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Electronic Distributor Upgrade - Low RPM/Load Misfires


BrandonS

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So I upgraded my old points distributor to an electronic distributor.  I had a lot of trouble with it due to not having the correct pedestal.  I flipped the one on the car and got it to mount with the ignition module away from the header.  I am now at the point that it starts, runs, and drives; but I'm getting a stuttering misfire when putting the car under load at lower RPMs.  When I time it out at idle, it's sitting at 12 BTDC.  When I run the revs to around 3k it's showing right at 20* advance.  This is all with the vacuum advance attached.  All the plugs wires seem to be on tight and the coil wires are tight as well.

 

Here is what I have for timing marks.  I'm using the hot pink one as the TDC mark.  So to set the engine at 12* BTDC I am putting 12* advance on my timing light and then lining it up with the pointer.

 

N7tiZwJ.jpg

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I still have the ballast resistor wired in and have a new coil.  It says on it to use it with an external resistor.  It's an Airtex Wells 5C1057.  The plugs are the same plugs that were in the car with the points distributor and are in perfectly fine shape.  I do have another set of new NGK 4006.  The distributor was a brand new reman unit from A1 Cardone.

 

Oh and it also will do tiny little burbley backfires when decelling.

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So I just went and double checked everything.  All the connections on the coil, ballast, distributor, and all the plug wires are good.  I took it for another spin and same thing.  Sputters and hestitates under light load 2k-3k RPM.  I can say though, it has a lot better top end than it did before.  I also put the old coil in since it's wired the same as before with just a 12v signal running off the ballast to the distributor.  It did the same thing with both coils.  I also had the valve cover off and verified that the cam lobes were at 10 and 2 when the TDC mark on the crank was lined up.  I wonder if it isn't maybe off a few degrees and my real timing isn't 12* BTDC as I'm measuring it.

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They were a nice golden brown color when I had pulled them out before putting the new distributor in.  I tried to do a quick adjustment on both carbs right before going out the second go (I went twice), but it's still missing.  I'll let it warm back up tomorrow and adjust the carbs. Then go from there.

 

It runs fine 90% of the time.  I'm getting the misses when I'm driving super slow in 2nd gear.  If I'm just creeping along on a side street and need to accelerate I almost have to downshift to get the revs up to 3k to not have it miss.  WOT above 2500 is perfectly fine and pulls better than before.  It's baffling to me.

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Dual SUs. They were recently rebuilt. Tuning them is fairly simple so that'd be a nice surprise. The only other thing I can think is I dropped a plug on the ground. Maybe it cracked the ceramic. That's a long shot though.

Was the rebuild of the SUs before or at the same time as the dizzy swap?

 

Also what motor?

The Ngk 4006 are br5es plugs.... is that recommended for the motor?

Maybe those are too hot of a plug?

 

Might be worth swapping to the new set of plugs and seeing if anything changes...

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How is the electronic distributor grounded? 

"Sputters and hestitates under light load 2k-3k RPM."  This sounds like fuel problems to me.   On the other hand, misfires when the throttle is opened from low speeds is commonly more of a symptom of ignition issues.

 

Spark plug readings tell you more about fuel mixture at WOT, under load, at higher RPM.  

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Was the rebuild of the SUs before or at the same time as the dizzy swap?

 

Also what motor?

The Ngk 4006 are br5es plugs.... is that recommended for the motor?

Maybe those are too hot of a plug?

 

Might be worth swapping to the new set of plugs and seeing if anything changes...

 

 

Was that before it ran funny or after? Have you checked for vacuum leaks?

 

The engine is an L18 SSS (assuming it's the original engine of the car).  The SUs were rebuilt before I had bought the car.  I don't know how long before, but I believe it to be relatively close to when I bought it.  The gaskets and condition of all the linkage look(ed) brand new.  Everything was working perfectly before I swapped out the distributor.  Car was running great really.  The reason I swapped it was because I needed a new rotor/cap on the SSS distributor.  I figured I'd just upgrade the distributor to electronic to avoid messing with points.

 

How is the electronic distributor grounded? 

"Sputters and hestitates under light load 2k-3k RPM."  This sounds like fuel problems to me.   On the other hand, misfires when the throttle is opened from low speeds is commonly more of a symptom of ignition issues.

 

Spark plug readings tell you more about fuel mixture at WOT, under load, at higher RPM.  

 

I don't have the distributor grounded other than it being mechanically bolted to the engine.  I've seen where they have a "tab" just above the vacuum advance, but mine only has a bolt.  I could run a ground to the engine block from there, but I feel as if a ground problem would show up more than these isolated circumstances; I could be way off base on that.

