Lets try again-21 stud motor runs like crap

[bullrunmotor]

Motor ran great for 10 years with dual 97 carbs, eddie meyer manifold and std ignition.. Started running bad-missing--no power. I have good compression. I have done the following-tried several known good distributor set ups off my other flatheads. Put 2 recently rebuilt haney coils on unit. Distributors have been set up on strobe/machine,the same distributors run fine on my other cars. Tried new ih200 and napa 49 condensors. Wires and plugs are almost new. The ignition will throw a bright blue spark damn near an inch. Have tried 4 different 97 carbs which i've rebuilt with new power valves. Swapped out a different 2 pot manifold.
Pulled heads-found several tight clearances on valves. Pulled all valves springs and keepers. Checked all. Lapped valves. Rebuilt my mechanial fuel pump. New ignition resistor with 3.8 v reading at coil. After last manifold/carb swap the motor runs with black smoke-more out of the right side dual exhaust than the left. I have an old single manifold carb set up i'll try next. I've read guys plugging up heat riser tubes fixing problems or possibly heat riser passages in manifold could be bad. I'm going to revisit with a vacuum gauge and see if it tells me anything new. Any suggestions appreciated. Truck ran great for 10 years-it will be interesting to see what it is.

[D. Jones]

Sounds to me like a fuel problem, I.E starving.

Do you have any rubber gas line in the system? If so you might want to check to see if it has either a air leak, (sucking air) or if the inside has collapsed or dropped a flap of material that is restricting the fuel flow.

I would put a fuel pressure gauge on it and if the pressure is OK I'd pull the line to the carbs and check the flow.

Just my $0.02 for what it is worth.

[bullrunmotor]

I've GOT SOOTY PLUGS-BLACK SMOKE. FUEL PUMP WILL FILL A CUP IN SEVERAL MOMENTS OF CRANKING. FUEL LINE IS GOOD.

[Jack E/NJ]

>>>plugs are almost new>>>


Not any more. Gotta get that soot & carbon off the center insulator. Even after cleaning them, enough can remain for the spark to jump to ground up inside the plug instead of at the tip. This quickly causes even more soot buildup. Either try new plugs or burn the carbon off by running the plug off an AC oil burner coil and blowing air at the spark till it only jumps at the tip. Jack E/NJ

[Mart]

If you have another vehicle that has the same distributor, carb and coil, you could make sure the other vehicle runs right and then swap all 3 items as a set onto the problem vehicle.

Or put your items from the problem vehicle onto the known good vehicle and test them. One by one may be ok to do. Swap one item, does the good vehicle run like crap? yes - that's the problem item. No? Swap back and then swap the next item.

If all three items get swapped with no ill effect on the other vehicle you then look at things like fuel supply, ignition wiring, ballast resistors etc.

Make sure you also swap the ignition leads and rotor, and maybe the plugs should be brought into the mix.

An hour or so of switcheroos should get some sort of indicator as to where the problem lies.

Mart.

[drolston]

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A long shot, but: For a total freaking mystery, I always think to check the ground path. Disconnect the battery lead on your coil. Put a sensitive ohmmeter (one with a 1 ohm scale) between the distributor side of the coil and the ground terminal on your battery. Turn the engine slowly through both sets of points closing and opening. If you see even half an ohm with either or both points closed, that could cause ignition problems and missing. If you find excessive electrical resistance, work your way from the coil terminal to the engine and chassis ground to find where the resistance is. Touch where the coil wire connects to the distributor. Then where the lead connects to the moving points, then to the fixed part of the points, then to the breaker plate, then to the distributor housing, then to the engine block, etc.

[Tinker]

I usually run a ground from the frame ground to a engine headbolt. Not stock as the ground is to the cowl only, but it helps.

I like a ground on all 3 areas from the battery (frame,body,engine) overkill I'm sure.





.

[Tinker]

Try a knew condenser maybe.

[Brian]

I had the same problem...took me months to sort...like you I thought it could be the heat riser blown out, but didn't want to believe it; I was so sure it was ignition related. Finally, removed intake, plugged risers, and twas a beautiful thing....

[Tinker]

Heat risers for all practical modern reasons are pretty much useless. Maybe if you need to get to work and it's 20f or less degrees out. In my opinion anyway.


as Mart said. one thing at a time. Hard to track otherwise.

[flatjack9]

And I pretty much think you are wrong.

[Tinker]

Flatjack if too me. Explain?

[Terry,OH]

Is the engine vacuum steady at idle? With duals may be around 15". Sounds like it is RICH Do check fuel pump pressure 2-2.5# Also carb float level.

[Charlie ny]

The test motor in my shop takes a beating and when it begins to miss behave I have
learned that it is demanding NEW plugs. I use AUTOLITE 847's one heat range hotter
than the Autolite 216's I use in my '41 p'up. I will mention cleaning sooty plugs will
sometimes buy me a day or two.
Charlie ny

[deuce_roadster]

I don't think 3.8 volts at the coil is enough. There is a threshold at which the coil works properly and I think it is over 4. I think you are losing voltage at the switch or somewhere between the battery and the coil.
Try jumping a hot wire from the battery directly to the coil and see if it runs better.

