.
Heres the issue :
I noticed that the car is idling around 1000 but when i put it in gear, the RPMs drop to around 300 ( or less ). Amazingly, the engine continues to run in gear with my foot on the brake.
The tires that are on the car are 35 years old so I haven't driven the car out on the road yet to see how the Sportomatic transmission actually shifts but I am able to put the car through all the gears while my foot is on the brake.

thanks
Kevin

[72_sporto]

Hi Kevin, There is normally a drop of several hundred RPM when in gear but yours seems a bit high. Have you checked the 2 non-return valves are sealing- I'm assuming you have already checked for leaks in the hoses? Cheers.

[72_sporto]

An update to this...

I recently put a temporary 75 2.7CIS into my 72 sporto and had exactly the same problem- only mine was actually dying. At first, the motor was running fine after the change but started dying after I discovered the airbox clamps were loose and tightened them up! Long story short- It turned out to be running rich after getting full vacuum again. Backed off the mixture 1/8 turn and it's now running sweetly.

[TRACKS]

thanks 72_sporto - I will check that out the next time i get back to working on the car !
btw, the car is running really good now, but i know i still have a significant drop in RPM when putting it into gear.
Out on the road , it shifts great.
thanks for the suggestion,
Kevin

[72_sporto]

Hi Kevin, If it's "thudding" into gear when you are at idle - ie, almost dying, then recovering - you may need to have a look at the control valve. The valve is designed to "cushion" the change when the throttle cam follower is at idle and is fully extended. The rush of air from the diaphragm de-clutching is meant to be restricted.

[cpa]

Don't forget you have a torque converter involved. The drop in RPM is due to the drag from the converter. As long as the idle is still smooth and even. The converter is also the reason you can leave it in gear at a stop with your foot on the break.