'77 620 advanced a tooth? Confirmation needed, please.

[Chzyrider]

Hi all, new here to this site and new to Datsuns, but not new to wrenchin' on my own cars. I could use a little assistance with some Datsun expertise and confirmation on what I've been able to research before further digging into this truck. I'm working on a friend's recently purchased 1977 Datsun 620 pickup with L20 engine that had been stripped, cannibalized and monkey-rigged by the previous owner(s) so I have no idea what has or has not been done to it other than screwing it up.

 

This is either a challenging repair project or a nightmare, I'm not sure which yet.

 

Here's the story... please bear with me.

A couple months ago I had went with my friend to look at buying this truck and there were two knuckleheads that reminded me of the tv characters 'Darrel and his other brother Darrel' messing with the carb and fuel pump trying to get it going. I was surprised they didn't blow themselves up while I was there. Well, a week or so later my friend tells me that he bought the truck. It was apparently barely running enough at the time to drive it home. He tried a little more oblivious fiddling with the carb (attempting to reduce the high idle speed and the clouds of exhaust smoke), then it wasn't running at all when he calls me shortly afterwards to tow it over to my place to help him figure it out.

 

First, I see the choke and anti-dieseling solenoid power wires were disconnected without any dangling power source seen to reconnect them. And there were a few open vacuum leaks from the missing air cleaner housing and most all other emissions parts. We removed the remaining EGR bypass body and made a block-off plate for the intake manifold reusing the old gasket (as I found that this gasket is only available by dealership special order or in full rebuilt sets). I started to rebuild the carb and discover missing springs and a lot of grey/white powdery stuff inside it....hmm.

 

So my friend found a '76 replacement carb, but it's a slightly different model of the Hitachi. The old carb only had a flat plate with a spring behind it where the BCDD would be and the replacement carb has a BCDD that does not have a vacuum or solenoid connection. So anyway, I rebuild that carb with new gaskets and set all the bench adjustments according the books. I'm still not positive which exact version of carb this truck is suppose to have with Hitachi's lack of hard-stamped ID numbers.

 

Old carb

 

Replacement carb

 

We put the replacement carb on and try to start it but it would act flooded with the occasional 1-2 second start-up then dying again. I inspected the spark plugs and they were blackened, and wet from fuel. We cleaned them and tried again but same thing and I checked for spark at cyl. No.1 and saw a weak spark, but it also has a weak battery. So we wait for another day as it charges again and we both have time to work on it.

Meanwhile, I had cleaned the rusted connections at the coil and discover the frayed fusible link off the pos. battery cable had been poorly bypassed so I replaced that. Then I manually inspected the timing and I discover the point gap was about twice what it calls for. After rotating the engine to TDC with a chain-wrench, I see the rotor is pointing ahead of No.1 position relative to the cap.

 

Close enough to be called TDC for this purpose, +/- a degree or so.

 

This image shows the rotor position at TDC ahead of the No.1 location (yellow dot). Through a couple computer programs, it measures to be approximately 16 degrees ahead of the yellow dot in the image.

 

In my online research for carb info, I recalled seeing images of the oil pump shaft positioning with the tab offset frontward at 11:25 position.

 

So I lifted the distributor out and took a photo to see if it was pointing where it should be relative to these other images. This is the shaft position on this truck at TDC. I did not remove the lower housing with the two bolts seen here.

 

With a little photoshop blending and marking the lines where the tab is, I now had an overlayed comparison image. I used another program to calculate the angle of difference and discover that the shaft tab (RED lines) is appaearing to be approximately 14 degrees ahead of the clean example (GREEN lines) that is supposed show where the shaft is to be aligned.

 

Blended image showing difference in shaft position at TDC. Yellow is centerline between bolt holes.

 

The relative comparison of these images makes me suspect that whomever previously worked on this truck had put the shaft in 1 tooth advanced therefore why it ran like crap when it did. Can anyone confirm this timing issue before I pull the oil pump and move it over a tooth for a 'try-it-n-see' thing?

 

I also found a small mention in my research that the Datsun timing sets allow for 4 degree adjustments... Can someone explain the 3 positions mentioned? Being unfamiliar with Datsuns, a wild thought is perhaps the previous owner was trying to make up for a worn chain/gear set and overshot the correction?

