Chester_Kaup

I have a 1966 mustang 289 with a C4 automatic. The carburetor is an Autolite C5ZF-F mounted on a ford 4 barrel intake. The engine was running very rich to the point of spitting chunks of carbon out the exhaust. I tried to reset the float level to the .906 wet setting but could not get it quite that low. It was still running rich so I changed to the jets from a 48 to a 46 on the primary and from a 58 to 56 on the secondary. Now my troubles.


1. When I start the car with the engine cold it will not keep running without making several attempts and revving up the engine. It then seems to idle a bit slow. Choke appears to be operating properly. Did I lean it out to much? Used to start up and keep running.


2. The engine idles roughly. Changed out the plug wires to another set I had with no noticeable difference. The rotor and cap are new. I find no vacuum leaks .


3. I noticed after I shut off the engine that fuel on the primary side of the carburetor was going into the engine.


Any help would be appreciated.

Chester_Kaup

Problems 1 and 3 solved by resetting floats to dry specification and putting stock jets back into the carburetor.


Problem 3 remains unsolved. Are there errors that can be made rebuilding the carburetor that would cause a rough idle?


Thanks

Starfury

#3 is concerning. Where is the fuel going? Do you maybe have a blown power valve?

Chester_Kaup

I made a mistake in my reply. It is issue 2 that remains unresolved. Sorry about that and thinks for any help.

rmodel65

are you running the 289/302 firing order cam or a 5.0/351w cam firing order?

Chester_Kaup

I have verified numerous times that I am using the 289 firing order. I doubt that the reputable engine rebuilder would have used the wrong cam. Thanks for the idea.

Mark Hone

Power valve would be my guess. M.

rmodel65

a lot of people go to the 351w firing order because it is a better order to use for reduced engine harmonics etc

Chester_Kaup

I tried the 351W firing order and the engine started right up and run until it warned up but when the idle dropped it stalled. It also backfired when accelerating in park.

boogerschnot

Have you checked the fast idle cam for the choke? It should have two idle settings. When the choke is engages the idle will be higher, not just from the closing of the choke but from the butterflies being cracked a little more using the fast idle cam.