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'73 620 - Keeping it running, but still having fun


G-Duax

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My name is Gordon, and have had a few Datsuns over the years, 510s, a 411, a 311, a 521, and now my 620 rat. Been on this forum getting free info for quite a few years, figured I need to post up a little what I've done, doing, and will be doing on this '73.

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First off, I bought it about 10 years ago for $500, barely running, and banged up pretty bad.

The guy I bought it from used it for 4-wheeling, It had a body/bed lift kit in it, and 2" lift blocks on the rear springs.

The early years it sat, and I did little things, like replacing the front fenders, a new front bumper, a good used grill, an H4 light conversion, getting rid of the 2" blocks under the sheet metal, adding a scirocco radiator, electric fuel pump, new windshiel gasket, a pair of chinese 'tuner' seats, and attempted to have the brakes fixed (nightmare).

 

Supplied all the parts master & wheel cylinders, shoes, brake lines to a 'buddy' with a shop in exchange for a vintage kart engine he wanted.

Unfortunately, he let one of his emplyees do the work, that also owned a 620.

I think half the parts went on the other guys truck, as after getting it home, I found fluid running out of the front cylinders.

I eventually got the engine back from him, but I was so pissed, I didn't do a thing to the truck for a few years.

 

Two years ago, I started working on it again.

It got all new brake parts again, a gear reduction starter, with seperate relay, a PowerMaster mini 70 amp, 1-wire alternator. For wheels, it got a set of Decem-10, 15x8 rims out of Japan (weigh 15 pounds each), and Radial TAs, a Addco front sway bar, turning the 2" riser blocks on the front, to 2" lowering blocks, backing down the torsion bars to drop the front a little, and a set of Bilstein shocks. Then all new tie rods to take all the jitters out of trying to go in a strait line down the freeway.

 

The engine was replaced by someone with an L18, with a Weber DGV, and mystery header, into a fairly ratty 2-1/2 tail pipe, and some small turbo muffler. It ran faily well, considering it only had 100 psi compression, so the engine was put on the back burner.

About a year ago, it started loosing coolant, and running like kaka, so I popped the head thinking I blew the gasket. Gasket was fine, but hound that the epoxy patch some moron put over a crack from the #4 exhaust port, into the water jacket had failed.

 

So I went to my spare parts stash (one whole bedroom in my home), grabbed a head, a 264 degree cam, and a set of Schnider springs & retainers, ground on the ports a little, and put it back together.

It was then I found the rust pitting in the cylinders, which would explain the low compression. No matter, it would still run 100 mph, so I just went back to driving the dog snot out of it.

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About 4 months ago, the clutch started slipping, so I dropped the trans, and installed an OS Giken twin plate, all metal clutch & 7 lb flywheel.

While I was in it, I rebuilt the 71B 5-speed, and addressed the 2 false neutrals it had next to 5th & reverse. That was due to the little cross pin that retains the internal sellector rod. The pin, it's hole, and the slot in the selector rod was all worn, allowing the lever to go too far to the right. Fitted an oversize hardened die ejector pin (from McMaster-Carr), reaming the holes to fit, then hand fitting the slot in the rod to just get enough travel to get into those gears.

The clutch took a little getting used to, but not much worse than any cycle I've ever rode.

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Then about a month ago, the engine started giving up, missing at idle on #2 cylinder, and just didn't have quickness it had before. A quick compression check showed 85#, 0 (zero)#, 85#, and 65#.

 

Dang, wish now I hadn't put off building a new engine all these years........

Oh well, grabed another L18 core I had in the back of the house, tore it down, sent the block off to be fitted for an odd-ball set of 88mm JE pistons. I say odd-ball because they have very high pin heights.

No idea what they were built for, but also in my spare room were a set of FJ20 turbo rods, that are 140mm length. Had to make a new set of pin bushings (21mm vs, 22mm of the FJ), and the piston domes will need to be cut back 1mm, and new valve pockets cut.

That will leave a 1mm dish, and with a Nismo 1.5mm head gasket, will leave me at 9.75-ish compression ratio. I may go to a 1mm to bump that up a tad, not sure yet.

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Block should be back next week, I'll post a few pictures as the engine goes together.

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Small update,

I finally found the correct speedo drive gear so that the Z-car 71B trans with my 4.37 rear gear gives me a true speed on the dash.

 

22 tooth 'Orange' gear & holder.

Found it at a shop in Japan that specializes in the early 5-speeds.

