Measurements for an SD22 Flywheel

[620slodat]

First, I need to say that this is as much for helping me keep track of what I have as giving the information for somebody else to use. I used a Stanley tape measure, so the measurements are not in decimal inches.

 

The outside diameter of the flywheel from outside of tooth to outside of tooth. 11 15/16ths minus (in other words, not quite 15/16ths).

The outside diameter of the pressure plate face. 11 3/8ths minus.

The inner diameter of the pressure plate face is 5 7/8ths minus. 

The center to center dimension of the mounting bolts to the crank shaft, and 6 bolts total. 3 11/16ths minus.

The mounting bolts are 7/16ths minus, probably 10 mm.

The center hole is 2 7/16ths (minus maybe? It's hard to measure these small items).  

The weight of the flywheel is 25.6 lbs. My scales wouldn't weigh the flywheel, so I had to weigh myself while holding the flywheel, then just myself alone, and 25.6 lbs is the difference.

The flywheel has 199 teeth. I counted them twice to make sure, and came up with the same number each time.

 

I'm not a metric whiz, but I did work with measurements, and fractions, every day of work. So, I'm pretty confidant that these dimensions are accurate.

 

Does anybody recognize these dimensions? I know they correspond to something, maybe the L series. I'm not real good yet with the differences between the series. I'm primarily learning about the 620 and early 720 pickups.

 

Don

 

 

[datzenmike]

57 minutes ago, 620slodat said:

 

The outside diameter of the pressure plate face. 11 3/8ths minus. 

 

This comes to 288mm so I'm not seeing this. The SD22 used a 225mm clutch disc so the PP face that contacts it should be roughly the same. Even the 300zx turbo only uses 240mm clutch.

 

 

57 minutes ago, 620slodat said:

The weight of the flywheel is 25.6 lbs. My scales wouldn't weigh the flywheel, so I had to weigh myself while holding the flywheel, then just myself alone, and 25.6 lbs is the difference.

 

I've measured several L and Z flywheels and they are either 29 or 21 pounds (give or take) depending on engine size, 4 or 6 cylinder and vehicle weight. It's very possible the SD is 25.6 pounds. The engine side is usually scalloped on the lighter ones.  

 

 

 

 

The SD22 uses the same transmission type so the starter ring must be the same, same 225mm pressure plate so the mounting bolt pattern is the same, same 6 bolt mount to crankshaft.... I don't see why Nissan would make it different in any other way from the gas engines. I have a SD25 225mm flywheel mixed in with about 6 or seven others. I assumed they were compatible and there was nothing obviously different to my eye. The SD22 and SD25 flywheel part numbers are unique to those engines but this does not mean they won't fit on an L , Z, CA or KA series engine.

[wayno]

I had a Z24 pressure plate modified to fit my SD25 engine, they changed the six mount holes to where they looked like uni-lug rims, and they put a SD22 ring gear on the Z24 flywheel so the starter would work as the ring gears are different, they told me it would work fine, to this day I have never mounted it to an engine, it will except a 240mm disc/clutch cover.

[datzenmike]

Never thought of the ring gear wayno. I checked L20B/Z20/Z22/Z24 are the same ring. The SD is a totally different number.

 

So I'd better look at all my 225mm flywheels and try to find that SD25 one that's mixed in.

 

All 720 Z20 and Z24 were 240mm flywheels.

[620slodat]

10 hours ago, datzenmike said:

 

This comes to 288mm so I'm not seeing this. The SD22 used a 225mm clutch disc so the PP face that contacts it should be roughly the same. Even the 300zx turbo only uses 240mm clutch.

I've measured several L and Z flywheels and they are either 29 or 21 pounds (give or take) depending on engine size, 4 or 6 cylinder and vehicle weight. It's very possible the SD is 25.6 pounds. The engine side is usually scalloped on the lighter ones.  

The SD22 uses the same transmission type so the starter ring must be the same, same 225mm pressure plate so the mounting bolt pattern is the same, same 6 bolt mount to crankshaft.... I don't see why Nissan would make it different in any other way from the gas engines. I have a SD25 225mm flywheel mixed in with about 6 or seven others. I assumed they were compatible and there was nothing obviously different to my eye. The SD22 and SD25 flywheel part numbers are unique to those engines but this does not mean they won't fit on an L , Z, CA or KA series engine.

 

 

Thank you for replying DM and wayno. It is a big help to me to understand how the measurements were taken by the engineers. 

 

One thing I was wondering about was how the engineers did their measuring, and now I know. The disc is one size, and the pressure plate mounting surface adds to that size. I happened to think last night that I had the new clutch pressure plate and disc here, so I measured them this morning. The PP measures 11 3/8ths minus overall diameter with the mounting surface included, and 8 15/16ths overall for the contact surface. I happened to think that my computer should change inches to metric, so I tried. It seems to work! Anyhow, 8 15/16ths  is 227mm, so DM you are correct in that the SD22 is a 225mm DISC. But, the pressure plate mounting surface needs to be accounted for also. This should take the flywheel, with teeth, out to about 11 15/16ths.

 

I have had the flywheel surfaced,(the old clutch disc was badly stuck to the flywheel), so the flywheel was probably about 26 lbs originally (maybe only about 81K miles on the motor). I know that flywheels can vary in weight, even among motors of the same type. This was why I included the weight. This brings up a question that I was wondering about. Is the motor internally balanced, or externally balanced? I was wondering about the flywheel as it seems to be about the same all the way around it. I'm guessing that the motor is internally balanced. 

 

I know that the transmissions can be used among many different motor families, with a change of the transmission front housing to the SD22 housing (starter motor mounting is different). Consequently the flywheels dimensions had to have been the same among the different motor families. This information confirms to me that the flywheels are the same. Only change is the weight.

 

Don

[wayno]

The SD22 flywheel has a totally different mount pattern than the SD25 flywheel, they are not interchangeable unless the late SD22 with 5 main bearings is different, I have never seen a 5 main bearing SD22 so I don't know about them.

SD25 flywheels are kinda hard to find Mike, don't scrap that flywheel, but finding a buyer will also be a pain unless it's put on ebay, eventually it would sell on that place.

[datzenmike]

Confirmed the SD25 is a totally different number. I'll go out to day and sort through them and try to find it. I probably have 3 or 4 225mm wheels and at least 2 240mm. Tell the truth wayno they look identical but once picked out maybe obvious. It was a crushed vehicle upside down on a flatbed. I saw the 5 speed looked like a 71B but the starter was wrong so figured Mazda or Toyota I asked the driver (who was hauling it away in the morning) and he said he didn't care if I helped myself.  I got up there and finally saw it was a diesel and it all clicked. Had to unbolt the flywheel and PP to get the transmission out. The starter I dropped off at your truck one Canby. The front case went to PPeters for a 71B 5 speed swap into the Roadster.