Troubleshooting this problem has gotten a little tricky, so I thought I'd see if you guys could think of some angles I haven't covered to sort it out quickly.



the background: re-ringed the engine very recently. I initially ran it from a gas can assuming the tank to be full of rust and debris. The tank had had a few gallons of very old gas in it. It was so old that the engine would die rather than burn it. I drained that gas and inspected the tank through the sender hole; it appears to have some kind of liner inside of it but no sediment. I put about 6 gallons of new gas in the empty tank and hooked it up to the fuel pump with a filter before the pump. It ran great, would idle very low very smoothly. Having set the ignition up the way I wanted, I was going to rebuild the carb, but though it ran fine, the fuel smell at the carb smelled more like old gas than new gas. So, rather than rebuild the carb just to potentially gum it up, I decided to fill the tank with fresh gas and a can of gas treatment and dilute the residual fuel varnish out. Once I smelled the right fuel smell at the carb, I'd go ahead and rebuild.



I moved my attention on to sorting out other minor issues, which involved a lot of test drives within the neighborhood (as I didn't have the car registered yet). One day, as I'm returning home to park, the engine starts struggling to maintain idle in gear. It has been this way ever since. I have to hold the throttle up to keep from stalling, and even the idle in neutral or park is not the buttery smooth thing it once was.



Things I've checked: 1. The ignition settings. Dwell angle is 27, initial advance is 6, same as when all was well. I watched a timing light strobe with the pickup on the coil wire while idling to see if spark hiccups correlated to engine hiccups, but there was no irregularity in the spark signal. Consequently, I don't think this is an ignition problem.

2. vacuum leaks: I sprayed water all over the manifold gaskets, carb gaskets, and throttle shafts looking for a change in running or the telltale slurping noise of a leak, but none has turned up.

3. Carburetor: it's a Carter AFB so there's no power valve or secondary idle circuit. I took the carb fully apart and went through all of the passages and adjustments. I found no debris or blockages. Special care was given to the idle circuit. No improvement came of this.

4. Valve adjustment: set at .020 cold.



Other observations/notes: When I took the carb off yesterday for cleaning, the intake passages were lined with a tacky varnish which was not present inside the carb but was present on the underside of the throttle plates. Before the test drive that ended with this problem, I made two adjustments: I adjusted the dwell from 25 to 27, and I turned the idle mixture from 2+ turns out to about 1.25 turns out. Last time I had checked the mixture adjustment it had not been possible to run the engine at 1.25 turns; I attributed this change to the fresh new gas working its way through.



Sorry this post is so long, but I like to cover the scenario as clearly as possible. Now, my theory: I am wondering whether this mysterious 'Valucraft Gas Treatment' I added might be the cause of my problem. The product literally did not indicate what its intended use was or in what way it treated the gas. Someone gave it to me one day and I assumed it was for stabilizing fuel so that it would not gum up over longer storage. I added it thinking it might help clean up the fuel tank. Since reinstalling the carb, I found I had to turn the mixture screws out to around 2 turns again to get the best idle, which is not nearly as good as it used to be. There are two things I want to try: 1. running the engine from a can of fresh gas and 2. putting a vacuum gauge on the intake pre-vacuum-pump to look for signs of mechanical mischief.



Can you think of anything else I could be dealing with here?

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive