U20 Run Stand Project

[mtngoat]

Geez, that's not a crazy price. Must fit forklifts too or something!

 

The stand is taking shape. Screwed it together, got the wheels on, added positions for engine and transmission mounts. Now we'll add the actual mounting point risers, then get the radiator in place. 

 

Also removed the oil pan from the block, which had pinholes all through it. Subbed in our spare from the torn apart U20. We'll see if cycling the pan gasket works. Should be OK for a run stand. It did crack on one side, we'll see how gasket maker holds up there on basically unclean surfaces.

 

Got a look at the crankcase, everything looks very clean. No burned/baked on varnishy stuff anywhere that I can tell.  

Edited December 6, 2025 by mtngoat

[mtngoat]

We took a look at the odometer for the car this engine came from. 34k it says. Which means the motor has 34k, 134k, etc. Given that the throttle shafts are super tight and taking into account the borescopes of the cylinders, I'm not seeing 100k+ of wear in there. Also, the engine number does match the one on the info plate on the car. So either it has been rebuilt, or we did in fact incredibly luck out on a low miles motor which is 60 years old, give or take. 

 

Muffler showed up, we cleaned the stock gauges and will try to use them on the instrument panel for the run stand. It's a '68, so it has the crazy combo gauge for oil, fuel, temp and ammeter. Looking at the guts it's a wonder of old school analog stuff, all shoehorned in there.

 

And of course the cable driven tach, hilarious! I'd been wondering how to cap the drive port on the distributor, then it hit me...we have the cable, why not simply use it? 

 

Looking at the insulators on the ammeter ports, I'm wondering if I should attempt a refresh or leave them alone. Poked at them a bit, they don't seem crispy or anything. 

Edited December 9, 2025 by mtngoat

[mtngoat]

We've finally advanced to getting the engine off it's build stand and onto the run stand. The rear is supported by blocks up to the flanges on either side of the oil pan. We designed them to be out of the way of the flywheel and backing plate, so the flywheel can be installed while the engine is on the run stand. Next up, the framing to support the transmission. Then on to exhaust and radiator mountings. 

 

 

Edited December 28, 2025 by mtngoat

[banzai510(hainz)]

Hope that holds

[mtngoat]

Me too! Should be OK, there's no dyno so torquing will be minimized. Once we get the transmission on and the mounting for it, it will look better, and hopefully be better. What you're seeing there is a temporary arrangement merely to get the flywheel on without it sitting on the floor or swinging from a hoist. 

 

I'll also be adding a cross brace to the engine risers to tie them together. I'm roughly copying one I saw on the 'tube, and he was running a chev 350 on a stand built from 4x4s. Looked solid when running. Hopefully. 

 

We're pretty jazzed about the lack of wear and the 34k miles that was on the odometer. Could it be true? Once we get it spinning, we'll check compression and see. 

Edited December 29, 2025 by mtngoat

[datzenmike]

3 hours ago, banzai510(hainz) said:

Hope that holds

 

You meant the oil filter, right?

[mtngoat]

good catch. yes, we'll go around it and replace stuff like the filter. right now concentrating on the stand itself. then we'll change the oil, filter, etc and maybe clean it up some too. rewiring the alternator/regulator setup is also on the to-do list, old very crispy corroded copper in there, one wire simply snapped when handled. Two others are clipped for some reason, and the remaining one is removed from the plug housing.

 

I'll also have to dig through my small parts drawer of brass fittings and see what I can come up with to pick up the stock oil pressure line and route it to the gauge panel. If not, perhaps a Z sender unit will fit the port on the block, and I can run that gauge. 

 

Not looking forwards to plumbing the radiator. Back in the day before JIT stocking at auto stores, you could simply go browse the wall 'o hoses. Now it will be more of a pain. I didn't see any of the stock hoses while sorting parts mountain, and I'm not sure i'd trust them anyway. On the other hand, it will be on the stand and seeing a leak will be pretty immediate. 

