Misfiring because of worn timing chain?

[Jeff Balazs]

I'm in holyday so I don't have the paperwork with me :-(.

The engine runs better with the pointless ignition but it just shifts the misfiring from 30-40 to 40-50 miles. That's why I thought it might be something else. One idea is, that the main metering jet in the carburator is too small. But I installed the original rebuilding kit so it might be right. Maybe it has something to do, that it's a 1950 engine with the original carburator and ignition. Think the swapped the engine sometimes and installed the original stuff. As far es I know it shouldn't make any differences but who knows.

Interesting that the MPH of the misfire changed when you swapped in pointless ignition. Have you done a static timing verification?

Have you checked to see if each plug wire is good? Just because something is new doesn't mean it is actually good. I have had problems with some new plugs and wires in the past. What plugs and gap setting are you using?

 

Jeff

[Kai-by-Vecona]

Yes, I installed a new ignition coil. Plugs are NGK I guess and also the wires. I double ckecked these and also tried other spark plugs. I never tried a static timing. I don't know if it works with pointless ignition. May it be possible that the output of my generator is too low? Just a guess because when I run the car, the gauge does not show very much charging....

[Don Coatney]

What replacement coil did you use? Is it possibly an internally resisted coil? Check the voltage at the coil primary wires on the distributor side and the power side and report the readings. Also check your battery voltage at idle and at 1500 or so RPM's.

[Jeff Balazs]

I am usually a big fan of NGK plugs.......but when I tried them in my flathead they did not seem to perform as well as the Autolites. Harder starts when cold for certain.

I asked about the gap for 2 reasons......it is different for resistor and non resistor plugs.......and if you have a high output coil it may need to be opened up a bit. You will need to check your paperwork. I have the Pertronix point less set up in my truck. I like it but some have had problems. I don't think there is any thing wrong with what you have put into yours as usually they either work fine or not at all.

 

I suppose you could be getting some form of fuel starvation. Have you done any sort of test on the output of the fuel pump?

 

Again I hope this is helpful. Jeff

[soth122003]

While I am not sure this is your problem, I would check the generator. Mine had bad brushes and one of the brushes was not even making contact. When I started and idled the car everything seemed fine, but at higher rpm and speed it would miss and spit. The battery could not keep up with the demand of the electrical system at speed especially when the battery was not being charged and was low. The most I could get out of the car was about 45 mph. After the genny rebuild, I have had it up to 80 mph on a test drive.

 

I also have a pertonix ignition module on my P-15 and it works very well.

 

Joe

Edited December 29, 2014 by soth122003

[Kai-by-Vecona]

Thanks a lot everybody for all the good ideas, seems I have some homework to do now.

 

I unistalled the radiator because it's leaking and I'm going to fix it so this is the possibility to do the timing chain job but as I could see, there are a lot of more things I should check. Only problem is, for most of these checks I had to run the engine, what is not possible now. Maybe I have a look at the chain how it looks and when it seems to be ok I will try all the other ideas and let you know.

 

Thanks a lot. I'll let you know what works best

[Dodgeb4ya]

The timing chain is easy to check.

[suntennis]

You mentioned rebuilding the carburetor which should include checking the float adjustment. If the float adjustment is off it could cause the engine to lean and limit maximum speed as well as poor acceleration.

[Kai-by-Vecona]

@Dodgeb4ya. That's what I mean. I just will have a look. I think it should be easy to see if the chain or sprocket is worn.

@suntennis. I tried to adjust it but maybe it's worth a second look

 

Thanks

[Plymouthy Adams]

you can tell approximately how much slop is in the chain by looking at the rotor and degree wheel and rotate the engine backwards till the rotor moves and read the degrees...

[RobertKB]

If you remove the bolts from the timing chain cover keep track of which ones go where. Some go into the water jacket and will leak if not properly sealed. I think they originally came with a lead or copper washer when new. Use a sealant when reinstalling.

[Dodgeb4ya]

Don't need to pull the cover.... just do as Mr. Adams says to do.

[Kai-by-Vecona]

Thanks for the tip!

[Kai-by-Vecona]

@soth122003: Uninstalled the generator today and everything looks fine. Also brushes have good contact and they look quite good. Seems to be something else.

@Plymouth Adams. Is there are maximum of degrees that is normal for the slop?

 

Thanks for the tip and a happy new year

 

Kai

[Plymouthy Adams]

you will need a degree wheel or if not a degree wheel at least do the test with the timing indicator and the degrees marked on the damper/pulley...varying degrees of slop is to be expected...form new at 3-5 degrees to well 15 + of slop for one in advanced wear..when slop gets to about 20 degrees or so it can often cause a lowering of the compression as noticed when doing a compression test...though it is hard to actually account for this as normal ring wear will do the same..that is why the slack test can be of importance...

Edited January 2, 2015 by Plymouthy Adams

[Dodgeb4ya]

Just turn the crankshaft pulley back and forth an inch or two by tensioning the fan belt with your thumb then rotating the fan back and forth and and see how much the crank pulley moves in comparison as to when the rotor starts to move. A worn chain will have an inch or more crank pully movement of rotation before the rotor starts to move.

Excess chain slop.

[Plymouthy Adams]

you can use a strip of masking tape around the pulley..mark the extremes of the movement on the tape...now remove and measure the tape length...1 divided by the tape length times 360 will give you the exact amount of degrees of slack

[Kai-by-Vecona]

So... long time until last post but I was busy and didn't find the time to look at the car.

 

I made the test of the chain slop and it shows about 25-30° until the rotor starts turning or about more than 1 inch of the crank pulley movement. Look like I should have a better look at the chain.

Does anyone know the size of the tool for the crank pulley nut? Ist it 1" 5/8?

 

Kai

[DonaldSmith]

The crank pulley nut on my 47 DeSoto is 1-13/16.

 

[casper50]

The one on my 47 Dodge is also 1 13/16.  I just had to buy a socket for it.

[greg g]

There are 2 or 3 different sizes,

I think mine was 1 11/16, just buy all three and return the wrong ones.

[Dodgeb4ya]

Take your pick...

[casper50]

If SAE are hard to come by metric will work.  When they get that big there's not much slop difference in 1 13/16 and 40mm

[Andydodge]

Before you completely remove the front pulley check that the movement you noticed is not just the pulley loose on the crankshaft flange..............they are riveted together and can become loose or show some wear........there are a few different style flanges/pulleys and outside of the USA it can be hard to get an exact replacement........I ended up tack welding my original flange/pulley together at 4 opposite places and it solved the problem for the time being........but as a couple of guys have mentioned if you do have to remove the timing cover make SURE to note exactly which bolt came from where and use a good quality thread sealer when you reinstall them.........andyd

[Plymouthy Adams]

if the man is turning the crank via the nut as he should there is no slop but that of the chain and what little gear lash is on cam/oil pump drive...and possible a tad in the distributor plate..