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L20b EI Matchbox Rotor Phasing / Distributor install Question

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Referring to google images for proper distributor installation and found something interesting...

 

Some guys install the distributor with vacuum advance point toward drivers headlight, sone install it 180 deg out, with the vac adv point to thermostat area. 

 

This is cause by install the distributor pedestal backwards, or correct. (correct way is vac adv pointing towards driver headlight)

 

Now I've also referred to several manuals I have from the 70s... Many show cylinder 1 on the distributor cap as theforward most plug on distributor. However, no matter what I do, cyl 1 on distributor is actually the rear most plug on cap. 

 

This is determined by oil pump installation orientation with the "small" part of the Tang forward. This is how the manual says to install.

 

 

Thought....?

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Some matchbox distributors have the vacuum advance just clockwise from the matchbox, others have the vacuum counterclockwise from the matchbox.

My first matchbox distributor did not come with a pedestal, and I had to use the L-16 pedestal and modify the clocking plate.  Then the rotor pointed in between two plug wire towers, with the bolts in the clocking plate.  I dropped the oil pump, and turned the drive spindle to make the distributor rotor clock with the distributor body position.

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Sorry if my original comments didn't make sense. I was in a morning meeting at work and had to type fast........

 

So, my over all concern is rotor phasing. Maybe I'm thinking too far into this, but, all the little things matter in the big picture. 

 

 

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Basically what Daniel said....

Honestly as long as you have the #1 cylinder at top dead center where ever the rotor points becomes the #1 plug... follow firing order and you'll be fine some of the distributor pedestals are different... 

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44 minutes ago, Crashtd420 said:

Basically what Daniel said....

Honestly as long as you have the #1 cylinder at top dead center where ever the rotor points becomes the #1 plug... follow firing order and you'll be fine some of the distributor pedestals are different... 

 

This.

 

As long as it runs and you have ample room to adjust your timing it's fine. I have the vacuum advance almost into the rad hose to keep the matchbox away from the hot exhaust.  

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Its easy enough to grab a  12mm socket and drop the oil pump to set it up per the book.  Or move the plug wires.  

 

BUT... phasing CAN be off.  Put 4 marks on the distributor housing that line up with the cap terminals.  Then pull the cap and verify when the distributor should be firing (10-15 BTDC at the crank) that the rotor overlaps the cap terminal its firing to.  You don't want the spark jumping off the corner of the rotor, or it'll burn out quickly and also cause tons of RFI noise that will ruin your ignition signal.  The short of it is that you'll likely have to re-clock the drive gear by dropping the oil pump, if this is a new electronic distributor put in place of a points distributor.  You may also find that you MUST get the electronic distributor pedestal to go with it or you may not get the phasing right.  

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I have a few caps laying around. I'll sacrifice and drill a hole in one to view rotor phasing. 

 

Some people are happy that their engine is running. 

 

I'm not happy until it's running correct.

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You do not need to do that to the distributor cap.  If you line up the four points on the rotor with the four points on the stator (pickup) the matchbox distributor fires each time the points meet, exactly.  You can put the cap rotor on the distributor, line up the points on the pickup stator and rotor, and use a felt pen to mark where the cap rotor is pointed on the distributor body.

 

The oil pump spindle drives the distributor shaft.  The spindle and shaft only fit one way.  The trigger four point rotor, and the distributor cap rotor only fits one way, and they move with the distributor shaft, but are moved advanced, or retarded depending on the engine RPM. 

 

You have a limited clocking ability with the distributor body, and the timing plate, and pedestal.   The oil pump drive spindle has only 18 or 20 teeth.  That means you can position the oil pump spindle in only 18 or 20 possible locations, 20 degrees, or 18 degrees apart.

 

The phasing in the distributor cannot be off.  The cap rotor and the trigger rotor are on the same shaft, and that relationship cannot be changed.  If the distributor body, and therefore the distributor cap are not lined up with the cap rotor, the pickup rotor and stator are also not lined up, and the distributor will not fire.

 

If the oil pump spindle is not indexed correctly, the distributor body may not line up the holes in the timing (clocking) plate between the distributor and the pedestal, or if you do get the pedestal, timing plate and distributor bolted together, the spark will occur nowhere close to TDC  

 

 

Edited by DanielC
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20 teeth or every 18 degrees on the spindle and 10 teeth on the drive worm gear. 

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Rather than go out to the garage late at night, I looked at a picture in an old Datsun book, and it showed two different L-16 distributor drives, one with two steel gears, and one with  a brass gear and a steel gear.  I believe the spindle in one picture had 20 teeth, the other spindle picture has 18 teeth. 

 

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The brass ones are highly sought after by racers.... I don't see why. Supposedly they wear less or there's less slop.

 

The 18 tooth would need a special 9 tooth crank drive worm gear. Well my parts manual shows the 510 only having two part numbers for the 510 spindle and worm gear. The second number is used on all other L16/L18 and L20B and even on a Z20/22 and Z24 engines. Interesting....

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The phasing CAN be off.  We don't even know which distributor he has yet.  The wrong vac unit could be installed with a different arm length.  4 versus 6 cylinder.  Different pedestal,  different clamping plate, etc...  If there's one thing I've learned rebuilding distributors, its that people mix and match parts where they don't belong thinking it doesn't matter.  A1 Cardone is the largest offender.  

 

The 9 tooth cam has a better gear angle and does wear less.  Bronze gears are used as a sacrificial component so the cam doesn't get damaged.  Their tensile strength is almost as strong as 4130 steel, but they are quite forgiving.  Historically, they have fewer failures which is why both Datsun and MG racers search them out and have even reproduced them.  

