New distributor skips a beat

[stewgee]

I have installed a new distributor complete with all new insides ie points, condensor etc. Have timed the engine a minimum of 3 times but the engine still has a hiccup (sputter) every few revolutions. The new original style distributor cap feels a little loose and doesn't fit as snug as the modern style cap that was on the old distributor. Anyone have any ideas what might be causing the frequent sputter?

[katy]

Possibly the new condensor is not so good?
How about the spring contact on top of the rotor? Is it sticking up enough and springy enough?

[old31]

Have you checked the gap between the rotor tip and the 4 posts inside the cap?

[30 Closed Cab PU]

If you have the old distributor and its components are OK, possibly try swapping in old parts into the new distributor. Try cleaning all ignition connections, make sure you did not screw the large cable in too far on the distributor, clean the points contacts. Check/clean/gap the spark plugs. Check each plug for a nice good spark.


Why did you replace it? Was the old one showing this or other symptoms?

[rocket1]

I agree with 30 closed cab pu,if you did not have the problem before it is the new dist. thats causing the problem or something that you did or not do.

[Jim/GA]

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Ha ha ha!


Now that I got that off my chest...

It may not be ignition. It may be fuel mixture. Or a sticky valve. Check GAV and idle mixture.

Check that the breaker plate has a good connection to ground inside the cast iron distributor body. New distributor means fresh paint. If the groove inside the cast iron body has thick paint in it, the points don't get the ground they need. Same with the spot where the condenser attaches (if using original style condenser).

Make sure the points are still gapped at 0.020" and put a small dab of cam grease on the cam. That new cam follower will wear down quickly at first and you need to regap the points to correct for it.

Confirm the coil is wired with correct polarity.

I, too, suspect the new condenser. Try swapping in another new one to see if it makes any difference.

Be systematic and change only 1 thing at a time. Let us know what you find.

[Jacksonlll]

Take a close look at the movable point arm. Sometimes the arm can short out on the cam.

[stewgee]

Update. Checked out some of the suggestions that you guys talked about but the engine still "sputters" a bit every so often. Re timed and double checked the point gap. She fires up just fine with the spark lever up and sounds good. Pull the lever down a couple of notches and she levels off and then will kinda skip a beat seems like every 10-15 revolutions. Give it little gas and I get some mild backfiring. (this usually indicates a timing issue) Question. When you tighten the point cam down after timing the engine is the cam supposed to move back and forth a little? I've watched some videos on timing and it appears that when the point cam screw is tightened they don't use the cam wrench. On mine when I tighten the cam screw I have to hold the cam in place with the wrench but it still moves a little after tightening the screw. Is this normal?

[1931 flamingo]

It will move some CCW, normal, Try putting some Marvel Mystery Oil or ATF in the gas and run it. For you probably 6 ozs. Won't hurt anything.
Paul in CT

[30 Closed Cab PU]

Originally Posted by stewgee

Update. Checked out some of the suggestions that you guys talked about but the engine still "sputters" a bit every so often. Re timed and double checked the point gap. She fires up just fine with the spark lever up and sounds good. Pull the lever down a couple of notches and she levels off and then will kinda skip a beat seems like every 10-15 revolutions. Give it little gas and I get some mild backfiring. (this usually indicates a timing issue) Question. When you tighten the point cam down after timing the engine is the cam supposed to move back and forth a little? I've watched some videos on timing and it appears that when the point cam screw is tightened they don't use the cam wrench. On mine when I tighten the cam screw I have to hold the cam in place with the wrench but it still moves a little after tightening the screw. Is this normal?

Should not backfire - this and the skip a beat can also be caused by running too lean. GAV Not set correctly, idle mixture not set properly, carb issue, leaky intake manifold, leaky carb to intake manifold gasket, clogged fuel filters starving the carb. Still could be ignition issue though.


1st easiest thing to try is try different GAV settings and see if idle and back firing symptoms diminish/go away. Then Check the plugs to see condition.

[katy]

Originally Posted by 1931 flamingo

It will move some CCW, normal, Try putting some Marvel Mystery Oil or ATF in the gas and run it. For you probably 6 ozs. Won't hurt anything.
Paul in CT

Yep, it does sound like you may have a sticking valve.

[100IH]

And if not GAV, monkey with the Air bypass screw: changes the mixture at slow idle. Actually the GAV shouldn't affect the idle but in reality it often does, but that point is a fine point. So, the screw you are looking for is on the upper body, knurled head with a spring. In is richer, out is leaner - adds more air to the idle fuel. Also, is the new distributor body a reproduction or original? How is the side to side play on the shaft where the bushings hold it in alignment.? Might try to smell the exhaust. Rich will tend to bun your eyes and lean not so much.

[Purdy Swoft]

Originally Posted by katy

Yep, it does sound like you may have a sticking valve.

I agree and adding MMO would be my first try .

[stewgee]

Going to try the MMO for sure. Have adjusted the air intake jet to the one and a half turns out. Other than that I don't see any other adjustment on the carb except the throttle adjustment.

[Railcarmover]

when you think its fuel, its electrical,when you think its electrical, its fuel.when its 'skipping short out the plugs on at a time...if that doesn't do anything most likely its fuel...stuck valve...might want to check the timing gear as well

[1930 coupe]

I have seen occasional stray arcs inside the distributor cause a miss when it arcs. You can check it by taking a old or spare cap and cut the sides off it with a dremmel tool and a cutoff wheel, so you can see inside the distributor with it running. Install the cutoff cap and run the engine in a dark place or at night and watch for stray arcs inside or outside of the distributor. Your engine usually will miss at the same time that you get a stray arc in the distributor. The picture shows a cut off cap. After testing remove the cutoff cap and put the uncut cap back on.

[Flathead]

One thing that might help narrow down the problem is using a spark tester like the Nurex one. It has an adjustable gap and you can watch the spark while the engine is running. When the engine stumbles see if the spark skips at the same time if it does you will at least know it is the ignition, if the spark is steady and good the problem is likely elsewhere. I'm not pushing Nurex, any similar tester will work, I just happen to have a Nurex.

[Smooth_One]

Originally Posted by 1931 flamingo

It will move some CCW, normal, Try putting some Marvel Mystery Oil or ATF in the gas and run it. For you probably 6 ozs. Won't hurt anything.
Paul in CT

I run Marvel Mystery Oil through every tank!! Run it in all my modern vehicles as well! Oil and gas.

[stewgee]

Originally Posted by 1930 coupe

I have seen occasional stray arcs inside the distributor cause a miss when it arcs. You can check it by taking a old or spare cap and cut the sides off it with a dremmel tool and a cutoff wheel, so you can see inside the distributor with it running. Install the cutoff cap and run the engine in a dark place or at night and watch for stray arcs inside or outside of the distributor. Your engine usually will miss at the same time that you get a stray arc in the distributor. The picture shows a cut off cap. After testing remove the cutoff cap and put the uncut cap back on.

Now that's interesting. May have to try it.

[1930 coupe]

Originally Posted by stewgee

Now that's interesting. May have to try it.

I have seen the arc go down to the points, happens more often when using extra high voltage coils.