 

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No progress on the engine, as the machine shop that the block is at is saying 2-3 days before it's done.

That is also holding up making a windage tray, crank scraper, and extending the sump.

 

Did go to start cutting into a Z-car air filter housing that was planed to fit my quad bike carbs, but I was assuming too much.

With the SK manifold, and carbs, I run out of room to the brake booster, by about 1/4".

Had to decide to either dump the booster, or just run some other filter set-up.

Ended up trading the SK manifold, for a very short Mikuni (3" long).

This solved the air filter clearance issue.

Had to add 1/2" spacers under the carb mounts so the filter cleared the distributor.

Also made filter mounts to support the weight of the Z-car filter housing.

 

Note the grey finish on the manifold.

This is ceramic coating, to keep some of the exhaust system heat out of it.

 

The carb bowls will also get coated.

 

DSC07958.jpg

 

Carbs are from Vance & Hines, Mikuni VM38s.

Custom made smooth bores, that were on Terry Hines 1980 record setting bike.

(you can find strange things on eBay)

VanceampHinesConeHeadcarbs.jpg

 

Old SK manifold, swapped for short Mikuni.

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I need a 22 tooth for my 4.11 swap. Nissan dealers were less than helpful. I mean it you come out worse than when you went in. How much was it??????

 

Those were used on the 720s under the 32702-58S22 number. Probably used on the 4.375 axle Cab.Chassis option. Orange = 22 tooth... did not know this till now... thanks.

 

Purple is 21

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You will cry, it was 3000 Yen, but I have close to $75 into it by the time all the agent fees & shipping were added in.

 

Here is the info I've found on all the gears, many are not available any longer:

 

  Nissan Pt #     #T   Color    Ratio   Gears

 
  32703-78100   16T (yellow)  3.364   37/11
  32703-78101   17T (black)    3.545   39/11
  32703-78102   18T (blue)     3.700   37/10
  32703-78103   19T (white)   3.900   39/10
  32703-78104   20T (red)      4.111    37/9
  32703-86401   21T (purple)  4.375   35/8
  32703-86402   22T (orange) 4.625   37/8  (32703-P2622)
  32703-86403   23T (green)   4.875   39/8
 
  32707-7800 16-19t Sleeve Assy
  3270766300 20-23t Sleeve Assy  (
 
The 20-23T sleeve PN (32707-66300) has an alternate 32707-P3620 or 32707-C8301
 
22 & 23t gears - 32703-86402 or 32703-86403. (gear only)
32702-52L21  is assembly (22t)
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The 20-23T sleeve PN (32707-66300) is very common, so I probably have one.

 

22 gears - 32703-86402 I don't have. It also has to work in a later post '80s 71B case. 

 

 

My failed attempt to make a 22 tooth out of two 11 tooth sections and JB weld. The sleeve was wrong. Needed to hold the larger diameter several mm away from the worm gear. It drove about one car length and started to move the speedo... then crushed it. Had to go back to the 20 tooth.

 

Mikes%20speedo%20pinion%20change%20003.j

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  • 2 weeks later...

Dang, no progress :blush:

Machine shop still isn't done with my block & rods......

 

So I made this up so that it will be easier to ballance my rods:

 

DSC07729.jpg

 

Just waiting for the little digital scale to hit the door.

 

For years I used to hang one end from a spring, and rest the other end on an Ohaus scale, but it's a paln.

People on line wanted $200 for one of these jigs. This was built with just old scrap from around the shop.

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Finally got the block back (but not the rods yet :( )

 

Went through, chased all the threads, installed new frost plugs, and drilled/tapped the oil gallery plugs at both ends.

 

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I see a lot of mis-information on doing the gallery plugs.

The correct way is to drill the holes for the 3/8" NPT tap, which needs to be drilled 9/16", and at least 1" deep (to clear the lead part of the tap).

Then tap the hole, stopping every once in a while to check how far your plug goes in.

Pipe threads have a very wide tollerance, so taping them to get the plugs you have to the correct depth is important.

A standard allen head plug when tightened in to just below the surface, will not reach the intersecting gallery holes.

Do I need to say, that you have to be damn sure you get all the shavings out ?

Once everything is clean, use a dab of your favorite sealer, and install the plugs.

 

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Also note the the timing chain squirter is missing. Not only was it half worn through, as most of them are, but the machine shop that did the block were less than easy on it when they pulled it with a pair of pliers. Waiting for a replacement :), or I will have to machine one.

