l20b ka24 engine

[justin 620]

Hello, I've been combing this forum for a while, and i haven't been able to find exactly what i'm looking for.

 

I have a running Dastun l20b engine, and i have a blown ka24 2400 12 valve engine out of a 92 hardbody, i've seen several topics about swapping heads and what-not, but i think the head in my ka24 has a whole in it somewhere so i'm not sure if it's usable, but i digress. what i really want to know is about a mod i saw on a different website about swapping out the crank shafts? it said that it would increase the size of the chamber to about a 22? if anybody could lend some advice i would appreciate it!

 

oh, and how do i get this to email me whenever somebody comments on this topic? i'm still new at this : P

[The Stig]

The crankshafts are not really swappable, your L20B crank mains will be too small for the KA block with no suitable bearings, and the KA crank wont fit in the L20 block unless you grind the mains $$ or you align bore the block $$$$.

[datzenmike]

Not much you can swap between L20B and KAEs. If you over bore the L20B block from 85mm to 89mm or cut 0.080" then the KAE pistons will fit. You can use the L20B rods but you will need a Z22 crank. This would give you a Frankenmotor of 2.3 liters. Boring the L20B that much is risky when you could simply use a Z22 block that only has to be bored 1/2 that and already has the correct crank in it.

 

Yes the KAE head will fit but needs an oil drain back hole welded shut and a custom timing chain. At least.

 

_______________________________________

 

You may be thinking of the Z24 or Z24i motor. The crank from that will fit the L20B block, but be warned. The crank throws need to be trimmed on a lathe and the block ground for clearance. I think it's a lot of work for questionable results. You are basically making an Z24 motor using a shorter L block. Having the piston so low in the cylinder and longer stroke will increase side to side thrust loads. Race engines generally are rev happy with longer rods.

[SpudWhitman]

Today I came into ownership of a 510 that has been running an L20b with Z22 crank and pistons since 2005. It blew a head gasket shortly after, but I am under the impression it ran rather problem free once that was sorted.

[datzenmike]

Yes, the L20B and Z22 blocks are virtually identical. The L20B would have to be bored 2mm over, thinning the walls but that's about it. The dip stick hole location is different and there are some differences in the external block casting webs.

[DISLEXICDIME]

you can build a l24 or at least close to it buy sticking z24 parts in a l20 block.

[datzenmike]

you can build a l24 or at least close to it buy sticking z24 parts in a l20 block.

 

It's barely do-able. The L20B has to be bored 4 friggin mm to 89 from 85mm not leaving much cylinder wall left. The Z24 crank won't fit without putting in a lathe and removing 1/2" off the counterweights. The block cylinder bottoms have to be ground down to allow the rods to clear. You can't use the Z24 rods they are 20mm too long but you can use the L20B rods if you mill about 1mm off the Z24 piston top around the outer edge.

[DISLEXICDIME]

i didn't say it was easy i just said you could do it. :P it has ben done

 

i stole this info from some where

Stuff a Z24 crank and pistons into NAPS-Z or L20B block bored to 89mm by cutting down crank counterweights and clearance grinding block as per Ben Pila. This gives you a 2389cc L-series motor that doesnt require using defective (crack prone) Z24 block, fabricating timing cover, lengthening timing chain or modification to close hood. Z24 piston tops will need to be milled down slightly. Fedral-Mogul 33.8mm pin height pistons might not need milling?

Compression ratio with Z24 pistons and open chambered head is 10.25:1 before pistons milled.

parts: : modified Z22 block, modified Z24 crank, modified Z24 pistons, Z22S/ L20B rods

s/2+r+p: 227.7

piston deck height: 0.45 (above deck)

[datzenmike]

I had some pictures of a crank being turned down but.... they are MIA I'm afraid. I was sworn to secrecy on who but will p/m and see if I can get them. Curious how the project is coming anyway. I think the only difference is it's a larger bore Z22 block so less to over bore.

 

The big problem with shortening the deck height is the rod stroke ratio drops from a reasonable 1.79 down to 1.13!!!

 

L20Bs are 1.69

L18s are 1.66,

L16s are 1.80

Z20Es are 1.77

Z22Es are 1.62

 

There is a reason for long rod and shorter stroke motors... they rev higher because there is less side load on the pistons when the crank throw and rod forms a 90 degree bend. This is the point where the rod bottom is furthest off center and pulling the piston sideways in the bore.