Engine rough

B

bonanza7369

Member
Have a 56 Ford with 292
Engine is rough with kind of a stumble when reving it up smoothes out when Rpm is higher
Idles ok and doesn't smoke.
Just had the plugs out and cleaned them.wires and dist. cap are new.
Any ideas
 
A few things to check in addition to carburation...
Valve adjustment
Compression test
Vacuum test
Points/dwell and timing, confirm vacuum canister advance function


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The engine would not idle good or run good when the RPM is raised if it had crossed plug wires.
If you do what DMSFRR said and nothing found, then you may have an issue with the carburetor.


Sal
 
scicala said:
The engine would not idle good or run good when the RPM is raised if it had crossed plug wires.
If you do what DMSFRR said and nothing found, then you may have an issue with the carburetor.


Sal
Click to expand...

Will check out some of the things. Carb was overhauled about 2 yrs ago
wires are correct. Thanks for reply
 
If it will rev up smoothly with gradual gas pedal, but bogs if you push the pedal fast check your accelerator pump.


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@runmikeyrun - I have this problem actually but I'm a newbie. Whats an accelerator pump? do you mean fuel pump ? where is the accel pump located?
 
delco1946 said:
@runmikeyrun - I have this problem actually but I'm a newbie. Whats an accelerator pump? do you mean fuel pump ? where is the accel pump located?
Click to expand...



First I will ask what kind of carb you have. Use google to find out where the accelerator pump linkage and nozzle are.

Accelerator pump will squirt a little jet of fuel into the carb when accelerating, the faster you hit the pedal the more fuel it will squirt. It’s to compensate for the sudden addition of air.

On a Holley 4150/4160 it is activated by the throttle linkage and a lever that pushes on a diaphragm inside the float bowl. The nozzle is up on the top of the carb. At times the passages become plugged with crud, which can come from shellac/junk inside the float bowl or deteriorating float bowl gasket material (my case). In some cases the diaphragm will tear or the linkage will bind.

With the engine off you can look down the carb barrel and open the throttle. You should see a jet of fuel squirt out from the pump nozzle. If not, you’ll want to investigate. Since the car is not running don’t squirt a bunch of fuel down there or you could flood it, just a quick squirt will tell you if it’s working or not.

I usually err on the side of caution with the engine off because no one wants a backfire in their face looking into the carb with the engine running!

While it’s possible this could coincidentally happen after you changed the wires/cap it’s less likely. Depends on how long your car was sitting. My truck had this problem after sitting for a couple months while I sorted out some issues. Kinda caught me off guard because it was working fine when the truck last ran.

I would retrace your steps with the wires/cap if the accelerator pump is working ok. It’s possible the timing is a little off or a terminal isn’t getting spark from the rotor if the cap isn’t seated properly. Could have knocked a vacuum line off but you’d also notice a high idle.

Sometimes it’s weird stuff too. I ordered a new cap and after removing it a couple months later I noticed it was just a hair short; the rotor was shaving off pieces of the copper contacts as it went around. Got a cap from NAPA and it is the right height and the truck runs a little smoother.



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Have you considered a defective new plug or wire?

After idling for a while to get the engine up to operating temp, compare the colour of the plugs. It tells you alot of what's happening in the combustion chamber.

They should all be similar ... fluffy grey/beige.

A wet or dark one is the problem cylinder
 
If you 292 has the stock carburetor, it may have a leather accelerator pump. If so,remove the pump and work your fingers around it with some 30 wt engine oil to rejuvenate the leather. This can be done every spring until it no longer works.
 
The accelerator pump is inside the carburetor. On a '56 Ford, if it is the factory 2bbl, that is a Holley 2110. It was only used that one year. The accelerator pump is located in a vertical bore on the passenger side of the carb. Take the top air-horn off and you will see a long stem with a disc down at the bottom that has a rubber or leather cup affixed to it. If the accelerator pump goes bad, you will not get a good blast of gas to the venturi's when pushing the gas pedal down.
Some cars had a Holley "Teapot" 4-bbl carb. I don't know where it is in there, but there are lengthy re4build instructions for both carbs in the '56 Ford car shop manual.
 
If one plug seems to be mis-firing, or not firing at all, it is easy to determine which one by using a timing light. Just wrap the probe of the timing light around the plug wire (as close to the plug boot as possible) and press the trigger and watch the light bulb. If it is flashing consistently, you are good on that plug. Check the next and repeat until all eight have been checked.
Any plugs that are not firing might be corrected by shutting off engine and checking connections of plug wires at the distributor towers. Pull the boots up high on the plug wires at the distr. towers. Grab the plug wire and push down hard till you hear a click. Slide the boot back down over the tower.
 
What is the initial advance set at? YBlocks seem to run better at about 10-12 degrees instead of the 6 or so in the book.
 
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