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L20B Timing Troubles


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Hi guys, I posted a little while ago about a no spark issue which you guys helped me resolve very quickly (thanks again). I have a 1971 Datsun 521 with an L20B and an electronic distributor which I purchased as a project and the previous owner had bought most of the parts from Datsun LLC or now known as California Datsun. I'm not going to get into all the troubles I've had with the shotty parts purchased by the previous owner through California Datsun just trying to figure out how to get this thing running right. As of now with my timing light set I have it at about 12 degrees initial timing and it idles great and then as you start to open up the throttle the engine starts to stumble at around 2,000 RPM and will not rev past that. I initially thought it was carburetor but am now leaning towards a timing issue as when I have my timing light on there while running as I increase throttle the timing will advance to about 20 degrees and then right when the engine starts to stumble the timing falls off. Here are some photos, I don't know if maybe the cam timing is off? or the oil pump/distributor shaft is off or what the problem is. Here are some photos of the various timing places the engine is set to TDC on the compression stroke for all of the photos, let me know if you need any other photos or photos that are more detailed/clear. Any help will be greatly appreciated. Thanks






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Hey wayno, yes it is at TDC Compression stroke, I wasn't the one who installed the cam so I'm not sure if the dowel is in the #2 hole or not, also was wondering how to check that? It is very possible the carb could need adjustment, the mixture screw is at 2 turns out right now and I have tried playing with that a bit to figure out if it was carburetor related as well but no matter where it was turned it didn't;t seem to change much. Carburetor is a 32/36 Weber with 135/145 main jets, 160/165 Air correction jets, 50/55 idle jets, needle valve is a 2.00. The accelerator pump works great I can see a nice stream with the air filter off and measure float height which is also within spec. Thanks

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That is not usually where the Matchbox unit would be, but as long as the rotor is pointed at number 1, and the correct firing order counter clockwise, 1-3-4-2, then you should be good for start up.

It's hard to figure little stuff out online, as one cannot see everything, but the cam looks good in the photo(generally speaking), and the rotor is basically in the correct area, I can only assume the valve lash is set correctly.

I believe my timing is around 6/8 degrees in my LZ23, it was closer to 10 degrees but I could barely hear it knock on warm days so I set it back a little farther.

Does it rev slow or normally?

The only way to see what hole your using on the cam gear is to remove the bolt/fuel pump cam and be careful to not let the gear come off the cam and look at which hole in the gear the dowel is in, it should be in #2, if it is not in #2, then it should be put together properly which is easy to do with it at TDC, but you need to use a timing chain block to keep the timing chain tensioner from popping out.

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I'm pretty sure that's pointing the correct way for a remote ignitor unit. At least that's how mine looks. And as wayno said, 1342. Make sure the carb is right too, maybe you'll get lucky and stoffregen will chime in, he's good with webers.

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I thought the same thing on the pedastal. Matchboxes had 2 types. This is written on Olddatsuns.com in the tech section I believe.


when the dist locks down when you install it it should be right on number 1 cylinder plug wire when you have dist cap installed. Now if its between 1 and 3 then your pedastal is wrong and one has to move the oil spindal by dropping oilpump and moving it a tooth over. or find the correct pedastal


the matchbox 1 model can use the point L20  pedastal(which is same for 1 model) but then there is another which moves the tang like 15 degs away so when you acclerate you go out of time..



one way to cheack what you have is take that 10mm bolt out and move the dist and lock it with a mini C clamp.


ck out my vid on youtube part 5 or 6  Hainz L series Datsun.



as for what hole your using on the cam gear what ever number is in the 2 oclock postion is what your gear is set to so you dont have to pull the fuel pump ecentric. Ypour cam gear is set to 1. L20s should be 2 but I wouldnt worry about it.



this is a simple fix  and lookes like a nice motor you have

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The problem could be just about anything at this point. But I'd start by verifying the firing order, then verify TDC and double checking the cam timing. Check that the carb is tight on the manifold and there's no vacuum leaks. Unless there's something wrong with the carb, it should still run up past 2000 RPM's, even with improper jetting. The control box on the distributor could be bad too.


