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L16 to L20 swap


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1 hour ago, Figbuck said:

...her is my fresh L16 head from two years ago.


The header that was on the L20, has little duct like things at the top of the header port. Who ever took the manifold off cut these little things jagged with a hack saw. 


I will have to take more oics when I go back out to the farm. 





These pipes


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Them be the ones... that used to be anyway. That plenum thing is long gone and the holes are plugged.


If I use decide to use it, should I grind all the casting that house those little pipes, and clean up the inside of the header right there? I'll have to look at it again now that I see what it was like. Chuck the Aluminum Head guy described the system working by having those sheet metal pieces in the head glow to help burn emissions. 


If I used my stock '73 header, can I use the L20 intake/exhaust gasket? I'm not at the farm to look. I can visualize a L16 square port gasket working better?



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  • 3 weeks later...



I got it all back together, but it won't run! 


It doesn't seem like it running gin time, it's back firing through the carb intermittently but won't run.


I used the Intake manifold from my L16 with a new Weber that ha been running for 5Kmi. Pulled it off the L16 and put it on the L20.


I used the square port L16 header with the L16 square port manifold gasket.


I use my starter and fuel pump off the L16, because they are new.


But I used the L20 alternator because it fit the L20 bracket, and it's a smaller unit than the later 720 alternator I drilled out to fit the L16 bracket. 


I used the electronic distributor that was on the L20, and it's coil. I tagged and numbered the plug wires when I pulled it apart.


I noticed at the time the the L20's distributor had the Matchbox and vac advance to the front of the vehicle. I have been running basically the same matchbox distributor on my L16 for a few years... but the Matchbox and vac advance are to the REAR of the distributor. I remember when I finally ditched the points dist.. I couldn't get the electronic distributor to run, until I dropped the spindle drive and moved it. #1 in the firing order started in front on L16s, not in the back like the L20.


Could I have the oil pump/distributor spindle drive out out time here...?



As I put the engine back together, I bolted on the timing marker to check if it read 0 when the #1 & #4 pistons were up. The dot on the crank's timing sprocket was @ 3:00.  The cam sprocket was installed on the #1 mark with the timing index mark straight up and the #1 intake and exhaust rockers were pointing up. Unless I accidentally moved the crank, I though it was an in time engine.


I can turn the crank pulley mark to 0 on the timing marker... TDC... and find a place in the cycle where the #1 cam lobes are up and the #1 on the cam sprocket is 2:00. 

 Isn't that an in time engine?


When you look in the distributor "hole" the tang on the spindle drive was 11:25.


Is it possible to have the tang 180 opposite... and still look like 11:25... the tang offset turns the distributor still, but orienting it backwards??


I though there was a marker on the spindle shaft and and small oil hole? I'm pretty sure I remember lining up the marker.  It can only go in one way if it's at TDC at 11:25 right... or not?? 


I'm getting compression... new rings. I'm getting gas, new fuel filter... I can work the throttle to see, hear and smell fuel in the primary. Can't back fire through the carb with out spark and fuel. New battery that cranks like mad. I swapped out my cap and wires, also the coil...  from the running L16... never had a coil go bad. But it's a different could on the L16 points distributor. 


I figured that the distributor came off a running engine, it could' be that far off. I loosened both the base plate and the indicator bolts so I could move it for the initial fire up. They were both all the way advanced to the right. No matter how retarded or advanced it still won't run.





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When I first tried to start my 720 with the weber on it it backfired and stuck the choke plates solid on the carb.  I would check to make sure they stay free.

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I don't know the Datsun motors very well, but from your description (backfiring through the carb) it sure sounds like it is out of time. Double check, and triple check your timing sequence. Maybe 180 out? I know you brought all these symptoms up, but my experience is that sometimes the simplest things that will cause the problems.


Once I spent several hours on Dad's 1973 620 (died in downtown Albany) and once I replaced the rotor it started right up. We had been to Ukiah, Oregon the day before, which happens to be many miles from the nearest town with any parts stores.



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Firing order 1342 counter clockwise direction on the distributor. Usually 2 and 3 are reversed.



There are 2 TDCs so make sure that you are on the compression stroke with the front two cam lobes at 10 and 2 o'clock then set the the notch on the crank pulley on the 0 (zero) on the timing scale, usually on the alternator side. Turn up to TDC moving only clockwise and stop. If you over shoot the mark, which is super easy to do, back well up before and try again. Do not set TDC by moving the crank counter clockwise or you will introduce chain slack to the tension side and the cam timing inspection will be inaccurate. With the crank now at TDC look through the top hole on the cam sprocket and down in behind it. If the cam is properly timed you will see this...




The notch in the rear of the sprocket should be below and slightly to the right of the small horizontal line etched into the cam thrust plate behind it, as shown above. The above picture is an L16/18 and set on the #1 hole. L20Bs come from the factory on the #2 hole so you may find your notch is to the left. If so, block the chain tensioner so it can't fall out, and move the sprocket to the #2 hole. This will move the notch 40 to to the right.... about the width of the etched line. When you L20B sprocket looks like above the cam timing is correct.




Now that you are perfectly at TDC pull the distributor and it should be at 11:28

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Right, my cam sprocket is set just like that, you can see the index mark... but what I'm saying is the marks on the chain, are line up with the #1 on the outside of the gear. You can see the #2 mark in the photo... so that the #1 is at the 2:00 location. And it doesn't show it but the mark on the chain is on the #1 tooth. 


How can the crank sprocket be off if it reads 0 on the the timing marker... the chain mark is 22 links away from the cam sprocket mark on the #1 mark on the outside of the cam sprocket. 


Look at my photo... distributor tang is at 11:25... 0 degrees on the crank pulley mark and #1 cam lobes up.

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OK, I am late coming into this thread, some observations, see this head in the photo below, this is a terrible way to store a head, it is likely resting on a valve and can bend said valve, the cam appears to be in the correct position, I hope no valves were bent.



If your putting this head on an L20b block you need to use #2 dowel hole on the cam gear, the little notch like in Dmikes photo needs to have #2 straight up on the gear(not #1), the little notch needs to look like it does in Dmikes photo when the cam gear is installed, the crank pulley notch needs to be on 0 degrees.



Next you need to look where the rotor is pointed at on the distributor cap, it should be pointed directly at a spark plug wire post, that would be number #1 plug wire, the firing order is 1342 counter clockwise direction on the distributor, if the rotor is not pointed at a post on the distributor then it is not set up correctly.

I am going to pick up a telescope tomorrow up in Anacortes WA tomorrow, it will take all day, I have work Monday, Tuesday is the soonest day I have if you want me to help, I have no work scheduled Tuesday, I can usually get an engine running if it is going to run by eye.

Keep in mind that if a valve is bent in that head it will never likely run right, it will backfire out the carb or it will have an exhaust miss, but backfiring out the carb can be that the distributor is 180 out or you have the firing order set up clockwise, I always go back to the basics, crank at TDC, cam lobes at around 10am/2pm, rotor pointed at around 4pm looking at it from the side of the truck, it should run if everything else is good.

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Thanks for the input. 



I'm going to rent a van in a few minutes, so I can run for parts and stuff, go back out to the farm for a couple days. I'm really burned out from this, dozens of hours cleaning and fixing stuff. I'm going to get a big table set up so I can drain the fluids and take it apart really fast. At least I don't have to clean that much. I'm dreading having to take the crank pulley off again, but I have never been able to move the timing chain with a block. I'll order new timing gaskets and do it over. Half the time the tensioner comes out and unless the oil pan is off so you can get to the crank sprocket to pull it down off the sprocket and try to move it.


I'm not where I can look at the engine, but there is no internet out there, I'm lucky to have electricity.


