ok guys I’m new on this I hope I can get some help. 68 valiant got the 318 la. Holley 650 performer dual plane intake accel coil and plug wires. Fuel pressure regulator set @6 new cap and rotor. Distributor is stock. Cam and heads stock. So I have a very strange issue. Car misfires bad and I’ve been chasing this issue for a while. New balace new cap and rotor plugs wires re sealed all vacuum lines and gaskets on the top end. No leaks I can find. Going crazy trying to find the solution. Finally after messing with it enough I realized that if I lift up on the back of the distributor cap a bit or like push it forward. All the misfires stop. Idle picks up. It’s fine. The distributor does have some shaft play in it but nothing major that I could see cause an issue but idk. Maybe 1/16 or a little more. Any suggestions.
Distributor cap issue
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Mechanical advance stuck?
rustycowll69
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are cap and rotor same manufacturer? Are they the correct cap and rotor for your type of distributor(points or electronic). Perhaps the center contact of rotor is bent, not contacting center contact of cap cleanly. Look for cracks or carbon tracks in cap.
See that’s what I thought too rotor sees to be making enough contact but I pushed it up a little and put a small rubber seal under the rotor to push it up slightly to see if it would help. With no luck. I can feel it hit the contact and it’s only missing on cyl 1 and 7 it seems. At first. But it’s gotten worse. Advancing the timing seems to help a bit but still misfiring
I have two good caps for the car tried both no success. I’ll try and see if I can get a new rotor tomorrow. Hell for 3 bucks. Why not but it’s just strange. I have it set around like 10* initial. Just trying to get it to idle. Pull up on the cap a bit or push it forward. Idles up misfires disappear I’m convinced the cars possesed. It is a points distributor. Points in decent shape
Yup. The gap will vary.next to no play in shaft is ideal, and if it moves as much as you described in an earlier post, you might want to contact @halifaxhops and see if he has, or is willing to overhaul yours.
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Also, if lobes in dist are worn,it could cause problems too.
How about turning distributor,so wires line up to next tower, then move wires and see if misfire moves?
How about turning distributor,so wires line up to next tower, then move wires and see if misfire moves?
CCHHAARRGGER!
Well-Known Member
Time for a new distributor. I discovered Oriely offers new distributors not reman for about 100. Assuming you have electronic ignition then the distributor is the cause. You said the distributor is stock which I think is french for old. One time I had the the air gap between the reluctor and the magnetic pick up completely close off and it caused the same issue you are describing . It was a reman and the magnetic pick up screw was loose.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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IMO
if the cap is not concentric with the center of the rotor, for whatever reason, the firing gap will vary as the rotor rotates. Like if the shaft is bent or the spindle. Most coils will handle this no problem, yours may not. If the spindle is bent, the points may not be opening on certain cylinders.
Or it could be a bad wire or mis-gapped plugs, and the rotor gap is just the straw that broke the camel's back.
So what I would do is isolate the affected cylinders,and check the point-gap on those cylinders. If the points are at least opening, then I'd check the wires and plugs for them, perhaps swapping good parts from known to be working OK, other cylinders. Of course if the problem follows the plugs or the wires, well then I'd replace them with new parts. But if no change, then it has to be a bent shaft, IMO.
To prove it,if it isn't obvious, I would pull the D outta there and clamp it in a vice and watch it as I spin it.
If you can feel the rotor hitting the cap towers then something is bent for sure.
But if it's not bent, Change the coil.
Vertical motion of the guts in the D only varies the ignition timing of all cylinders equally and only to the extent that the oil-pump drive walks up and down; and that should only be because of a loose camchain. You can shim your D if you want, but if the Drive walks up and down, it will still vary your timing. The only way to prevent it is to mechanically lock the drive down, or eliminate the sloppy chain.
if the cap is not concentric with the center of the rotor, for whatever reason, the firing gap will vary as the rotor rotates. Like if the shaft is bent or the spindle. Most coils will handle this no problem, yours may not. If the spindle is bent, the points may not be opening on certain cylinders.
