My R&D budget for home made venturis might need to be increased if I'm going to get that engine to run on suction. So far I've got 50 cents invested in aluminum, most of it ended up on the floor
. I wonder if a long stack would permit the large diameter air intake but still develope better suction? A more convoluted approach would be like what is done on a Holley, have a booster venturi [like a brass tube] stationed inside the larger, main venturi. The fuel gets fed into the inner [booster] venturi, and the vacuum signal there is very strong.