So is the matchbox and vac adv on the front of the engine or to the rear on an L20?




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Your going to tear the engine apart, you don't need to do that, put it at TDC using the rotor to confirm, then check to make sure the cam is at around 10am/2pm, now if the rotor is not pointing at one of the distributor posts when the crank is at TDC and the cam lobes are at 10am/2pm then the oil pump will need to be dropped to re-set the distributor drive shaft so the rotor is pointed at a spark plug wire post on the distributor cap.

I can move the cam without turning the crank as long as it is not too far off.

I biggest mistake most make is putting the spark plug wires on the distributor cap clockwise instead of counter clockwise.

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It's apart now. Just drove back into town to get parts and stuff. L20 gasket kit was $13 and will be here after 2:00. Yeah, somehow the chain must have slipped a couple notches on the crank... but what's weird is that there is a place in the cycle where the timing marks lined up! But it doesn't run, I fucked up somehow.


I did learn something. I made a jig/fixture out of a piece of aluminum shelf bracket, !" x  5" x 1/8" thick, to keep the flywheel from turning when I torqued it on. I used the same piece of metal, using one hole and drilled another hole the size of the bolts that fasten the starter motor. I positioned the holes so the little plate covers most of the teeth on the flywheel, but not at the bottom... so I could wedge the blade of a strong screwdriver  against the plate between the engine and the bell housing. It's like having an extra hand. I popped the 27mm crank pulley nut off the first try with a 1/2" breaker bar. 



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I think you didn't need to take this apart!!!!!!!!!!!


if anything you just off a tooth on the dist drive  crank the dist one way or the other and see if starts.



I thought my video explanes all this


who makes that Cam timing Gear??????????




put motor crank at TDC.  then cam will be set up if done right. 

dist spindle will be about 11/28 position. installe the dist pedestal/mount. You can install it 180 out if you want the vacuum adv in a better place.

when the dist lock the rotor should point a a plug wire.  pretty much right on when the playe is centered. Then put on the plug wires 1 3 4 2 CCW..

Don't go by the oldl16 distributor as it make be oppisite


didn't need to take apart? WHAT YOU TAKE APART????????



if that don't work sell as scrap

Edited by banzai510(hainz)
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Hainz, I wish I would have watched that while I had it on the stand. I watched it a few times years ago. I forgot about your videos, but mostly I have been out at the farm, glad to have electricity form a 150 extension cord. No running water, no internet. It would have been fantastic to watch your videos as I was in the process. 


You are probably right. I didn't need to take the timing cover back off, but a new gasket set is $13. I did fixed some things where I didn't like the way they turned out on the timing cover. But going through the process again, I realized I set the cam sprocket on #1 marks... I've been working the the L16 so long that I checked and double checked... to make sure it was on #1. Big time brain fade. I really don't think I could have moved the cam sprocket that far to line up with the chain marks. I just haven't been able to do it with out the tensioner popping out.  But like you say, along as the crank is TDC, the slack is out of the chain and the cam sprocket is set right, will run.


I've been getting all my parts from the NAPA in Newberg. It said made in Japan. The chain didn't have the two light colored links or even marks. I drilled the dimples in the photo myself. 


After I put oil and coolant back in, pulled the throttle cable to turn on the choke, reached in the window to it fired off... with one stab at the starter... idled right at 800! I put a timing light on it, then took it for the old Hasting's Ring road test to seat the new ring.  Accelerate from 35 to 55, ten times. I came back, checked the valves, tightened some hose clamps that were seeping. In the words of Colin Messer: "I don't know if it really works or what... but it feels good to do it. I remembered reading the instructions 30 years ago on the Hasting Ring package, when I built the L16! It did feel really good! New clutch, yeah! I could feel the extra displacement and torque. I like the way the alternator whines  with the sound of the valve train, and the intake snort of the Weber is louder too. 