Or it could be a bad wire or mis-gapped plugs, and the rotor gap is just the straw that broke the camel's back.
So what I would do is isolate the affected cylinders,and check the point-gap on those cylinders. If the points are at least opening, then I'd check the wires and plugs for them, perhaps swapping good parts from known to be working OK, other cylinders. Of course if the problem follows the plugs or the wires, well then I'd replace them with new parts. But if no change, then it has to be a bent shaft, IMO.
To prove it,if it isn't obvious, I would pull the D outta there and clamp it in a vice and watch it as I spin it.
If you can feel the rotor hitting the cap towers then something is bent for sure.
But if it's not bent, Change the coil.
Vertical motion of the guts in the D only varies the ignition timing of all cylinders equally and only to the extent that the oil-pump drive walks up and down; and that should only be because of a loose camchain. You can shim your D if you want, but if the Drive walks up and down, it will still vary your timing. The only way to prevent it is to mechanically lock the drive down, or eliminate the sloppy chain.
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is it missing at idle only or through out rpm range if idle only it could be carb related #1&7 far from carb do they share the same side of carb it takes a hotter spark to fire a lean mixture and more timing.
furrystump
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I had slight flutter and discovered that my rotor was sitting to high so it would arc to to roof of the cap terminal not the verticle face. Ground a little off the bottom of the rotor allowed it to slide down on the shaft a bit more. Flutter gone and arc witness marks in the verticle surface.
furrystump
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Some rotors are a touch short in length so if the path of least resistance is up you can have issues.
I am wondering about the condition of the plug wires. Maybe you accidentally damaged one.
If that is an arc inside rotor,chuck it.
Scratch that. Arc is on cap now that i look closer.
The greater the distance your arc has to travel through air , forces voltage up. You may have bad wires,requiring more voltage to light the plug. Tweaking cap increased air gap making voltage climb.
Check the plug gaps too.
Scratch that. Arc is on cap now that i look closer.
The greater the distance your arc has to travel through air , forces voltage up. You may have bad wires,requiring more voltage to light the plug. Tweaking cap increased air gap making voltage climb.
Check the plug gaps too.
rustycowll69
Well-Known Member
I've seen the dist lead get pinched between cap and dist body, cocking cap at an angle. I've seen similar thing happen with cap missing key slightly. I've also seen rotor contacting inside of cap and blowing it into pieces. It's pretty easy with rear mounted dist to get sloppy and not place cap on evenly, because you may not be able to see it easily and it can be quite a reach. I've also seen putting the cap on crooked, where the rotor''s thin center contact bends around the center contact on the cap, so it's riding on the side edge of the contact, not on the center, even though the cap looks, on the outside, to be located on the dist body properly.
Do not buy a clear cap. I did and now could clearly see how badly it was made. I had to solder an extension onto the rotor to take up the excessive gap.
It’s just strange. I haven’t had it run long enough to notice any carbon or build up on the cap or rotor both look about new. Have all the wires and coil replaced. Cap and rotor look new. Cap is new. It’s not when I push on the distributor it’s just the cap. I’m wondering if the cap is just Junk or mos aligned or if the original distributor wiring is crap. I did pull this car out of a barn it’s been sitting forever. Been chasing issues all over. Put head gaskets on it all seals finally I think it’s all sealed now I’m wondering if I should just get a new distributor unfortunately I can’t afford a good msd one. The cap does seem off when I put it on tho. Like the clips are kinda crooked I guess here comes the parts cannon
Vehicle is misfiring at all rpms. I have a spark tester and the front two cylinders are the worst this whole points distributor and carb stuff is all new to me. The only thing that hasn’t been replaced is the distributor and spark plugs. They are pretty new but decently fouled from misfiring so badly and me getting excited and trying to drive it
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