 

Once we get it running, may as well install the pertronics electronic ignition I picked up years ago. Goatlet thinks the points are cool, analog baby! This car is EMP ready if we're ever pulsed by China or whoever. Replace the points back into the system, good to go. On old rigs like this, the only transistors in the entire vehicle...are in the radio!

Edited December 29, 2025 by mtngoat

[datzenmike]

Ha ha that's just me on my crusade against fram filters. Only thing they are good for is masking the hole if you are painting the block.

[mtngoat]

We got the transmission support installed, and with that the hard part is over. Now that the engine transmission combo is mounted up, much of the rest went pretty fast. Radiator and expansion tank is installed. We found the old hoses to the radiator, the bendy one for radiator out to water pump is a little crunchy, but maybe OK. It's not like we won't see it leaking if it does. Test fitting of the muffler is done, I ordered one larger than necessary by accident. So we have an pipe expander on the way to make some adaptors. Exhaust hanger not yet installed.

 

Today we want to have some cool fun and will be building the instrument panel. 

 

We checked the oil in the transmission and it looks and smells fine. Didn't check the drain plug for metal debris yet, didn't want the mess.  We'll change it out when we do the oil change on the engine. Any preferences for gear oil, or should I just go with whatever 90W gear oil is on sale? 

Edited January 3 by mtngoat

[mtngoat]

Todays progress was entertaining, we created and installed the control panel, with both new and the stock Datsun steam gauges. Now the wiring and plumbing headaches begin. Ordered a pipe expander to make adaptors for the exhaust. We also found a NOS hose to replace the funky one! We'll see if that is any better, but it doesn't have any soft spots on it like the other one does. 

Edited January 4 by mtngoat

[mtngoat]

Did some more building this weekend. We dug up the engine bay harness, located our voltage regulator, and began piecing the electricals together. We had to redo two of the wires emerging from the alternator. Soldering old corroded copper wires sucks. Finally managed to get the solder to wick properly by sanding the wires themselves until the strands were all bright copper again. 

 

We removed all male connectors from their housings and sanded the contacts clean. At this point I realized it would be tough to keep going on the wiring without an actual drawing, so I cut and pasted this schematic together using schematics from 311.org combined with what I think needs to happen.

 

And, it helped me understand the curious operation of the 'two way' behavior (charge vs battery draw) with respect to the ammeter having the common port for the electrical system at it's positive end. With engine off, the car draws from the battery of course, and the 12V source at positive terminal yields a negative ammeter reading. With the engine running, the current is sourced by the alternator, powering the node at the positive terminal and charging the battery, yielding a positive reading then neutral as the battery reaches the nominal rail voltage. 

 

It also helped with my understanding of the ballast resistor on the ignition. Used only in 'run' position, it is bypassed for 'start' in order to supply the hottest voltage to the coil for starting. I guess the points would last longer when powered by a lower voltage for the long term when running? 

Edited February 2 by mtngoat

[docbainey]

On 12/28/2025 at 4:17 PM, mtngoat said:

We're pretty jazzed about the lack of wear and the 34k miles that was on the odometer. Could it be true? Once we get it spinning, we'll check compression and see. 

 

My experiences with the U20 are that they're pretty much used up at around 30K~40K miles. Timing chains and rod bearings.

[mtngoat]

Race miles or road miles? That sounds odd compared to my other Nissan engines. I'm not seeing the wear. Regardless, we're going to pull the tensioner on top and evaluate it and get a better look at the big guide. A look in the parts cabinet shows I had some foresight when I worked at Nissan while going to school in the early 90's and had access to cost plus 10 pricing. Upper guide, upper and lower chains, NIB!

 

When we do get it running and get to a compression test I'll be very interested in the numbers. I seem to recall 185 or better and even across the cylinders as acceptable results for a used engine, I wonder what peak numbers would be on a fresh one. 

 

Also, was doing more reading and one guy said to recheck the torques in everything on the bottom end, crank and connecting bolts. Not sure about this...do I get good torques breaking them loose to retighten them?

Edited February 4 by mtngoat

[datzenmike]

You can do a compression test if curious without it running. What ever the readings it will be higher when running. Will pre-lube the bearings too. Compression for the U20 is 9.5 so 185 would be quite good. 

