Today, it finally clicked and I’ve figured out the tuning secrets of the Borla EightStack. I knew how important the linkage settings are and how sensitive they are. I was spending all my time to get the idle right but had overlooked the importance of checking at higher RPM’s. With a little trepidation, I set the RPM to 3,000 and checked the airfow. One side was 11, the other side was 18. Obviously, the cross-linkage was off. But why, it was OK at idle. Then I realized at idle, some of the blades may be resting on the venturi bores and unloading the linkage. 

I adjusted the cross linkage at the higher RPM (remember, it’s very sensitive) and after a couple tries, SUCCESS! My cross balance airflow matched at idle, 2000 rpm, 3000 rpm and 3500 rpm (Chickened out for the higher settings)

The secret – do the final linkage tune at higher RPM’s and have to guts to let the engine run up higher while you’re adjusting it.

There are some posts out there telling you to use only one throttle screw on the Borla & Weber systems – the cross linkage will position the opposite side accordingly. THIS IS NOT CORRECT. The cross-linkage must be set so as soon as the blades come off the throttle stops, they are in Sync : Thus the setting at higher RPM. But while on idle, the left and right bank must have their own idle stops since the linkage and the venturi bores/blades don’t play well together. By having individual idle stops on each side, the tolerance accumulation is minimized and the motor will idle much smoother.

So happy with the results, I posted more details in the engine section. I will continue to update the Borla EightStack saga as I sort it out.