backfiring and missing on acceleration

[flattiefreak]

i have made quite a bit of progress on the 58 plymouth 230 flattie in the past few weeks. it runs smoothly at idle and in neutral when i accelerate.

but when im in gear and im giving it gas and letting off the clutch it misses, backfires and stalls. it does this only sometimes. most of the time it will just backfire and bogg down quite a bit. then return to normal smooth idle. i dont know if this is a problem with ignition timing or aasomething with the clutch.( 3 speed on the column) have any of you had this problem? What is causing this?

[Plymouthy Adams]

check your condenser

[Don Coatney]

Is the accelerator pump in your carburetor working correctly? With the engine turned off and the air cleaner removed you shoulod be able to look down the throat of your carburetor and see a healthy squirt of gasolene when you move the throttle from the closed position to the fully open position. If you do not see this your accelerator pump is not working correctly.

['37 P4 Touring]

i have made quite a bit of progress on the 58 plymouth 230 flattie in the past few weeks. it runs smoothly at idle and in neutral when i accelerate.

but when im in gear and im giving it gas and letting off the clutch it misses, backfires and stalls. it does this only sometimes. most of the time it will just backfire and bogg down quite a bit. then return to normal smooth idle. i dont know if this is a problem with ignition timing or aasomething with the clutch.( 3 speed on the column) have any of you had this problem? What is causing this?

Need more information to help you. For instance, has it been sitting up for years, has it just been overhauled, how old is the fuel, what have you checked so far?

[Don Coatney]

Need more information to help you. For instance' date=' has it been sitting up for years, has it just been overhauled, how old is the fuel, what have you checked so far?[/quote']

What does overhauled mean? Something to do with Mrs Murphys chowder?

[Tom Skinner]

Is it backfiring out the Tailpipe or the Carburator?

Backfiring:

(1) As a general rule, backfiring into the muffler indicates too rich a fuel mixture and backfiring into the carburator, too lean a mixture. Make the nec-

essary adjustments at the carburator. Automotive Trouble Shooting For WW2

Wheeled Vehicles, Volumne 1 by Robert V. Notman. Pages 9 &10.

Use a Vacumm Gauge to set the mixture:

1. Warm up motor.

2. Hook up Vacumm Gauge at the Intake Manifold.

3. Set the mixture screw to obtain the highest reading in inches.

4. Turn the screw clockwise to lean, counterclockwise to enrich.

This usually is between 19-21" A steady Hand indicates a healthy engine.

Other things such as misfiring under a load indicate a weak secondary current

in the ignition circuit, Check Plug Gap, Point Gap, Distributor Cap, and all Wire Connections. Page 9.

Extremely late Ignition Timing will cause backfiring. Check Timing. Page 10.

Tom Skinner

[flattiefreak]

thanks for the replies. the engine has just been rebuilt last summer. car hasnt been driven too much. since the rebuild. my acc. pump is working correctly. all plugs were recently changed and gapped to service munual spec. The plug wires are a bit old, as well as the cap and condensor. i will be getting a vacuum gauge this weekend and set mixture screw and maybe adjust the timing a little bit. sounds like its popping through the carb. i will replace the plug wires, dist. cap and condensor very soon and see if its improves. any tips for replacing the condensor?

[Plymouthy Adams]

IF you tuned the car up and went with just new points and not change the condenser therein may lie you entire problem..the condenser will decay as the point get wear and increase in resistance resulting in diminished capacity...also...I sure wish I had a dollar for every NEW condenser that has filed out of the box or within a few days of tune..always change the condenser with the points...a failed condenser will give you excellent idle, rev to no end..but as soon as that sucker gets in gear..it falls on its face and if you do get past the hucking and bucking and other maladys..top speed may be 25 mph...pop your cap and inspect the points for a blueish hue that indicates excessive current or if you have been running this long trying to troubleshoot may have transistioned to a blacker burnt condition..