 

You can loosen and tighten the bolts as many times as you want as long as they are not over tightened past their yield strength. This is highly unlikely on old engines before TTY bolts started being used in the late '80s? Use a good torque wrench. 

 

 

[banzai510(hainz)]

I like that muffler. Quiet turbo. the best

[docbainey]

The 30K~40K miles comment came from buying running cars for parts for the race car operation. The durability of the production roadster engines is nowhere near the 'L' series. 

 

Engine Timing Components 2000 - Datsun Parts

 

Datsun Competition Preparation Manual v1.1

 

Be mindful that the Prep manual was written in the late 60s. Back then they knew of the short comings of the chains, tensioners, rod bearings, rod bolts and a host of other areas that need improved for durability.

 

[mtngoat]

Good resources, thanks! I'll read up. 

[datzenmike]

 

Timing Chain Tensioner...

 

When the tensioner loses it's oil, it still has that very stiff spring holding the shoe against the chain. The L series tensioner is similar and I worked out the extra pressure exerted by oil pressure and it amounted to 8-10 pounds and this was at full oil pressure not idle and low speeds. It may slap till full oil pressure is restored if the chain is worn and in need of replacement, but no way it affects the cam timing in any way. For the timing to vary, the slack would have to be on the tension side which is impossible because...

 

The engine is constantly pulling the timing chain downward on the left side against the resistance of the cam and the valve springs and why it's called the tension side. For there to be any slack, the engine would have to be turned backwards by hand. 

[mtngoat]

We're a ways out on a run so we have time to sort that stuff out. 

 

Basic to-do list:

- finish wiring harness

- finish control panel gauges and switches

- add more cross braces to stand

- finalize exhaust and brackets

- fuel plumbing and fuel tank (7 gallon marine tank with fuel pickup, for small outboard motors)

- install battery position

- radiator -> pressure tank hose

- inspect upper tensioner

- oil change and filter

- transmixer oil change

- fix choke cable (a kink in one of the two cables, in the box shaped upper housing means cable will not 'push' into sleeve when pushing knob in, it just bends and will not push into the sleeve)

- come up with throttle cable system. Maybe the choke cable setups for a lawn tractor will work. 

- pull pan and retorque the bottom end? Includes slathering oil on journals while they're open.

- coolant fill of course. 

 

Then I had some odd ideas about a possible ghetto dyno setup, using lateral thinking. Normally a dyno presents a mechanically resistive load for the engine to turn. This involves all kinds of large, heavy, fancy load mechanisms from mechanical to electric (turn a big generator which feeds a huge resistive load). 

 

I thought hmm, maybe one could get partway there via a simpler mechanism. I wonder if a flywheel style disk could be fitted onto a splined sleeve for the trans output shaft. Then you mark this flywheel, or print up some segments/teeth which go around the rim and act as an encoder of sorts. Then you'd use an RPM meter like the one I use for model aircraft propellors to measure RPMs. At this point, the idea is to measure the rate of change when you hit the throttle. You know the mass of the flywheel and it's dimensions, you should be able to figure out the moment of inertia, and thus calculate the power necessary to accelerate the flywheel at the rate measured. This would not of course measure static power at a given output, for that you need the standard dyno system. But you might be able to come up with some useful numbers during acceleration. Just an idea. How crazy is it? 

 

I guess I'd then need to add a clutch, since just leaving it in a gear during start would probably present all kinds of problems not present if you do the same thing with the output trans shaft free of added rotational mass

 

 

 

 

 

 

Edited February 5 by mtngoat

[mtngoat]

Did some reading. The mass of the existing flywheel should work, and a hall sensor sensor somewhere. Maybe on the crank pulley? This is all just spitballing, may be stupid!

Edited February 5 by mtngoat

[docbainey]

21 hours ago, datzenmike said:

 

 but no way it affects the cam timing in any way. For the timing to vary, the slack would have to be on the tension side which is impossible because...

