Just installed dual 40mm Kadrons on a 1776 to replace Weber 34's. Runs smoothly, but when I take my foot off the gas, or when the motor is idling after warmup, there is a high pitched, and very loud whistling at the manifold area. When I removed the Weber, I carefully scraped away all the old gasket, *however*, there was a bit of the gasket (about the size of a quarter of a penny), which I cleaned off with a razor as best I could. Unfortunately, there remained a paper thin layer of the old gasket (no more than 1/8" square) which I could not get to. I put a new gasket on, bolted on the manifold and carburetor.
Any ideas? Could such a small possible air leak cause this noise? BTW, replaced the pulley and fan belt also, the deflection between the upper and lower pulleys is 1/4". Could it be too tight, causing the bearings in the alternator to make this whistling noise? I kind of doubt it because the noise disappears if I accelerate, and comes back on deceleration and at idle.