I started my 73 F100, 390 this morning and pulled out of my driveway. I let it warm up, let oil Pressure rise, everything. Got down the driveway and pulled into traffic. Upon acceleration, I got up to about 20 mph and had NOOOO power--nothing, like the motor was trying to die. It then recovered and went on just fine. I am going to be addressing an exhaust leak issue soon, but need to know what this problem is. Living in a blind curve on a well traveled road isn't too much fun in the mornings. It only seems to do it in the mornings, never happens through the rest of the day. Any help would be awesome.

 

Without more info best guess is a fuel supply problem.
When you can, dig into it and see what you find. Let us know, we'll help all we can.

 

It only does it on cold starts. Could it be carb related? Just need to know where to start looking on this beast.

 

Automatic choke sticking shut, thereby flooding the engine??? I know that is a stretch this summer.

Fuel filters clean?

Carb need cleaning and rebuilding?

Just a few ideas.

Robert

 

How long did you let it warm up?
If it was still cold (intake wise) and the choke wasn't closed, it could have been a flat spot in accelleration caused by a lean mixture (choke open before its warmed up).

 

I let it warm up for about 5 minutes or so. Should I be revving the motor or something during warmup? It's going to a shop on Thursday.

 

I wouldn't rev it up but it sounds like a choke that's either not closing or opening way too quick. Another item people overlook now days is the heat riser valve on the drivers side exhaust manifold. When the engine is cold this valve is closed and forces exhaust gas to flow through the intake manifold below the carb. This aids cold start warm up. It's common, real common for these valves to sieze in the open position and not force the heat up under the carb.

 

Agreed, with the engine cold, start it up with the air cleaner off and watch how long it takes the choke to open up. You're running lean most likely because the choke is set up incorrectly.

 

If you have a working temperature gauge it should help you know when its warmed up. Any backfiring?

 

Temp gauge works, it's in the middle when I decide to take off on the road...

I'll start it up with the air cleaner off in the morning and watch the choke. My dad said that some folks used to do something to disable the choke on some of these motors...I dunno...He also said that he had a 390 that was kinda sketchy back in the day when it was brand new and it always took "a good warming up" in the morning for it to run properly.

I put a can of seafoam in the fuel tank, filled it up, and drove it around the Loop 10 (a pseudo-highway/interstate thing that encircles Athens) after that was suggested to me by the mechanic I have it scheduled to see on Thursday. He said that sometimes seafoam will clean out the fuel system and sometimes it will loosen up a crudded up carburetor as well and it might not need to even be seen...we shall see in the morning.

I have no clue how to adjust a carb--I did say this truck was going to have a learning curve.

 

Started the truck up this morning. I took the air cleaner cover off, the choke was closed before startup. After 3 minutes of running, the choke was all the way open and the engine was still on the cold side. Could the choke be opening way too fast, and if so, is there a way to adjust it?

 

No backfiring btw.

 

The choke housing has 7 "notches" along the top; one in the center; three going toward the back, and three going toward the front. There is a small slit on the outer diameter of the black choke cap. Is this slit lined up near one of the notches? If so, which one?

3 minutes during the summer in Georgia doesn't sound too bad. It's possible you have a pre-existing lean condition or vacuum issue that's exacerbated at cold temperatures. Have you hooked up a vacuum gauge when the engine is warm?

 

Another thing the OP needs to check is the heat riser valve. If this is stuck in the open position, warm up will take a lot longer even though the temp gauge is reading warm.
It's located on the exhaust manifold on the drivers side.

 

Here's the choke adjustment fmc400 was talking about. This is a 1 bbl. but the housing is the same.