 

Edit: Fould the oil squirters in Japan. I brought sveral in, and have extras listed on eBay.

 

My cylinder walls, after fitting the JE pistons, are only about .080" thick.

Even though the machine shop assured me that they would be fine, seeing I am not boosting, and my bore size, I decided to do a partial fill with Moroso block filler. So right now, I am soaking the water jackets with vinegar, getting all the lose rust scale out.

As soon as that is done, and the acid is neutralized (water/baking soda solution), the block is dried with alcohol, I'll do the filler.

Oh yeah, officially this is a completely stock L16, I wouldn't lie.........

 

 

Decided to go H-beam rods, since they were way lighter than the turbo FJ20 rods.

Wrist pins are 67 gram Wiseco units. (about half the weight of stock)

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  • 2 weeks later...

Finally got my hands on a late L6 spray bar.

Soon as it was in my shop, it was cut down to the L4.

Of course, it needs to be used with 4 of the L6 cam towers.

 

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All that is needed to connect the 2 halves is a short length of fuel injection hose, and a pair of double layer spring clamps (from a Toyota fuel system).

 

While waiting for the machine shop to hone my rod bushings to size, I did do a little more work on the block.

Finished the hot vinegar pickeling of the water jackets. It took about 3 days.

It outer surface was washed down one more time with brake cleaner, primed & painted with VHT (cast iron color), then baked via a tent, and a high watt heat gun for 2 days.

 

Then removed the oil filter bypass assembly, and machined a solid plug for it.

 

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I bottom tapped the main bolt holes, and picked up a set of longer (80mm) 12.9 SHCS, to add a little more strength to the lower end.

My son's will get ARP studs, but he's aiming at turning his close to 10k, I'll be staying under 8.5.

 

It has the crank sitting in bearings now, waiting for the damn rods !!

When I can finally get them, I will start on the pattern for the crank scraper.

 

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I also located a set of the turbo L6 head bolts over in Japan, they should be here a week from now.

The oil jet for the timing chain just left US customs Friday, so they should be here by Tuesday.

 

Oh, I changed brands of block filler. Found out the the Moroso stuff won't work with anti-freeze, and tends to distort cylinders while it sets up.

Went with Hard Blok brand instead, which can be used with anti-freeze, and hardly moves at all while setting up.

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Dang, no progress :blush:

Machine shop still isn't done with my block & rods......

 

So I made this up so that it will be easier to ballance my rods:

 

DSC07729.jpg

 

Just waiting for the little digital scale to hit the door.

 

For years I used to hang one end from a spring, and rest the other end on an Ohaus scale, but it's a paln.

People on line wanted $200 for one of these jigs. This was built with just old scrap from around the shop.

 

I made something similar but couldn't get the weights to read the same each time. It wasn't repeatable. The scale was maybe too sensitive. It was from our materials testing lab and the electric fan in the room pushed on it enough to affect it's readings. Take two readings on a rod and they were never the exact same maybe +- a couple of grams (.07 ounces) Figured I could get them closer than that so I left them. Maybe go back some time with a better method. How close should they be???

 

Was able to get the pistons better than 1/10 of a gram between all 4. That's 0.0035 ounces.   

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This $10 scale only reads down to a 1/10 gram, and I only try to get within a spread of +/- 1/2 a gram.

When I did engines in the past, it was with the old string & ballance beam scale method, and never had a repeat problem.

Some times having friction in the set-up will cause issues.

This set-up has a couple of sealed ball bearings in the big end centering pilot, and the small end pilot runs on a polished bolt.

I'll see how it works when ever I get the rods back.......

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Edit for repeat content.  

You may want to hit your local hardware store for a small bearing that fits in the small rod end.  I don't think you'll like how your scale works.  I just threw one of those away that came with my new espresso grinder.  .5 gram accuracy, +/- 2 grams.  No good.  

 

With all the work required to repair old rods, you can but a set of custom aftermarket rods for about $100 each, that are bushed, straightened, balanced, sized, shot peened, and have ARP quality hardware, plus they are MUCH lighter.  Molner.  