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I will run a worn out part before I buy a A1 Cardone piece of shit part.

 

I know the stock 1980 720 L20B matchbox distributor mounts with the with the matchbox facing the radiator as Mike said his was.  I have pulled several matchboxes from L20Bs from cars late 70 510s and the matchbox was facing the carb.  Not sure if the 510 matchboxes were installed properly or not.

 

Distributor Guy I am wondering if there is any difference in the 1980 720 L20B disributor for a five speed and automatic.  I have the 5 speed matchbox in my 76 L20B with the 3N71B automatic.  Should I have the 5 speed matchbox reworked for the automatic?

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The '80 2wd show two different vacuum advance part numbers for standards and auto. The governor weights and springs are the same so maybe just the advance for part throttle.

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My worst case distributor set up.  A matchbox distributor, no pedestal, no timing plate, use stock L-16 point distributor timing plate, and pedestal.  

First issue, the hole for the distributor body bolt on the timing plate does not line up with the matchbox distributor.  Solution, cut that side of the timing plate, space it out to the larger diameter of the matchbox distributor, weld it back together.

Second issue, using the factory oil pump spindle location, about 11:25, smaller half forward, with both the pedestal bolt and the distributor body bolt about centered in the timing plate, the cap rotor was pointed almost exactly half way between two plug wire towers.  The solution for this was to drop the oil pump, and reclock the distributor drive.     

 

 

 

My point was you really do not need to cut a distributor cap to check the relation ship of the trigger rotor and cap rotor.

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7 hours ago, DanielC said:

 

 

My point was you really do not need to cut a distributor cap to check the relation ship of the trigger rotor and cap rotor.

 

You're really hung up on me drilling a 1/2" hole in a used cap arent you?

 

This is a trick all racers use. I'm sure you know this.

 

Drill a hole and view with a timing light. Helpful trick I learned when I was working at Blood Enterprises - a hotrod fabrication and tuning shop in Auburn,  WA.

 

When I take my B210 / LZ23 project to Blood Enterprises for tuning, they'll most likely remove distributor and spin it up on the old Sun Distributor machine and correct the timing curve. And without doubt he'll check rotor phase anyway. I just have to make it run good enough to idle.

Edited by mhub91
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On 7/26/2018 at 8:00 AM, mhub91 said:

Referring to google images for proper distributor installation and found something interesting...

 

Some guys install the distributor with vacuum advance point toward drivers headlight, sone install it 180 deg out, with the vac adv point to thermostat area. 

 

 

 

Thought....?

 

 

The reason is is because some like to keep the ignitor box farther away from exhaust heat.. Whether it's warranted or not i don't know 

 

 

You're welcome

 

/

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Thanks Mike I will look up the part# for the automatic vacumm advance and install it when it comes in.

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2 hours ago, bananahamuck said:

 

 

The reason is is because some like to keep the ignitor box farther away from exhaust heat.. Whether it's warranted or not i don't know 

 

 

You're welcome

 

/

 

 

Yeah, thats what it seems. 

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13 hours ago, Charlie69 said:

Thanks Mike I will look up the part# for the automatic vacumm advance and install it when it comes in.

 

You won't notice a difference between how the two different vac units operate.   Its a minor shift, and as much as vacuum changes with state of tune, its tiny.  Adding a little bit more tension on the advance springs (+1/16" stretch or less) will do more for drivability.  

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If you install the  the oil pump spindal per the instructions at TDC . if pretty simple. Line up the dimple on spindle to the pump dimple(or as on my YOUTUBE vid) the pump drive will comeut in the 11 28 position. ir pretty dam close.

 

Install the mount and hopefull you put it back in the same way it came off and not 180 degs. which will still work but the vac adv might be in the 180 off location.

 

Now install the dist dist and it will lock down in its position. this will be # 1 plug.  One will assume you have the dist slightly loose and maybe even the 8mm bolt holding the dist plat loose and have it free enuff to get the middle adjustment..

 

start the motor and seet the timming to say 10-12 btdc.  What I do once running is loosen the bolt and turn the dist to see if it goes betweeen 25 BTDC to 0 . if you have that wide of a adjustment you pretty much have it at the right spot to final tune it and have room to load test it on a hill to make  to see how the mechanical adv is.

 

No need to make a hole in cap as you have a light to show this where its position is anyway. I guess one can take a old cap and do this for new people to understand ezer. as soemtimes it take a few trys to get the oil pump spindal correct when fisrt install the pump and spindal.

 

 

where the rotor points at front or back dont matter as a L16 set up might be diffent from a L20. Long as you know its TDC and then go 1 3 4 2 fire order.

I have a idiot said he had to drop the oil pump and turn the spindal cause he was out 180 deg. I said. just move the plug wires 180deg.  But this was the same guy he said he had special motor mounts for the L20 in a 521 to raise the motor so the oil pan clears. I told him whydont you use a 521 pan. He had a big ?????? mark look on his face!!!!!!!!!!!!

 

also on the matcboc dist . there was 2 versions and if one uses the wrong mount cause they grabed just the dist and not as a set the TDC roto position can be off between plug wires 1 and 3 thus giving a  very off timming where it will start but run out of timming at higher speeds. But if one has a timming light one will see if the distributor is cranked to one side to get the timming in spec. This is why one should go between ) and 25deg by turning the dist when running to see you got the max timming slot movment

Edited by banzai510(hainz)

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