[Jack E/NJ]

bullrunmotor>>>The ignition will throw a bright blue spark damn near an inch.>>>

Maybe you burned the coil out doing this. 8^0



Jack E/NJ

[Dave Castle]

Love it, one problem, 50 solutions !!!

[rotorwrench]

I'm not sue what year of engine we have here. Those early ones can have manifold internal problems as mentioned. They will run lean though. Black smoke indicates rich but on one side only a person has to look for an internal fuel leak affecting that side. Choking down the air intake on a lean running engine might make it run better. Not as easy on a dual carb set up. On a rich runner, it would likely kill the engine. A sticky valve can do some weird stuff if it's intermittent. Aren't these old engines fun!

[Flathead Fever]

It sounds like you tried replacing everything with good known working parts. That eliminates a lot of the possibilities. Pulling the heads was a little drastic. That is what the vacuum gauge is for. It will tell you if you have a valve problem. It sounds like you checked out the valves pretty well. I would still put a vacuum gauge on it. You could still have a valve sticking while its running but not when your turning it over by hand. A compression test does not always tell you the whole story.

Does it run bad both at an idle and driving down the road? Does it get worse with more throttle? Does it change when the engine is cold compared to at operating temperature? Is there anytime it does not run bad?

Is this still a 6V system or 12V. If the coil has been rewound for 12V, 3.8V might be too low? You need to find out what the operating voltage of your coil is suppose to be.

When you had the heads off did you look to see if all the cam lobes are opening the valves all the way?

Is the fuel new? This new fuel is only suppose to be good for about six-months before it does not burn correctly

While its in the driveway you can try spraying some carb cleaner, starting fluid or propane in the engine at different rpms to see what difference it makes?

Did this problem start while driving or after the vehicle sat for awhile?

Fuel flow and fuel pressure are two different things. Each pump will have a pressure rating and a flow rating, so much fuel in so many seconds. You should check both pressure and volume.

Does the engine have a timing mark you can check? This is why it is so important to make a timing pointer on the pre-8BA engines. When you had the heads off would have been the perfect time. That way you would not need somebody to strobe your distributors anymore, you could set the timing yourself and it would be more accurate. Plus you could make additional timing marks for checking the total advance.

The heat riser passages have nothing to do with your problem. Some of the flathead racing intakes don't even have them at all. Lots of guys plug them up because it also changes the sound of the exhaust. It gives it a nice deep sound. The heat crossover passage is there to help the fuel turn to vapor when the engine is cold. The gas has no problem doing this once engine is at operating temperature.

When I foul out plugs really bad, like on my lawnmower. Letting the plug dry doesn't seem to work. Taking a match to it and trying to burn it off does not work. I usually end up bead-blasting them. What I don't like about that is the beads can get stuck down inside the plugs where they will be able to fall out into the cylinder. I blow them out real good with 120 lbs of air and then look down in there with a bright light.

This is probably not the problem since it sounds like you have a rich mixture but I'll throw it out there since you have replaced everything but the block. Try giving it an alternative fuel tank and hose directly to the fuel pump (not in the garage so you don't burn it to the ground).

I had a neighbor that bought a church van for his family to go camping out in the desert. It ran fine until on the way back. On the way back it quit running. It took me a whole day to figure it out. If you let the vehicle sit for when I checked it I would have good fuel flow out of the mechanical fuel pump. I'd start it up and I could drive it again for about 20-minutes before it started sputtering and died. I'd let it sit for awhile and I could drive it again. That would usually be an ignition problem or even a vapor lock condition on a hot day.

I finally removed the engine cover (its a van)and hooked a clear piece of fuel line up at the carb. With the engine cover off I could watch that clear fuel line while driving down the road. It took twenty miles but the fuel finally stopped flowing and we coasted to the side.

While out in the desert riding three-wheelers in the sand dunes his three-year-old son poured sand down the van's gas tank filler, probably a couple of cup fulls. After it had been driven awhile the sand would get sucked up against the fuel strainer in the tank and the engine would run out of gas. If you let it sit awhile the vacuum from the fuel pump dissipated and the sand would fall back off the strainer and the van would drive again for awhile. Maybe you have a bunch of rust in the tank doing the same thing? Like I said, this is probably not since it seems to be running rich.

I bought a used tractor that did the same thing. It turned out somebody had dropped a piece of plastic down in the tank. Eventually it would get sucked up against the fuel line and the engine quit. I'd pull the line off the carb and blow air back into the tank and it would run again. It might run a week or five-minutes.

I thought of something else. At least a dozen times in my career I had alternators leak AC voltage into the electrical system through a shorted diode. This caused the engine to misfire and barely run. This was on carbureted vehicles with electronic ignitions. The alternator would appear to be charging correctly and you would never guess there was a problem with it but if you unplugged the wires from the alternator the engine straightened right out. What I do not know is if the AC voltage was messing with the ignition module or the coil? It sure made them run terrible. I also don't know if it would have any effect on a points type ignition system?

[bullrunmotor]

Cant adjust valves by grinding the stem without removing heads