High speed engine skip

[James G.]

Driving home at near 50mph engine would skip (not stall) but run great at idle and smooth at 35mph. Anyone heard of ignition point spring fatigue causing miss fire? Point contacts are still good with maybe 6000+ miles. Other option offered is coil failing, poor duty cycle. Fuel flow system checked out. Could point spring fatigue really cause high speed skip?

 

[modela@aol.com]

Original style points or the V8 points??

The speed shops sell higher performance V8 points that have better / stiffer spring action designed for racing...

 

[1crosscut]

Had the same type of troubles recently with a car I was getting back onto the road for a friend. I had freshly cleaned and re-built the carburetor just the week before. After looking all over the place for the cause of the high speed miss I ended up pulling the carburetor again and blew out all the jets and passages with compressed air. Did not see anything plugging anything anywhere. Put the carburetor back on and the problem went away. Wish I would have been able to spot what the trouble was but I guess I'll just have to be happy that it went away.

 

[C26Pinelake]

Driving home at near 50mph engine would skip (not stall) but run great at idle and smooth at 35mph. Anyone heard of ignition point spring fatigue causing miss fire? Point contacts are still good with maybe 6000+ miles. Other option offered is coil failing, poor duty cycle. Fuel flow system checked out. Could point spring fatigue really cause high speed skip?

What is poor duty cycle ? Wayne

 

[tbirdtbird]

"Could point spring fatigue really cause high speed skip?"

At 2200 RPM ????

Possible early head gasket failure letting in a bit of water which will short the plug and give a miss
Re-Torque

 

[Kurt in NJ]

I had a stock dist in the dist machine, it went into random firing at about 2000 engine rpm, above and below it was fine, all the parts looked ok,spring tension good, just a dab of dist cam lube and the problem went away,

another dist I had on the machine had a random problem in the 1500-2500 rpm range ,it had Ricks 'show quality script" points, that set had a loose rubbing block

NOS Ford points with a good cam didn't show bounce till the 4500+ engine rpm range

You would think why run the A dist on the machine because it has no automatic advance but the machine will show dwell changes when moving the plate and how well the cam and shaft were made----

 

[Mitch//pa]

My first thought is the lower plate wire having high resistance due to fraying etc.
As always diagnostics are in order so your not chasing your tail..
Drive it with a spark tester on it..and try richening it up by pulling the choke some ...

Had a few do that with the wireless plate set up... Pure junk

 

[BILL WILLIAMSON]

"Maybe" just a funky plug?? Or "maybe" the spark track to # 4, in the dist body, arcing out to the # 3 plug connector?? Look for a "fuzzy" spot on top of the body or check it in the DARK.
If you study the body on modelabasics.com you can see why it always happens at that spot.
Bill Skip

 

[larrys40]

To comment on your question yes, point spring tension can absolutely have an affect. I rebuild flathead V8 distributors and strobe them on my Ford Heyer stroboscope and test sets, and as Kurt said light spring tension can cause this kind of symptom.

The point spring tension should be around 18-22 ounces by spring tension. As Mitch said I would look for any possible connection issues as at the higher speed everything is taxed more. If there's someone who can test your coil for load test and output that would help. I like the early slogan of the Sun testers.. "We Test, not guess" ...

Check all primary and seconday connections...Keep us posted on your findings and process.
Larry Shepard

 

[Jon]

James, a quick and dirty trick to try. Put a glove on your left hand, with the engine running rev it up, stick your left hand over the carb. intake and pull it off just before it dies. Try this a couple times and then see if it runs better. Sometimes if there is something in the carb. you can clear it by doing this. Only takes a minute to try. I don't take credit from this, but a friend Steve showed me how to do this.

 

[James G.]

Driving home at near 50mph engine would skip (not stall) but run great at idle and smooth at 35mph. Anyone heard of ignition point spring fatigue causing miss fire? Point contacts are still good with maybe 6000+ miles. Other option offered is coil failing, poor duty cycle. Fuel flow system checked out. Could point spring fatigue really cause high speed skip?

Thanks all for your encouragement and ideas. Test not guess!!! I'm headed to the garage to check the plate lead and change the points. I also have a new spare coil as backup on the road if needed be. Another sayng goes "righty-tighty"!!

Jim G.