 

You can build a little sheetmetal ramp and use some clay to get a bit more block filler into the block and still allow for really good water pump flow.  Mix it extra runny or it really difficult to get it in through the top of the block when you're topping it off.  Continually stir it, as the bigger solids tend to drop out.  You barely need 1 bag (1/2 bucket).  You may find that the spray bar is unnecessary.  The guy who holds the 240Z land speed record doesn't use one either, provided your cam has a good heat treat.  Yours looks reground without a heat treat, so you may want to send it out.  Necessary insurance with these soft cores.  If you think its not super soft, tell me how they drilled the internal lobe oiling.  They're MUSH.  The spray bar is a band-aid to try to overcome improper hardening, or for use if you had to weld the lobes and you lose internal oiling.  

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This scale is +/- 1/10th, and I have checked it by reweighing the same part mutiple times, with some other part being weighted in between each try, and it repeats to the 1/10th every time.

 

The small end, running on a polished bolt rolls easier then the big end, which as ball bearings on it, so no problem there.

 

I could have bought a set of 140mm H beam rods for under $300, but I chose to go with the FJ turbo rod, that stands up to 50psi boost, as it came from Nissan. That's why, I didn't even bother having them shot peined, as they are over-kill as it is. All I did was make smaller ID wrist pin bushings, and polish the beams to remove the forge parting lines..

Cost: $50 for the rods, $25 for the stick of phospher bronze, and what ever the machine shop is going to nail me to hone the bushings to size. Unlike the L-series rods, these came with 10mm rod bolts, not 8mm.

 

And that cam is not a regrind, as it has the stock base circle diameter. 20 years ago, the Japanese aftermarket was putting out really high quality products for the L-series engines.

 

The spray bar also helps carry heat away from the springs. Many people don't realize that oil flow to the head helps cool the head.

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The spray bar also helps carry heat away from the springs. Many people don't realize that oil flow to the head helps cool the head.

...until the oil is heat saturated, which typically doesn't take long.  The Aluminum head will remove more heat than the oil, once its up to temp.  And the cam provides plenty of oil to the rockers and springs as-is.  Dave Rebello rarely adds the extra oiling unless you plan to endurance race.  

Of course I won't have my engine running longer than 5 minute at a crack, so no worries on my end.  You'll apply a different type of punishment to yours.   :thumbup:

 

How much do those rods weigh?  I think mine came in at 534 grams.  I paid $10 each to get my bushings honed.  

 

And you have a brand new Japanese aftermarket cam that's never been run???  I thought it was difficult to find an unground aftermarket blank.  Your's is even more rare!  

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You did get the old doubt meter going though, on those FJ rods having a lot more mass than what I really need.

I just pulled a stock one out of storage, and it's over 800 grams........

 

I've been importing parts out of Japan since 2001, and that long ago, there was a lot more of this stuff floating around,

like the OS twin cam heads, titanium rods. Wish I had grabbed more of the stuff.

Right now there is a single L4 cam listed in Japan, and the guy wants $600 for it.

This cam was from back then. We also have a blank :)

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Well, thanks for Ibrooks6174 supplying a stock 620 pan, so I didn't have to wait until I pulled the still running engine out of my truck, I got to work chopping it, and a deep sump Hemi pan up, and starting my deep sump 620 pan project. It will hold about 2 more quarts.

 

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Once I manage to weld these two parts together, I'll extend the original windage tray, and maybe add a few additional baffels.

 

Gave up on waiting for the machine shop to hone the new bushings in the FJ turbo rods, and ordered some H-beam FJ20 rods.

They will be here Monday, and I can then start making new bushings for them.

Only this time I'll either find a shop a little more on the ball to get them finished honed, or I'll just buy an industrial pin hone.

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Almost finished with the pan.

Just needs some prep, and paint at this point.

 

During construction:

 

The baffle / windage tray.

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Extending the pick up tube (2.63").

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Flared intake end of tube (flare cuts down on cavitation at high rpm).

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Strainer is off a Toyota 7M engine, had more screen area.

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And finished pan before paint.

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I will probably start on the scraper next, as the new H-beams are in.

Being 140mm length, they weigh in at 552 grams, but that is still 80 grams lighter than the factory FJ turbo rods.

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It will if I do a remote relief valve as I am doing on my Toyota.

Stock 'in the pump' relief valves generate a lot of heat.

Simple hydraulic tech, any oil that is pressurized, then released, without doing work, turns the power used to pressurize it directly into heat. (learned that 35 years ago, first simester of a fluid power degree).

By doing a remote, and plugging the stock relief, oil is routed out to a cooler, and then back to the pan.

So at 8k, the pump is flowing 4 times the oil than it does at 2K.

Engine gets cooler oil.

Also, aftermarket relief valves are adjustable, just turn the screw.  :)

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