 

Also, other than one hand drawn diagram found online for California models, I've had a hard time determining which vacuum lead is supposed to go to the vac advance diaphram on the the distributor. Since this thing was so messed up and cannot be sure of being correct to being with, I have no real reference for what hose goes where to determine correct vacuum routing. I'm suspecting it's the front one of the two coming off the passenger side base.

 

Old carb before removal. Note the open vac on EGR passage and monkey-rigged throttle return spring.

 

Any assistance, hint, tips, or other helpful information would be greatly appreciated to get this truck running again and out of my garage so my friend can drive to/from work again and I can get back to other projects that I've had to put on hold for what I thought would only be a simple carb repair. We'll be working on it again in a few days as schedules allow and hoping for some replies here before we do.

 

Thanks!

[Laecaon]

Pull valve cover off.

 

Set crank to TDC

 

Cam lobes should look like this, if not do one more revolution of the crank:

 

Finally look through the cam sprocket for the timing mark. Should look like this:

[Chzyrider]

Thanks for the reply Laecaon, I appreciate the photos showing the cam positioning at No.1 TDC and the alignment notch. I'll take a look that way and report what I find.

Since I cannot identify if it's the original engine in it, I'm realizing that getting this truck running properly again may be quite a chore. I'm more accustomed to working on older American muscle cars & motorcycles. Other than rebuilding one Toyota 22RE engine (which the distributor does allow for putting it into the correct tooth from the top), I'm not very familiar with the foreign engines and will truly appreciate all the help I can get on this one as I'm finding out that this engine is a bit more difficult to just move it over a tooth to correct it if put in wrong by a previous owner.

[moparvwfreak]

A tooth off would cause a problem with it not running smooth. I had the same issue when I put my 78 L20 in my 73. With a little tweaking and fixing said vac leaks it should work its self out. Also it's common to need a second spring on the throttle, mine needed one because the factory spring was weak.

[datzenmike]

TDC compression on #1 cylinder (cam lobes at 10 and 2 o'clock, bothe valves closed) the notch in the back of the cam sprocket must be just below the etch line in the cam thrust plate or just slightly to the right. Here's a slightly better picture...

 

 

No matter how stretched the chain or what tooth it is on THIS is the proper position for the cam relative to the crank. If you cant adjust to this position the timing set must be replaced.

 

 

The distributor can be on any tooth as long as the timing can be set. If you run out of adjustment room then yes, It may have to be adjusted.

[banzai510(hainz)]

on the TDC spindal set up

using a screw driver the tang shoulf be on the right of the top hole and left on the bottom. Thats what I get from the 11.28 position.

 

there is a 8mm bolt upside down on the distributor where you can adjust the timming plate to more your likeing.

save this

dizzy install

 

the whole vid

[Chzyrider]

A tooth off would cause a problem with it not running smooth. I had the same issue when I put my 78 L20 in my 73. With a little tweaking and fixing said vac leaks it should work its self out. Also it's common to need a second spring on the throttle, mine needed one because the factory spring was weak.

Moparvwfeak, I never heard it running. I am told that it was running a very fast idle, when it was. The old setup was missing the accelerator pump spring, the stock throttle return spring and bracket when he got it so I fabricated a bracket and used the spring that luckily came with the replacement carb. That and the accelerator pump lever spring seem to provide enough return strength at this time.

[Chzyrider]

Here's a slightly better picture... No matter how stretched the chain or what tooth it is on THIS is the proper position for the cam relative to the crank. If you cant adjust to this position the timing set must be replaced. The distributor can be on any tooth as long as the timing can be set. If you run out of adjustment room then yes, It may have to be adjusted.

Datzenmike, Thank you for the photo! That shows a different style of number stamping than the other photo provided. Yours shows number 1 being visible at the top while the other shows what looks like number 2 at the top with a 3 visible on the outer ring. I will see what number is visible and where the notch alignment is on this one.

And, I was not able to simply rotate the distributor over counterclockwise enough to align the rotor where it should be. The vac advance diaphram will start to hit the upper radiator hose if turned any further.