 

The engine is constantly pulling the timing chain downward on the left side against the resistance of the cam and the valve springs and why it's called the tension side. For there to be any slack, the engine would have to be turned backwards by hand. 

 

Death Rattle... aka I should've been listening - Datsun Roadster Forum-311s.org

 

[datzenmike]

 OK I get it now. If the engine is turning slow enough the exhaust valve closing spring pressure forces the cam forward pushing slack onto the tension side. This would happen at around  (roughly) 150 crank degrees ATDC. And it does close enough.

 

I would expect this to also happen on closing intake valves also. That would be around 230 crankshaft degrees ATDC or about 50 degrees ABDC. That would be two exhaust and two intake jumps per crankshaft revolution.

 

Well I learned something is not impossible. 

 

 

 

[wayno]

On 2/5/2026 at 11:39 AM, mtngoat said:

We're a ways out on a run so we have time to sort that stuff out. 

 

Basic to-do list:

- finish wiring harness

- finish control panel gauges and switches

- add more cross braces to stand

- finalize exhaust and brackets

- fuel plumbing and fuel tank (7 gallon marine tank with fuel pickup, for small outboard motors)

- install battery position

- radiator -> pressure tank hose

- inspect upper tensioner

- oil change and filter

- transmixer oil change

- fix choke cable (a kink in one of the two cables, in the box shaped upper housing means cable will not 'push' into sleeve when pushing knob in, it just bends and will not push into the sleeve)

- come up with throttle cable system. Maybe the choke cable setups for a lawn tractor will work. 

- pull pan and retorque the bottom end? Includes slathering oil on journals while they're open.

- coolant fill of course. 

 

Then I had some odd ideas about a possible ghetto dyno setup, using lateral thinking. Normally a dyno presents a mechanically resistive load for the engine to turn. This involves all kinds of large, heavy, fancy load mechanisms from mechanical to electric (turn a big generator which feeds a huge resistive load). 

 

I thought hmm, maybe one could get partway there via a simpler mechanism. I wonder if a flywheel style disk could be fitted onto a splined sleeve for the trans output shaft. Then you mark this flywheel, or print up some segments/teeth which go around the rim and act as an encoder of sorts. Then you'd use an RPM meter like the one I use for model aircraft propellors to measure RPMs. At this point, the idea is to measure the rate of change when you hit the throttle. You know the mass of the flywheel and it's dimensions, you should be able to figure out the moment of inertia, and thus calculate the power necessary to accelerate the flywheel at the rate measured. This would not of course measure static power at a given output, for that you need the standard dyno system. But you might be able to come up with some useful numbers during acceleration. Just an idea. How crazy is it? 

 

I guess I'd then need to add a clutch, since just leaving it in a gear during start would probably present all kinds of problems not present if you do the same thing with the output trans shaft free of added rotational mass

 

 

 

 

 

 

OK, I am only thinking about a dyno turning mass, the flywheel is mass and it is required to start the engine, there is also the clutch cover for more weight, so what if you use the flywheel/clutch cover as the mass without the clutch disc installed, when you put the transmission in it connects to nothing, but you need the transmission to install the starter or at least the front case as that plate between the engine/transmission is too flexible by itself.

So you have the mass of the flywheel/clutch cover a known weight if you weigh it with the mount bolts or just leave the clutch cover off, bare flywheel, it is balanced and I thought about this, if there is no disc can the clutch cover plate/disc, can that plate wiggle without the disc in place???

 

I built an engine stand, or maybe it is better to say Mike Klots built it to hold a VG30, and I modified it to hold a SD25 diesel engine/transmission as a test stand to start a SD25 Nissan diesel engine I bought over 10 years ago on ebay, once I got it started I made a radiator mount that rested on the ground to run it for over an hour, but I had to take the radiator off to move it, so the next day I build that into the stand, I did not use a clutch cover on the flywheel, but I needed the flywheel to start the engine, the transmission does not move at all as the only thing in the crank is the pilot shaft.

 

 

I did better later and got rid of the c-clamps holding the radiator support frame together, the radiator hoses keep the radiator from rattling around, it has an electric fan to cool the engine, it is much closer to the radiator fan clutch now, I think I could use the stock fan now, I ran it the last version for another hour.

