I posted this on the injection/carb/etc. forum, but thought I would put it here too, just in case someone can help.

The carb (4160) on my 390 was in need of a rebuild (or so I hought). So I bought a kit and rebuilt it.

When I started the truck, it flooded immediately. After much troubleshooting" I discovered that the 'new' power valve was bad. I put my "known good spare" in and the flooding went away.

The engine starts and idles, but the idle speed is constantly varying between 700 and 900 rpm (sometimes as high as 1000rpm). Also, when I accelerate the engine in neutral, it misfires continuously out the exhaust, making snapping and popping sounds (I have Snap, Crackle, and Pop living in my exhaust pipes). If I attempt a rapid acceleration from idle in neutral, it will backfire out the carb intake.

The vacuum is now varying around 9.5 inches. It was at 13.5 before I did the rebuild. I've replaced the gaskets between the manifold and the spacer and between the spacer and the carb.

I've had the carb apart several times trying to find the problem. I even went so far as to put another 4160 together and try it. Same results as described above.

I bet I have "built" a hundred carbs in my life. But every now and again, one of them bites me in the b*** just to prove I ain't as smart as I pretend to be. I'm convinced that I had either missed something or have put in (or not put in)a part.

To me it seems to be running very lean.

I've changed the plugs, dist. cap and rotor, and the coil, with no luck.

I'm at a loss, and could sure use your help.

OldFords bad attitudes

 

quite simply, you have a vacuum leak. Where it is , is up to you to find. Use carb spray and spray all around the carb with the engine running. You will know when you have found the leak (s).