[logician]

When I measure the airflow on my '73 911S (MFI) with a synchrometer, I find that the airflow at each of the left stacks is pretty much 75% if the flow at the right hand stacks. So for example, at 2700 RPM, all three right hand stacks read 16, while the left hand stacks read 12. At 730RPM, the left hand stacks read 3.5, while the right hand stacks read 5. The left hand mixture screws are all set at approximately 3/2 turns, while the right hand ones are set at approxmiately 1 turn. Another observation is that the left hand stack -- the one with the lower airflow -- seems to pop at idle and also at 2700RPM.

So my question is what might cause this difference between all of the left stacks vs. all of the right stacks? The throttle bodies are separate, each with separate stops, so you would think that any error would apply randomly to the cylinders, and not apply equally to all of the cylinders on one side. The throttles are all on their stops at idle, so I don't think it's that one side is getting more throttle than the other due to the linkage from the cross shaft.

The one thing that all of the cylinders on each side have in common is the cam. If the cam is timed wrong, could that cause a 25% difference in airflow? Any other ideas? Thanks in advance for any help.

-Juan