L20 B flywheel question

[H20doctor]

i have my engine pulled out of my truck and now have to buy a new clutch, and update the flywheel .... 1st question.. the flywheel i have in it now is a 240 z or a 260 z flywheel, i cant remember , but its lighter than the stock L20, should I leave it ? or have it lightened ? If i lighten it .. what is the best weight for my Mild over bored block..? Or should I leave it the way it is...

 

2nd question... what is the best clutch for a L20 New.. and where is a good place to get one online ? thanks

[datzenmike]

It's lighter because the L24 motor has a larger rotating mass and doesn't need a 'heavy' one. It's likely around 21 lb. Fine the way it is and a slight improvement over stock. You can turn them down but this is more for racing and a disadvantage for a stop and go DD. 15 lb is as light as you would realistically want to go.

 

The 620/720 2wd truck clutch is the same rating as the 240/260.

[620racer]

truck flywheel is heavy almost 30#'s and 240mm large

z wheel better and closer to 20#'s 225mm. should be able to lighten to 11 or 12 #'s

[datzenmike]

truck flywheel is heavy almost 30#'s and 240mm large

z wheel better and closer to 20#'s 225mm. should be able to lighten to 11 or 12 #'s

 

 

 

 

All the 620s (L18 and up) and most 720s are 225mm. I pulled a 240mm from a 720 4x4 but I think they are only on the Z20 and Z24 motors after '82.

[HRH]

Just remember a Z24 flywheel on an L20 or vice versa will not work. They'll vibrate like a sonofabitch. Joe did that once with one of the motors they built. Z24 and KA are their own flywheels.

[DanielC]

Here is a question for Datzenmike,

I have a JDM L-18. It has a 6 bolt crankshaft. Will the 240 MM 620 flywheel fit?

[datzenmike]

If it's 6 bolt, the 240mm should fit. This would allow the use of the 300zx turbo pressure plate rated at 600 Kg pressure. The one I have is heavy at 28 lb or so. It could be turned down 10 lbs because the pressure plate is larger and heavier anyway.

 

I'm not aware that the Z24 wheels are balanced on the cranks. If they were the bolt pattern would be staggered so the flywheel only goes on in one position to preserve the balance if it was removed. Also if the flywheel were replaced the whole assembly would have to be balanced over again. Pretty sure the wheels are simply balanced like a tire and put on.

[HRH]

Yes, they are balanced as a separate unit, but something about the harmonics of the Z24/KA flywheel when mated to an L16/18/20/22 just doesn't work. Apparently it vibrated nastily, they got a L20B flywheel and swapped out, never had any more problems.

[datzenmike]

Pretty sure the L and Z are fine. I think some KA wheels have a 'nub' that only allows it to mount in one position.

 

You can see something at 3:00 on my KA crank? The wheel didn't come with it. Maybe it was a KA wheel on an L???

 

[HRH]

It's possible, but I remember the story as being it was on Todd's 2.2 motor and they threw a flywheel on, had vibration issues and yanked it off to find it was a Z24 flywheel. That's the story, but it was a while ago, possible that it was out of balance or something. I don't know. I think the clutch is bigger on the Z24/KA though, which is another reason to keep them separate. May not fit in earlier smaller L bellhousings.

[datzenmike]

Z24s were likely to be 240mm. A larger clutch would bear this out too.

 

I checked and the 240sx KA had a crank dowel. It's not clear if it might have been pressed into the flywheel and fit into a corresponding hole in the end of the crank between the bolt holes. Anyway I took a better picture of it and it looks like a tiny brass thing not in the D21 KA24Es...

 

[H20doctor]

ok i will keep the the flywheel the way it is and not lighten it any.... thanks for the help .. i do appreciate it