[Tom Skinner]

Condenser Tests:

To test the Condenser without removing it from the distributor, crank the engine until the fiber rubbing block of the points is midway between two lobes of the cam. Turn the vehicle ignition switch on and snap the contact points open and closed by hand: at the same time observe the point contacts for evidence of flash. No arcing across the points indicate a bad condenser, a slight flash indicates a normal condenser. Page 28.

Tom

[flattiefreak]

from what i could see the points doesnt look blueish or burnt. when i replace the points and condensor should i take the dissy out of the car?

[Tom Skinner]

You do not need to remove the Distributor to change the points or condenser

Tom

[greg g]

Points changing, and general serivcing of the distributor is much easier done on the bench. while it can certainly be done in the car, working at the strange angle in the space between the engine and inner fender can sometimes make it harder than it needs to be.

Removing it is easy, disconnect the coil wire, dissattach the lie for vacuum advance, remove as move the cap aside, mark the location of the vacuum advace in relation to the block, and the rotor to the distributo body. the remove the hold down clamp bolt, and pull the distributor. When reinstaling it just put it back assuring the rotor and body are indexed to the marks you made.

[John Reddie]

Also check the small pigtail wire the connects to the points from the ignition wire terminal on the distributor. This small wire can sometimes make contact with the side of the distributor when the engine speed is increased due to moving breaker plate and eventually wear through the insullation. It will idle ok but short out when the speed is increased. It can drive you crazy. Good luck to you.

John R

[Tom Skinner]

Good Idea John Reddie.

Tom

[flattiefreak]

i gapped the points and replaced the condensor with the dissy out of the car. i did forget to note which way the rotor was pointing. any way to find out which way its supposed to be pointing?

[daddyo23]

You have a 50/50 chance of being right. The tang on the end of the dizzy will only go in one way,right, or the other, which is 180 off.

[Don Coatney]

i gapped the points and replaced the condensor with the dissy out of the car. i did forget to note which way the rotor was pointing. any way to find out which way its supposed to be pointing?

If it is 180 degrees out the engine will not run.

[flattiefreak]

i just put the dissy back in and also installed a new set of plug wires. and tried to start it. it just spun over and over. so i flipped the rotor 180 degrees around and tried to start it. thios time it sounded like it was wanting to fire. i kept hearing a popping noise through the carb. i installed the dissy as close to the same position as i had it before. would it act like this if i am one plug wire off? i have them in the correct order, i just might be one off.

[greg g]

unless and until you have found TDC for cylinder #1 , ad alligned the rotor and plug wires properly to relfect it, any firther action and or discussion is futile.

[flattiefreak]

i got her running again today. she runs smoother since i installed the new plug wires and condensor. but, now every time i step on the pedal i get one loud pop from the carb. my question is, when you change the point gap should i adjust the lean rich screw on the carb? someone mentioned earlier on this post backfiring through the carb means to lean a fuel mixture. it seems no matter how far i rotate the dissy, it still backfires in the carb.

[Plymouthy Adams]

did you properly set the timing..this is pretty much critcal on the flat head..improper timing can cause this and will also lead to high engine temps..

[flattiefreak]

well, before i time my engine with a timing light, i like to get it running smoothly with no popping or backfiring on acceleration. then, i time it.

[Young Ed]

Thats backwards. Timing it gets it running smoothly.

[greg g]

Turning the screw on the carburetor only effects the idle mixture. It has no bearing what so ever on how the engine runs at any speed above idle. The running mixture is set by the jets in the carb and is non adjustable without changing the jets themselves.

threre are three things which can contribute to a lean mixture at running speed. Blocked jets, restricted air flow into the carb, or an air leak between the carb and the block. Some will mention a restricted exhaust but this works essentially to limit the air flow through the carb.

Again the first critical adjustment is establishing proper timing. If the spark is not getting to the plug at the proper momet all other adjustments are without merit.

[Don Coatney]

It still sounds to me like your accelerator pump is not working and your timing is "off".