 

Edited February 10 by wayno

[mtngoat]

Cool stuff! Good post. The more I thought about a pseudo dyno measuring RPM acceleration, I realized I'd have to estimate all the mass throughout the system...crank pulley, crank, flywheel, etc. That could get ugly fast! So i'll continue to ponder, but it's not on the schedule. 

 

Last weekend we got a lot done. We got the exhaust installed with respect to the pipes, haven't finished a bracket yet. We figured out where to place the battery, and I actually found some fat copper cable stock I knew I had somewhere (shop cleanout of packrattage paid off!) I even had four battery clamps, new! Red and black 2 gauge wire, it's pretty huge. (It was for a man lift battery at work) The cables even had ring terminals on one end already...the right size for the starter terminal!

 

We roughed out how to use the existing engine bay harness for it's alt/regulator connections, and how to tap into the harness to get to the hot wire coming to the instrument cluster and ignition switch. Then we connectorized a bunch of wires to start plugging systems together. We now have the instrument panel hot, the run switch installed, the start switch installed, the voltage meter connected, and status lights. It's pretty cool to create something and get progress!

 

You flip the master switch (with red fast kill cover), the green indicator turns on indicating system power and the voltmeter comes to life. Push the starter switch, and the yellow indicator comes on indicating start position. The wire to the starter is done, but of course will never be connected until the Big Day. We did test voltage at the solenoid end, it will initiate the starter just fine. We also tested the starter on the bench, it works. 

 

What does not work is the stock 4 instrument cluster ammeter. When wired in, we had nothing but failure on the panel. We pulled the wires, and did a check from terminal to terminal. Open circuit, when an ammeter should return zero or very low ohms. Nope. Infinite resistance...no connection. Damn. Ordered a ten buck ammeter. Connected both cables to one post to short them together and bypass the ammeter for now. 

 

We had another crazy idea after spotting capped vacuum ports on each intake runner pair. Would it be useful to have *two* vacuum gauges, one after each carb? Helpful for tuning? I dunno. I suspect the balance tube between the intake runners might keep the different paths from reading very differently unless the carbs are wildly out of sync, which is easy enough to determine anyway. However, for fine tuning the flow balance it would sure be nice if this wasn't the case. On the fence there, might be an interesting experiment, and who doesn't love more gauges on a test panel? 

 

We also implemented a simple hinge on the instrument panel so you can tilt it up from the designed 45 degree viewing angle to 90 degrees in order to access the wires behind the panel with ease. A big improvement. 

 

I decided to order an electric fuel pump so we could set up the float bowls without running the engine. I started messing with them years ago, then dropped the project half way. One float bowl has the brass float, another has a plastic float from some retrofit kit, it will take some messing around to get them back in shape. I don't want to have to try to run the engine to do this fussy work. Pump spec is 3-6 psi, which I think is about right, and I have a mechanical regulator in the parts shelf if I need one. 

 

Edited February 10 by mtngoat

[datzenmike]

On a gas engine only the flywheel would be needed for the starter ring and the transmission or the front case for starter mounting. On a diesel more mass might help the starter past the maximum point of compression when starting? 

 

 

For HP just take a trip to a dyno and get an accurate RWHP. Subtract about 17% for drive line losses and you have the engine power. It's going to be damn hard to time how long it takes to increase RPMs from say 6500 to 7000 without drive line mass slowing it down to manageable levels. Some time in the mid '70s engine HP was changed from gross to net. Gross was measured at the crankshaft usually without accessories like alternator, water pump, no pollution controls and open exhaust etc. to boost the numbers. People complained that their 320 HP engine didn't really perform like it had 320 HP as it was now hauling a car around in real world conditions. My '76 710 says 110 HP but my '78 620 says 93. 

 

The intake runner has a balance tube connecting between both carburetors so the vacuum reading would be the same.

 

For dual SUs you need this flow meter to evenly adjust the amount of air flowing through both... Mine was $50, now they are $70. Borrow one.