I put the hood back on, buttoned up some other little projects and cleaned up my horrendous mess. I drove into town to get some hot food and gas. I looked for leaks or problems when I stopped. Everything seemed good to go, so I started to drive 20 mile into Portland. I got a mile from home when started to smell coolant. I look for a place to pull over with a street light, but before I could stop, a geyser of coolant and steam came blowing out from under the hood. AHHHH! Terror! The top heater hose had a rip in it! I got all new radiator and heater hoses, but I didn't change the heater hoses yet. I'm going to pull the heater and clean it soon, so that was a project for another day, I was really trying to get the swap done and running. 


Fortunately I threw a small box of tools, in the truck so I had a pair of Vice-Grips, a fifty cent piece and a big washer, to clamp the hose off, then shut the heater off. A guy stopped to see if I needed help, so I gave him my empty water jugs. Got to take drinking water out to the farm, haha. He came back in a minute with water and hung around to see if I could get going. He said he has an old Toyota with a camper shell that he keeps running, so he had to rescue me. Followed me home to see I made it. What a nice guy, restores your faith in humanity.


I'm really happy. After losing my best friend to cancer in July, two of my high school girl friends died weeks apart in February, one in a house fire and the other from a brain aneurysm...  I'm just trying to be in the moment and not stress over shit too much. Life is too short. If this engine last me thirty years... and you can still buy gas... I will bet 98 years old, owned the 620 for 77 years.  I think it was pretty cool that I pulled the L16 out and dropped the L20 back in all by myself... what could have gone wrong there?  


Thanks for responding to this thread Y'all. I will post pics. Add up the hours and parts cost...  





Edited by Figbuck
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If you had Cam on number 1 or number 2 is really no big deal. L20 it might be more emmissions anyway.  power comes on sooner the more you advance the cam.


yes on motor PULLS the hose tend to crack and break cause they been at a steady state for years then when one takes motor out  they crack in the rubber  cracks inhard spots.  I just had a heater hose go bad lucky is was right that the end I just cut it off and stretched it back on the fitting!!!!!!!!!

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  • 2 weeks later...

I need a new exhaust system so I took it to Exhaust Specialties in Beaverton. The mechanic said the flange on the pipe was too thin to weld to. I also noticed the 4 into two collector is hitting the corner of the block. I guess a 3/4" taller block pulled it up. I cranked down on the new exhaust studs pretty hard, but not so hard somebody has to fight them when they go to work on it.  He noticed that the header to the collector joint was leaking around the new gasket. 


Any suggestions? 

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Cut the flange off, adjust the tubing so it doesn't hit the block, and then weld on a new flange. Someone here sells new two hole flanges, or you can scab one off another application from a wrecking yard, or you could whittle one out of steel. I think muffler shops have a good source for new flanges too, so maybe you shop can get you a new one, or even a pair.


All that work and it may be easier to get a different header. Is it actually a header or is it a cast iron manifold?

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I think it might be easier to get another header. I'm striking out finding a flange for that '73 square port header, can find them for L20 and some other Datsun applications. 


I remembered that Mike Klots made some exhaust flanges a wile back, but on his web-site he put a link to somebody who wanted to take over making them, or make down tubes for them. I sent an E-mail.


On the subject of new exhaust and headers; I know there aren't big power gains from aftermarket headers, but I'm wondering what size exhaust pipe would you use on a L20? 

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Depends on the cam, porting, carbs, etc. I always ran a 2.5" exhaust with either a turbo muffler or a more expensive and less restrictive Borla "lazy S" muffler. Race cars got a straight through Borla.


Hell, I run a 2" exhaust on my 1275cc Sprite.

Edited by Stoffregen Motorsports
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  • 2 weeks later...
On 10/19/2020 at 11:48 AM, banzai510(hainz) said:



Sure do wish Hainz would do videos on the KA, VG and VQ engines.  His L motor videos wereand are very helpful.  Thankyou for putting them out forall of us to benifit from.

Edited by Charlie69
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