Got A Miss . . .

[grey beard]

My motor starts and runs like Walter P. wanted every engine to sart and run. Soundds like a Swiss watch. Pulls fine on hills and goes down the road right sweetly . . . . . . UNTIL I get up to about 2000 - 2500 RPM, then it begins to break up and miss. Will NOT go above this engine speed.

So far, I've tried adjustinmg the points, played with the timing a little, pulled the distributor and checked the ground wire on the breaker plate and checked the vacuum advance uinit, disconnected my pcv system, and scratched my head alot. Still no joy.

This engine ran fine AND ran up to the top speed just fine before the major overhaul. Overhauled the carb, everything in the ignition system is brand-splimter-new. I'm about ready to pull the carb apart again to see if something there is unhappy.

Any advice, local wisdom or suggestions of a practical nature? There's not a nicer starting and running engine around, UNTIL I raise the speed to the top third of the rpm band.

Mebby it's gremlins .. . . . . mebby they hate me .. . . . .

[Young Ed]

When I was having trouble with this we wired a small light bulb I believe off the coil to see if it was an ignition issue or something else. Mine turned out to be a bad vacuum advance.

[Tom Skinner]

Young Ed has a good point, another thing, if the float height isn't right in the carb, or the carb linkage has been bent somehow.

One more check - is your automatic choke set right?

Vacumn at 20"-21" steady hand?

Tom

[grey beard]

B series rrucks all use manual cable chokes, even below the equator in Down-Underland.

[Merle Coggins]

Even with a manual choke, it may be worth checking to be sure it's fully open.

To me it sounds like it's running out of gas. If the ignition system checks out, my next check would be the fuel supply. If you can achieve the higher RPMs under no load, but it stumbles under load, that indicates that it's not getting enough fuel to keep up with the demand.

Merle

[red48b1c]

I'd think about replacing the condensor. I had the same symptoms on a car one time, and it took me forever to figure out the condensor was the problem.

[grey beard]

Merle,

Stumbles and carries on with no load, sitting in my shop. Simply will not go over 3/4 throttle speed. Clean tank, new electric fuel pump, new line. Methinks it gotta' be the condenser or somehing inside the carburetor. Sure whsih I knew what it is.

[Don Coatney]

To me it sounds like it's running out of gas.

Merle

If it is running out of gas the engine would simply quit running. It sounds like it is still running but miss firing.

How is the spring tension on the points? How is the condition is the point cam inside the distributor? Do you have another distributor you can drop in it for a test run?

[bkahler]

If it is running out of gas the engine would simply quit running. It sounds like it is still running but miss firing.

Don, I'm not sure I would agree with this statement. There is a good possibility the fuel flow is not sufficient to keep the engine running at full speed. My wife's race car has done this same thing when she reaches the upper RPM range (8,000). In her case it was related to carburetor float levels being incorrect (blame me I'm her chief mechanic ).

In Grey Beard's case it could be fuel filter, partially plugged fuel line, weak fuel pump, etc.

How is the spring tension on the points? How is the condition is the point cam inside the distributor? Do you have another distributor you can drop in it for a test run?

As someone mentioned earlier the condenser could be suspect. I'm not overly thrilled with the quality of the aftermarket condensers. Something cheap and easy to replace to see if it helps.

Brad

[wallytoo]

If it is running out of gas the engine would simply quit running. It sounds like it is still running but miss firing.

not necessarily. inadequate fuel flow could manifest itself as a stumble at a certain rpm. even with w-o-t, there'd only be enough fuel available to run at lower rpm, which would result in a miss/stumble, until a little more fuel made its way into the carb. i've had precisely that problem, when the float was set too low. whenever i "got on it", it would run ok, until the bowl emptied, then it would stumble/sputter, but it didn't die.

a sight-glass would be nice on the old carb bowl, like some holley's have, then you'd know whether it was a fuel starvation issue, vs. a plugged carb passageway.

[grey beard]

Gents,

I'm going to pull the carb top and run it, and actually look at the float bowl level to observe just what's happening. My brother, a life-long mechnic, listened to the problem and drove the truck, and said, "It's electrical - too sudden to be fuel."

We'll soon see. I'll let you know what I find. First time for me on a problem of this nature, and I've been in the business 45 years. Wow! That's a long time. Why, I'm almost a fossil. Go figger . . . . . .