So I want to retract what I've said previously about setting idle mixture. I have discovered the vacuum gauge, and for me it's the best tool there is for tuning idle mixture on the carb. Here's the one I have.
http://www.harborfreight.com/cpi/ctaf/d ... mber=93547
Probably the older guys on here know how to tune with a vacuum gauge, I am just learning but now I know I have my carb set up right. I started with the initial 3 turns out setting on the mixture screw. It ran like crap and the vac gauge showed a low reading. Richened it up until I got maximum vacuum, idles a lot better than when I was guessing at the right mixture. Then I revved to 2000 RPM, I was getting like 20" vacuum with a steady needle, which is awesome. At idle, the needle vibrates, but not too much I'd say between a half inch and inch of vacuum. I may investigate valve lash or sticking valves, but it's OK for now. I have one valve that's making noise, I bet if I tighten it up a bit that might help.
From what I've read the vacuum gauge can be used in the following ways;
-set idle mixture
-set ignition advance
-diagnose sticking valves
-diagnose gross vacuum leaks
-check ported vacuum
-diagnose clogged muffler
and a host of others, there are many threads on the net for it. I like this method because you know that when you get maximum vacuum, you're at about optimum on your mixture. This means I can easily re-tune when I put my Offenhauser manifold on, because it'll likely flow a little more air than stock so I'll need to richen up.
Login
FAQ
Search
