mustang dies after warm-up

I have a 1966 mustang six cyl- 200 ci that dies after warm up. Replaced points, dist cap, wires. Runs great for 10 minutes then sputters a bit. Could it be vapor lock? Has new fuel line from tank to pump. Still has small original fuel line to carb. Also has a whistle at certain engine RPMS.
Any help would be appreciated.

Jim

Was it o.k. before the points were replaced? If so, recheck the dwell (or no meter: gap) as timing will change and can cause hot vrs. cold idle issues.

Otherwise if this problem is ongoing I would look into a lean fuel issue next. The noise could be related to a vaccum leak as well. Don't forget that the choke enriches the mixture until the engine warms up.

With the engine running try partly restricting (with the air cleaner off, any vac.lines plugged off) the inlet of the carb. Playing with the ammount of restriction you're giving it, see how the engine responds. If you can find a sweet spot where it levels out and idles fine then you need to look into why it's running lean.

My bet is you're going to notice an improvement in hot idle because it idles good when cold. Look carefully for any source of vaccum leaks. If all is good then you've got a carb. issue. If you're comfortable with it try an initial mixture adjustment. I can't see a rebuild being required since most problems caused rich/flooding issues.

Thanks for the reply,

It was doing the same thing. I think I got the gap pretty close. It ran much better even cold after I replaced points and cap. I also loosened the valves on cylinder 1 because it apparently was stuck open. After I did that I could detect changes when I would remove/replace the spark plug wire on it.

Could it be that I have the electric choke wound/turned too far and it is leaning out when it gets hot?

Good to see you did a power balance check, just watch out for the Zaps! ;)

I would think the choke operation is good since it runs o.k. cold. If the choke was set too rich or too lean it would only affect operation when cold anyway (if it opens fully when hot).

Visually you can check its operation looking at the choke flap at the top of the carb. With engine cold, remove the air cleaner cover and activate the throttle with your hand. You will see and hear the flap close fully if cold (<60^f ?) enough. Push your finger on the lower side of the closed flap and you can feel the spring tension its under. The spring is bi-metallic and changes its state with temperature. A hot engine results in the springs tension actually holding the flap open.

After the car is started the flap needs to open a little or the engine will stall out (too rich). This "unloading" of the choke is done by the vacuum operated choke "pull-off". Looking closely you can see it mounted on the side of the carb with a vacuum line and linkage leading to the choke flap.

Telling you to try covering the carb air intake when the engine is "hot" is a quick way to find out if the engine is too rich or too lean. From what I told you about the choke flap you can kill the rag idea and instead manipulate the choke flap directly with your fingers while the engine's running.

If the idle improves that shows the engine's lean when hot. Too much air, insufficient fuel. Post back what you discover.