This past Airventure I had the opportunity to talk with Hal Stockman (the Zipper big bore guy) and he shared with me his latest modification to the 912 engines.


He is removing the small balance tube between the intake manifolds and replacing it with a 1" diameter tube.

I just did this modification to my engine this past weekend and had the chance to test run the engine today. All I can say is WOW! What a difference this makes. The engine is now butter smooth from 1500 to 6000 rpm. A mechanical sync is all I did on reassembly and don't plan to do any more. This mod is something I've been thinking about for a long while, but didn't have the courage to do without a second opinion. Makes perfect sense to me and makes me wonder why these engines don't come this way from the start.

I forgot to snap a photo, but will do this tomorrow for the record.