4100 base gasket
My 61 has 66-type spacer under the 4100 freshly rebuilt carburetor. This spacer has the front 2 holes partially connected and has a vacuum connection which I currently use for my vacuum advance which helps cooling by advancing timing at idle. I have Felpro 60059 4-hole gaskets above and below the spacer. I can find no vacuum leaks. I have a low rpm misfire usually noted when cold that now seems also to be present warm as well. The misfire seems to be reduced by turning in the idle mixture screws, to a point. These are currently at 1 1/4 turns. I noticed that the gasket under the carb is slightly abraided in the center, under the balance tube area, making me wonder if the gasket is interfering with whatever these tubes do. When I took the carb off the engine the carb base gasket was noted to be a homemade single hole affair, which makes me wonder if my 4-hole gasket is incorrect. I note with interest that the base gasket for the 1960 Bird with 352 engine appears to be the single hole type and wondered if perhaps my 61 was cobbled from leftover 1960 parts. FWIW, I also noticed recently when I was adjusting float levels that sometimes the front bowl level would be correct, then not. I can find no vacuum leaks but I have fixed several, beginning with a ruptured vacuum advance. The misfire began about the time the vacuum advance ruptured. I plan to replace the spacer with the correct 61 spacer and experiment with a single hole spacer under the carb. I will also replace the carb needles in case I damaged them in setting float levels. Any advice would be appreciated.