Help! Newly installed 200 sputters out at 50mph every time.

Good evening guys. Been working on a old 65 van I found sitting in a field last summer. I installed a 66 200ci out of a 66 Mustang with only 80k on it. It has a Motorcraft carb (Holly1940) and everything else is stock. Starts and idles great. Runs up to 50 no problem then hits a wall. I back of the gas and it smooths back out. If I punch it trying to get past 50 it just sounds like Im sucking air. It has a new electric fuel pump and I checked distributor advance and both seem fine. Any ideas would be greatly appreciated. This is a manual 3 on the tree. Thanks in advance.

when you step all the way down on the gas pedal,,,,,is the throttle plate in the carb fully opened?

It seems to be. I only see gas squirting out of one jet on the drivers side of the carb. Im going to readjust the carb and ground the block and see if that helps. Thank you.

Check the float level make sure it isn't set to low. Will it rev OK? New fuel filter? Maybe the sock on the fuel sender pickup is partially plugged, crud in the tank. It sounds like it's running out of gas

Seth. I had the tank cleaned before I installed it and put on new sending unit. Also have a fuel filter before fuel pump and a glass one before carb. I do see small pieces of debris in glass filter but very small and very few. Could timing act like this and get worse as distributor advances? I havent set timing with a gun yet, just a glass of water on the air cleaner. Ha!

It could be an ignition issue. I would lean towards the coil b/c it you say it starts runs and idles well. Maybe bad ground or bad coil. You could put some vacuum on the diaphragm and see if it is moving as it should in the distributor.

Maybe there is a chance that the breaker plate looses its ground ,,,,try running it with the vacuum line unhooked and see what happens,,,,,,

Tried running without vacuum line on distributor, changed condenser, cap, plug wires, adjusted points, set timing to 8 degrees and still seems to have a governor on it. Its just like the old go carts at a public track, just wont go past 50. My friend that helped me tonight swears it has a governor on it because it runs so smooth. I even red lined it first and second gear and it keeps pulling. As soon as you hit third and get it up to 50, starts coughing. Gonna limp it down and get new exhaust put on tomorrow and see if that helps. Current muffler sat for 20 years, could have a rat nest in it. Ant reason not to run a Flowmaster with 1 inlet and 2 outlets running out in front of each rear wheel?

Coil! Got it, Ill try that tomorrow. Thanks Seth.

You may be onto something with the plugged muffler hypothesis. It's an odd problem you're having.

Ok, did the exhaust and got no love. Looks and sounds sick though. Im going to test coil tonight but im thinking about just going electronic while im messing with it. I made an appointment to get carb looked at on Monday. Also going to go back and look at all fuel lines from tank to carb. Thanks for the help, Ill keep ya posted.

run a clear line in or from fuel pump to carb,,,,,,,see if gas flow changes when problem shows up for a test,,,,,

Ok, Ill try that on Saturday. How important is it to run the same size fuel line from tank to carb? I ran new 5/16 rubber fuel line from carb down the dog house to about 1 foot behind the drivers seat and reattached it to existing hard pipe. I also added a glass fuel filter about 3 inches before the carb inlet. The gas seems to only be about 1/3 or less full in the fuel filter while running around 45 mph. I also blew out the existing line before using it and currently have 1 bottle of sea foam in the tank for good measure.

that would be a test,,,,,,,take that filter off and replace it with rubber or clear plastic in a loop would show you if gas is not flowing enough at high speed,,,,,,,you say you found stuff in that filter,,,,,,that stuff came from the fuel pump,,,,,,,is there an actual filter in there,,,,have you cleaned out the carb?

Ok, Im going to pull it out and give it a run. Thank you.

you still need to try and see if its a spark or fuel problem,,,,,,I am not too impressed with Fords loadamatic distributors and spark valves,,,,,so maybe another fuel test is to run the van and when the problem happens,,,shoot some carb cleaner into the carb through a vacuum line or loose air cleaner just to see if engine acts better with that shot of carb juice,,,,,which is adding more fuel to the system,,,,,,watch out just in case the carb backfires ,,,,,dont be looking down the carb with the air cleaner off  when the engine is chugging and you are spraying carb cleaner down it,,,,,,any vacuum line will suck the carb cleaner into the intake for this test,,,,,,PCV line would work,,,,,,

Ok, that sounds like a good test. Ill do that first thing in the am before work. I understand what you mean, that way I will know if its getting spark or not. If its not getting proper spark, should I go with Petronix? style or a full electronic distributor? I really appreciate the help and suggestions I get on this site. I have been working countless hours getting this van back on the road. Cheers.

keep looking for evidence,,,,,,so when you unhook the linkage at the carb, step on the gas pedal, move the throttle plate to wide open, does the linkage show that it is actually putting the carb in to full speed?

If you're going to swap the ignition you'll also need to swap the the carb. You'll probably have to make or buy a carb adapter unless your head is 69 or later. A 78 Fairmont 3.3 DSII distributor is a direct replacement. With that distributor you can run anything from an msd box to fuel injection via a 7 or 8 pin hei module. But you're going to need a different carb to get away from the LoM ignition.

How was the tank's vent when you saw it? I could imagine a fuel delivery problem if the vent was plugged somehow. Maybe mud, maybe the tube is broken short or isn't tucked into the frame channel

I put a new vent hose on it when I had the tank treated. Seems ok. Im going to swap out coil this am, had to work yesterday. I also removed glass filter before carb and rerouted fuel line from tank to electric pump but got no love. I made an appointment at a local shop for tomorrow to check it out but Im hoping for coil today. Someone mentioned distributor loosing ground as it advances. Are the grounding points under the metal that holds the points?

Wow, I just figured out how to send a pic. That was a test. Just need to transfer phone pics to laptop and Ill show you guys what i have been working on.

This is my project van you guys have been helping me with. Replaced coil, checked fuel lines and removed fuel filter with no love. Going to the shop tomorrow. Ill keep ya posted.