Correct air flow number, MFI Synchcrometer

[caproader]

Guys,
I bought a new toy (Synchrometer Flowmeter) and am now trying to put it to good use.

On a 73 2.7 with MFI:

1. Is there an optimum number at idle that I should shoot for on the Synchrometer scale of 1-30? Or should I work towards getting all 6 stacks to synch to one specific stack? If so is there a reference stack that I should work from? Right now the right side stacks are showing around 7 and the left side stacks are around 5.

2. When I am turning the idle adjustment screw, does turning the screw 'in' (Clockwise) make the Synchro numbers get higher or lower? So far, turning the screw as much as 720 degrees in either direction doesn't seem to make much of a difference. Do I need to blip the throttle after each stack adjustment to notice any change? It seems to me that turning the adjustment screw 'out' would increase the number as more air is sent through the bypass. Or is the answer to questions 3 required before I start adjusting?

3. Do the adjustments need to be made with all linkage balls popped off?

Thanks for the help. Note to Ed Mayo: Enjoyed the conversation with you in Charlotte, hope to get together again some day.

John,
Card carrying member # 322
73 S with sporto, 73 2.7 mfi and 69 912

[PStey]

1. All stacks should be the same. As the right side pulls more air you should check if the cross bar properly adjusted (are the right side throttle valves at their stops when the left is?). Mine shows approx 4.5 on all stacks. Have you measured with all linkages removed?

2. Turning the screw clockwise (in) closes the air passage which bypasses the throttle valve. So turning in will lower the measurement. These passages will get blocked with carbon rendering them inactive. Clean them first. On mine, the measurement responds significantly to adjustemt of the screw.

You should not need to blip the throttle, the effect should show immediately


3. Do the adjustments need to be made with all linkage balls popped off? You should make sure that the rods between the throttle valves are adjusted so that all valves are at their stops. Once this is the case, it does not matter if you measure with or without them.

[304065]

A 7 is pretty high for idle.

Of course you should follow Check Measure Adjust and make sure your ignition timing is correct BEFORE trying to set the idle. If the timing is too far advanced you will have too high an RPM and it will try to jump up at the slightest provocation. For setting correlation you just need to hold an idle, so you might even consider slightly retarding it so that it doesn't jump up on you when you're trying to make adjustments.

You SHOULD be able to remove all the linkage rods (don't mix them up!), set all the air corrector screws OPEN THREE half-turns (for a 2,4 or 2,7) and have the car idle at a solid 900 rpm, then take the average value from all six stacks. If you have:

III-6...VI-7
II-6.....V-7
I-6.... III-7

then the average is 6.5, you should be able to turn the air corrector screw in or out to get that reading. If you have any air corrector open more than EIGHT half-turns, that channel is carboned and must be cleaned out. Don't overtighten the air corrector screws.

[caproader]

John and Peter,

Thanks for the good thoughts and advice. So far I have only taken a reading to see what I have. Now it looks like it is time to get serious using your good directions. The stacks were rebuilt about a year ago by Matt Blast so except for a short period when the hose from the heat exchanger fell off and the car ran incrediably rich, the passages should be clean. Maybe I need to remove the idle adjust screws and blow some carb cleaner through.

Thanks again for the help. This should give me a project for the coming week end.

John