[Chzyrider]

there is a 8mm bolt upside down on the distributor where you can adjust the timming plate to more your likeing.

Banzai510, Thanks for the videos! That really helps a lot!! I have already tried that 8mm bolt to slide the plate over but it's already slid over at it's extent in the direction I would need. I caught one possibility mentioned in the video that strengthens a suspicion that this may also have a mis-matched setup. If the previous owners did the junkyard switch-n-swap, it may be a total mess to figure out. The vac advance on this one points upward towards the radiator. Is that correct for the L20? Or perhaps this engine isn't what we think it is. So another question the video brings up would be if the distributor is the right one, is maybe 180 out, or if it has the wrong cap if No.1 wire can be in different positions with different caps.

 

One part he skipped over in the longer video was the factors for placing the cam sprocket at the 1,2,or 3 position, and exactly why he put it on the 2.

 

Heading out to the garage now to remove the valve cover and see what we got there.

[banzai510(hainz)]

L20s come from factory in #2 timming sprocket set up. Most others are #1

 

But mainly used for cahin strectch. long as its line up to a number you should be fine what ever number its already set to just make sure the V and dash line up. It will run.

 

Since you got a point dizzy I would put the mount on 180 oppisite so the vac adv canister is the other way.

 

But like in the photo and vid line up the spindal in the 11.28 position AT TOP DEAD CENTER !!!then drop the dizzy in the and where it locks YOU will assign that the #1 plug then go 1 3 4 2 . adjust your timming plates so its in the center.

when you start im sure it will fire off and adv the dizzy a little motre and should start running. If the carb and valve lash and you have gas.

 

 

this is EZ got go the )(zero mark) correct just pull the oil pump out and line up the DOTs on pump and spindal then insert and make sure its 11/28 then install the dizzy. center timming plates and START it

[Chzyrider]

Banzai510, I didn't realize that was actually you in the video until I played it a second time... good job, thanks again.

 

Here's what I found after pulling the valve cover...

The cam sprocket is at the 1 position with the "V" just at the left (retarded) end of the notch.

 

Can I presume the timing chain is okay at this point or do I really need to pull the cover to inspect the lower gear?

Could it have been put on the wrong number if supposed to be on 2 for an L20? Or perhaps it's not an L20?

With the previous image showing the angle difference of the tab from the clean example; Could the chain be okay, but shaft still be off a tooth?

Or would the difference be more of an obvious angle from one tooth over?

 

 

Can we identify if the distributor is the right one for a '77 620 truck by the stamped numbers?

D4A4-07 6902

22100 B8001

 

The distributor plate will not align to be secured when simply reversed, the slot is nowhere near the bolt hole. And when I flip both the plate and aim the distributor in the opposite direction and center the plate slot for securing, then the rotor is nowhere near the wire locations (marked with dots) for this cap. Could it be the wrong dist cap?

 

 

Is this the correct plate for this distrubutor? I recall seeing a post or video somewhere that showed interchangabiltiy of the distributor securing plates (I can't remember for sure where anymore to find it again, they're all blending together at this point). So this makes me also suspect the possibilty of being the wrong distrubutor or wrong plate.

 

 

 

 

 

I suppose I should also ask: How can I tell for sure what engine this is if not an L20 as presumed for a 620 truck? ..just in case it was switched so I'm not chasing ghosts with the wrong engine designation.

 

Thanks again ya'll for the replies. I really appreciate it!

[moparvwfreak]

on the pass side of the block, right below cylinder 3 i think, don't have a truck off hand to look at unless i run outside, there is an area that will show engine designation. it'll say L16, L18, L20b. that'll tell ya what engine you have. not the year but model.

[datzenmike]

 

I can tell from this picture that is an L20B. See those two bolts one above the other on the top of the timing cover? just above where the distributor goes in the hole?

 

 

 

 

 

Groove on cam sprocket must be under the horizontal etch mark or just slightly to the right. This picture is the correct way to time the cam.

 

 

Now look at this one below. Is the groove in the sprocket below or to the right of the horizontal etch mark?????????