Wrong pedestal aside, if he's got 12 degrees of timing, it's still 12 degrees. No matter where the rotor is pointing or what pedestal is installed.


It's hard to tell from the pic, but to me it looks like the mark on the cam gear is behind the mark on the cam thrust plate. If so, that's not right. Have you verified TDC with a spark plug removed?


One of these days I need to do my own video of how to check cam timing with a dial indicator. It's the easiest way to guarantee the timing is right, without having to rely on the marks on the cam gear.

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I think Mike's question is probably bouncing on the real issue.  If the timing is good at 12, and then is advancing as RPMS increase, then goes haywire as the engine misses, its something in the dist.  Cam timing would not be involved.  Pedestal, while it may be incorrect, shouldn't create the issues he is describing.   Module from a z - lots of documentation of weird running issues with those.   

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he might have the dist cranked to one side to get it started.  now if he gets 12degs and the dist is still close to the center of the plate or slightly advanced then its soemthing else other than the timming.


I will assume he has a EI coil also. since he has a matchbox installed



to me everything looks ok .   Cam spocket and intake exhaust lobes look correct and dist spindal timming is correct.


cheack the valve lash



Not positive on the rotor pointing to #1 plug wire, but you can cheack that.



watch the vid!!!!!!!!!!!!!



I think I see the proplem!!!!!!!!!!!! look at the rotor very closely.(made in China)

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Hey guys I just got home from work, thanks so much for all the replies. To answer some of the questions; in order for me to get the truck to run halfway decent and idle I have the distributor maxed out on the adjustments, when it is at TDC compression stroke and I take the rotor off I cannot get the teeth on the inside of the distributor to line up at any adjustment, also it is indeed a El coil and I have adjusted the valve lash and it did not help my problem. The numbers on the matchbox are E12-80 and the numbers on the side of the Distributor are D4K9-01. When I bought the truck everything had been torn apart and I have put everything back together so I didn't have a lot to refrence and I'm not sure if that is the correct distributor base or not. Haha I know (made in china) doesn't belong anywhere near this thing!!! I'm going to watch the videos and see if i can remove the adjustment bolt on the distributor base and clamp it to get it to run proper. Thanks again everyone you guys are awesome.



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E12-80 is good

22100-04W00 is a 1980 720 truck L20B distributor... also good.





If you are maxed out on the adjustments for timing you will have to remove the oil pump (4 bolts) let it drop down. There is a spindle above it that also drives the distributor... you can see the top in the picture. It's gear driven and needs to be dropped down turned one tooth clockwise and put back in Looks like it's at 11:28 so try 11:30-ish. Note that there is a small half moon on the left and a larger on the right. With it moved over one tooth the distributor will be advanced an extra 9 degrees and should now adjust properly.

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Once again you guys saved my day. Ended up spinning the distributor and clamping it with a set of vice grips and the motors revs up fast now and revs past 2,000 rpm!!! I think I'm going to reset the oil pump so I can make this pedestal work with my setup or maybe I'll search for the right pedestal. Thanks again everyone!

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soembody might have a pedastal.

another way to know your off is when using a timming light when you retsard the dist you should be able to get past zero on the timming marks with the light and up to say +25deg/ if not then the spindal or pedastal is off.



when have to ASSUME the correct stuff was on there before so you been running it like this for awhile. whech confuses us

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Oh dude perfect Japanese classics... I get lots of looks when I haul my 75 yamaha Rd350 around also


oh one can adjust the timming also underneath the dist is a 8mm bolt that one can loose and re adjusted the timming plate. so it might help. also I seen soemtime people flip that timming plate and it might work also. But it you flip you might have to move the spark pug wires 180 deg. But it shows it on my youtube vid(hainzL series datsun chapter 5 or 6)

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