Z24 crank

[IverDimer]

How much needs to be ground off z24 crank to fit the l20b? Or do i just take the block and crank to machinist and say "make it fit" 

 

[longrod]

It's physically and mechanically impossible, The counter weights and rod journals are on the same circumfuse plane.  It's a urban legend that it could be done. 

[Crashtd420]

40 minutes ago, longrod said:

It's physically and mechanically impossible, The counter weights and rod journals are on the same circumfuse plane.  It's a urban legend that it could be done. 

I have no details but I swear someone here just posted they did it.... I'll try to remember where I saw it

[Crashtd420]

Check this post out and I'm sure you could even message them for more....

 

 

[datzenmike]

1 hour ago, longrod said:

It's physically and mechanically impossible, The counter weights and rod journals are on the same circumfuse plane.  It's a urban legend that it could be done. 

 

It sure won't drop in as is.

 

The counterweights can be turned down on a lathe and the bottoms of the cylinder clearance ground. The Z24 crank throw is only 2mm wider per side than a Z22 crank so must be the counterweights that do not clear the block. It's been done.

 

Only reason would be to use the L20B/Z20/Z22 block but you're also reducing the deck height so piston skirts are going to experience an increase in side loading and friction.

[longrod]

your for getting about the connecting rods, there no way you can clearance the bottom of the cylinder bore enough. 

there's more reason it wont fit but lets see if you can figure it out............

[Crashtd420]

43 minutes ago, longrod said:

your for getting about the connecting rods, there no way you can clearance the bottom of the cylinder bore enough. 

there's more reason it wont fit but lets see if you can figure it out............

But it has been done....

Check out the link I posted....

L20b block and rods with a z24 crank...

I know nothing more beyond what the poster in the other thread claims...

[iceman510]

It has been done.  20+ years ago were some of first versions.  I have no first-hand knowledge to share though.

[datzenmike]

The rod bearings and journals are the same diameter size and for all intents and purposes the rod bottom ends are the same sizes too if you compare a Z22 and a Z24 rod. The throw is only 2mm wider than the Z22 crank so it can't be that close to the bottoms of the cylinder walls. As I said the counterweights are another matter and are much wider. The Z24 blocks are 20mm taller than the Z22 so the bottoms of the cylinders can be shorter by this amount to clear the throws.     

[longrod]

If it was done 20+ years ago why hasn't it been done since.... If it could be done I'd be running it.

The fact of the matter is it can't be done.  Stop assuming I'm wrong and try to make it work....

You can do it on paper, Hmm........... I wonder what rod length this person uesd 🤨  what piston pin height they used??????

how far it stuck out of the block, or how the crankshaft counter weights hit the piston????

come on all you DATSUN motor builders..... 

[datzenmike]

I think it's making 7 the hard way. There's no valid reason to do this other than to disguise a 2.4 or 2.3 liter displacement as a  L20B/Z20 or Z22 engine. Why not just use a Z24 engine in the first place?

 

All L20B/Z20/Z22 deck heights are 227.45mm. Half the stroke of a Z24 crankshaft is 48mm so there is 179.45mm available for a rod and a piston combination. L20B/early Z22 rods are 145.9mm long leaving a perfect piston height of 33.45mm.

 

You could mill down 85mm bore Z20S pistons or 87mm Z22S pistons 1mm. Or a custom piston made.

 

 

 

 

[longrod]

Well that doesn't work, you would never get a piston to mount on the rod that would clear the counter weights.

 

There are still many reasons...

 

I'll just leave it at that and go back to being a ghost here .................😆

[datzenmike]

All along it's been stated that the counterweights need to be cut down.

 

There's a guy on The Realm that was going to lathe a Z24 crankshaft for a project. I have a private message to him asking how that turned out. 

[longrod]

Well egg on my face,

 

I mocked up the best I could a Z20 block and Z24 crank with a L-20b rod. It can be done.

You would need to turn down the counter weights @12-13 mm, this needs to be done to mount a Stock Nissan Z24 piston on the l20b rod. More then likely you would have to add heavy metal to the crank to get it to balance.

You wouldn't need to take so much off the counter weights if using a custom piston.

The counter weights hit some of the oil pan rail areas, along with the bottom of the cylinder/block. would have to make a custom cover for the crankcase breather area.

The only stock rod you can use would be the L20b 5.75 long rod. with a rod stroke ratio of 1.52, that's a bit low but doable. The bottom of the pin end hole of the rod sits just below the counter weights when at BDC.

[datzenmike]

The Z24 block was modified for crankshaft clearance but oil pans from all L4 and Z series will fit. I have a '76 L20B pan on a Z24 block.

 

The L20B/early Z22 rods are 145.9mm, which is more accurate.