 

 

No it isn't. This would indicate some chain stretch or wear. (or cam was installed in the wrong hole on the sprocket) Nissan has three (3) holes to allow some adjustment. Yours appears to be on the #1 hole so the sprocket has to come off and be rotated to the #2 hole and this will move the sprocket ahead about 4 degrees (about 1/2 tooth) and will move the groove to the right.

 

It is absolutely imperative that the chain be wedged in such a way that the chain tensioner can not fall out before removing the cam sprocket. If it falls out you will have to tear the front off the motor to get at and fix. Find out how to do this.

 

You need something like this...

 

To prevent this....

 

 

 

 

D4A4-07 6902

22100 B8001... Sept '74 federal for L20B 4 speed. It is likely the wrong distributor but will work if you drop the oil pump and move the spindle to re-time it into range..

[Chzyrider]

on the pass side of the block, right below cylinder 3 i think, don't have a truck off hand to look at unless i run outside, there is an area that will show engine designation. it'll say L16, L18, L20b. that'll tell ya what engine you have. not the year but model.

 

I found it, thanks! It does have a stamped L20B next to a serial number. So that eliminated that suspicion. Whew! ,

[Chzyrider]

...Yours appears to be on the #1 hole so the sprocket has to come off and be rotated to the #2 hole and this will move the sprocket ahead about 4 degrees (about 1/2 tooth) and will move the groove to the right.

 

It is absolutely imperative that the chain be wedged in such a way that the chain tensioner can not fall out before removing the cam sprocket. If it falls out you will have to tear the front off the motor to get at and fix

 

D4A4-07 6902

22100 B8001... Sept '74 federal for L20B 4 speed. It is likely the wrong distributor but will work if you drop the oil pump and move the spindle to re-time it into range..

 

Aww jeez. Thanks for the bad news..haha. So apparently it was setup wrong, and mismatched. Time to get my friend over here to get his own azz greasy while I watch and tell him what steps to do. The problem is that it will probably take twice as long or more if he does the wrench turning instead of doing by myself. He's going to owe me at least a couple more cases of beer for all this now.

 

I had a suspicion that the distributor was a '74, by those numbers. I see the head has a Nissan Japan and U57 cast in the bottom edge, front passenger side. Is this the right one? Or a '74 as well? ...or something else? Is there another number somewhere to look for there? I'm wondering what else was swapped or replaced and if from appropriate year model. I also see part of a number on the intake, but it's hidden under the carb.

 

I recall seeing glimpes of drawings of those chain-wedge tools with dimensions like we could make one out of wood or something. I'll start looking for that tool and see what I can find before we dig into it further. Where's the best source to get one of those pink tools like you showed?

 

Okay now, from what I understand of the rest... after we reset the cam sprocket to the 2 position, the oil pump shaft can then be indexed into whatever drive gear tooth that will give us an alignment at No.1 on the cap. Does that sound about right?

 

Thanks again for great info!!

[Chzyrider]

Well, I couldn't find a chain wedge anywhere locally. Most every place I checked, the employee had never heard of it before. So I made one from an old unused garden stake somewhat imitating the photos of the plastic ones, and screwed in a long rod I had laying around as a handle.

 

 

I found that if I have the straight side tight and take a long prybar to gently push back the tensioner, it will give me room to insert a small screwdriver to hold that slack and the tensioner somewhat compressed while I put the wedge in place. Then pull out the screwdriver and this slack in the chain gave me the available 'wiggle-room' to fit the upper sprocket back onto in the 2 position. During one of a few times doing this exploring the options, I did had to rotate the cam slightly with a wrench to get it pop back on.

 

 

The "V" is a bit closer to where it suppose to be. The 3 position didn't seem to help it much further. So I'm figuring this likely has a worn/stretched chain, but it will have to do for now setting it on No.2 for just getting it running at this time.

 

 

I drained the oil (it needed it anyway) and removed the oil pump. I aligned the shaft marks and put it back in. The tab was closer at direct vertical, but still no cigar! So I tried again. Same thing, so I can see how if someone previously working on this without proper information or not paying attention to how it originally came out can easily make a mistake on this procedure. I then tried to move it slightly ahead of the mark about almost a tooth worth on the small shaft gear and the tab finally lined up where it should be. So this thing was apparently TWO teeth advanced.