 

I was hoping to get at this again tomorrow AM, but the wifey informed me we have some family plans.  When I reattack this, I'll recheck the timing and maybe run it a few degrees in both directions in the event the timing mark isn't right for some reason.  I'll also readjust the carbs and swap the plugs out.  The carbs are super easy to set so it only takes a few minutes of fiddling around.  If I can't get it maybe I'll just see about throwing in a Pertronix unit into the old carb.  

 

Thanks for all the suggestions to look into.  Hopefully I can get this sorted out.

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Spark ALWAYS searches for the easiest shortest path to ground. What you have to do is make that easiest path the electrode on the spark plug. To do this, your coil, wires, cap and rotor must be extremely insulating. Any fault, damage, dirt can be the crack that lets the high voltage escape. Check you coil high voltage tower for any fine cracks or carbon tracking. Carbon tracking is a mark on the surface that looks like a jagged lightning bolt. It's fine as a spider web and is caused by an electrical arc. Once made, it's easier to use again. The distributor cap and rotor may also have one as may a spark plug. Old plug wires can break down with age and exposure to heat and oil so inspect them and the nipples. It's harder to fire a spark plug when the engine is under load. It requires higher voltage and if this exceeds the ignition systems ability to contain it you will get a misfire.

 

You said that the timing went to 20 degrees when revved to 3K???? Static and mechanical advance should total over 30 degrees by 3K. Or is this with the 12 degrees dialed in?

 

Well 90% of carb problems are electrical and 90% or electrical problems are carb. So take it out for a spin and get it into the sputtering mode and gradually pull the choke out to richen the mixture. Does the miss go away????

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The points coil is about 1.5 ohms and is in series with a 1.5 ohm ballast for about 3 ohms total when running. If using on a matchbox, as long as you keep the points coil and the ballast together, it will work just like the points... BUT you will have no increased voltage output, only the removal of the points.

 

If you run the points coil without the ballast, the matchbox OR the points will draw way to much power through it and it will most definitely over heat. Argueably you would have higher output voltage but the coil will eventually fry doing so.

 

An EI coil is 0.8 to 1.0 ohms and designed to handle the extra current drawn through it without over heating. The extra current makes a stronger magnetic field that when it collapses, produces a 'hotter' spark. If you have a matchbox you really should run the EI coil for maximum benefits.

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Was the rebuild of the SUs before or at the same time as the dizzy swap?

 

Also what motor?

The Ngk 4006 are br5es plugs.... is that recommended for the motor?

Maybe those are too hot of a plug?

 

Might be worth swapping to the new set of plugs and seeing if anything changes...

Wrong plugs B6ES 11  or BP6ES 11  Gapped at .040" - .0430  Use the proper coil WITHOUT a ballast resister

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Spark plug gap increases when going points to matchbox. .042 BPR6ES. BPR7ES would be one step colder.

 

 

And a brand new rebuilt dizzy is just a dizzy cleaned up with new grease packed in there. Cardone is not the greatest. Carry a spare dizzy if taking a road trip.

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have photos of this elelctrnoic ignition?  You can still use a point coil and ballast you just wire it like a Petronix for a more precise ignition timming and more reliable.  If a True electronic ignition timming you want you need to get a EI coil and bypass the ballast.  But I have never done this and just use a Pertronix with stock coil and ballast and never had a proplem. I don't see how coils go bad anyway. if rarely.  Maybe if somebody cooked the coil by removing the ballast resisitor.

 

I run stock plugs are stock .032 never have a proplem.

 

 

recheck your valve lash.

 

try 10 deg  with timming light.   with vac advanve line pulled.   then take distributor and turn it where you see it go to Zero and turn otherway to see it go to 20 deg. if it does then dist is like corrwect. Now if your dist is cranked all to one side to get 12deg then I bet its off a tooth and when you set it to the center position using timming plate it goes to say 25degs with light its obvios the spindal is off or you have the wrong timming pedestal.  there is  8MM BOLT ON BOTTOM TO MOVE THE TIMMING PLATE TO THE DISTRIBUTOR.  try fucking with it.

if this is all good then look at the carbs. I don't like SUs but I seen some great running ones.

 

 

Youtube has my Vids look up Hainz Datsun L series part 5 I think I show  installing a distributor.

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"And are the 2 front can lives pointing at 10 and 2 o'clock?"

translation:

And are the 2 front cam lobes pointing at 10 and 2 o'clock?

 

A matchbox distributor can run a points coil, with a ballast resistor, and plugs at normal points gap.  

Run a wire from the distributor body to one of the front bolts between the cylinder head, and the timing chain cover.

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