 

I put the distributor back on with the vac advance pointing upward and the rotor points to where No.1 wire is when the body is rotated clockwise almost all the way over on both plate adjustments. I manually turned the crank close to 10-12 degrees adjusted the distributor with a multi-meter on the points.

 

I added oil & a new filter, turned the key and.... Nothing. Wha, wha, wha... :confused:

 

I had already tested power to the distributor and it was fine. I tested again and found it had way too much resistance from outside to inside on the connection. So I had to clean the rust off that screw to get a good connection and replaced the points & condenser with a new set.

 

I crossed my fingers and other available appendages, knocked three times, said praise to the Great Wrenchio - saint of internal combustion, then turned the key and...

 

Whew, it fired right up! :thumbup:

 

I checked the timing with a light and it was close enough for warming up. It was running a bit fast of course with the choke on and I let it run a while until the thermostat opened and the choke cam had dropped. Then it had a little bit of adjustment on the throttle screw but not much to lower it down below about 1200rpm or so. I had set the Fast Idle adjustment to specs on the 2nd cam step, but this adjusting screw is also keeping it running a bit fast. I have not touched the mixture screw other than to carefully check that it's one turn out. I guess we'll have to play around with it a bit as we can.

 

So here's another couple questions-

*Which adjustment on this carb would be best to lower the idle a wee bit more, presuming all bench adjustments are supposedly correct?

*Or perhaps we still missed a vacuum leak somewhere?

Again, this thing has been stripped of all emissions parts by the previous owner. Everything was removed or plugged and only one active vacuum source to the distributor connected to the front of the two ports off the carb base according to the one drawing I could find specifying this arrangement.

 

Even more fun-

It barely had brakes with a really soft pedal when towing it over to be worked on. The fluid was low so we started to bleed the system and discovered one of the springs on the left front was not hooked on one end, and that all 4 of the star-adjusters were seized. So we removed those and eventually got them unstuck with a vice, a little heat and a lot of tapping with an old seatbelt securing bolt that happened to be the correct size for the bore to push it through.

Once cleaned up, they are spinning okay, but I cannot get them to adjust up tight through the little window in the back. I need a specially bent skinny screwdriver or some other special tool I guess. My regular brake adjuster tool was too wide to fit and a regular screwdriver was not working with the leaf spring perch in the way for the rears. So I got them all adjusted as tight as I could and still able to barely slide the drums over the shoes...they spin with a very slight rubbing noise, calling that close enough for now.

In going through the sequence procedure found on this forum for all 9 bleeders, one of the two bleeders on master cylinder would not seal again. So we had to replace the brake master cylinder which the first one (Takico style) had the wrong outlet bungs on it and the lines would not screw in. We swapped for a different Napco one (both Cardone brand remans and both were in the same part 11-1172 number box) and this one fit, but then the front outlet line would not seal on that one. I added a couple thin strips of teflon tape to the connector and it finally sealed.

 

The owner drove it away last night... yeah! ...I'm doing the happy dance in my open garage bay... But..., oh yes, there just has to be a few more but(s), ...it was really low on gas, so he went to the nearest gas station and proceeded the other 5 miles or so home. He made it just a couple blocks shy from his place when it died. He called me and said it starts, but it dies when trying to go again. I suggested he change the fuel filter since we did not know the condition of the previous filter, and since it was really low on fuel, I'm suspecting that it probably sucked up some gunk. The fuel pump looks new (previous owner), so I'm not suspecting that at this time.

 

The adventure continues... It's hurry up & wait again now to see if that works when he can install the new filter and I've moved on to another awaiting project, but I may need to add to this thread as we go. We'll just have to see if the fuel filter gets him going again or what. I told him that it may likely need some fine tuning yet as I was not able to test drive it for him before he wanted to drive it away. This thing had so much stuff wrong with it that I'm just glad I was able to get it running again as it is.

 

The owner found a replacement air cleaner housing, but it's not on right now since it still needs a securing rod to clamp it down. He will get that accomplished with a threaded rod and two jam-nuts. It still does not have breather filters on either the crankcase tube or the one on the valve cover. Again, something the owner will get when he can... $$$, ya' know.

 

Thank you all for the replies, information and advice. It is greatly appreciated!!

Wrench-on!