Noob LZ23

[Jitenshakun]

Hello wise and learned Datsun modifiers. I humbly come to you for knowledge before my build - after reading threads. 

 

On my garage floor I have:

 

- Complete Z22e

- Complete L20b

- A87 head (open chamber) 

- Dreams of a 720 4x4 that moves

 

The LZ23 via an 89mm bore and KA pistons appeals to me, but how far do I go with rods and crank? 

 

Z22 crank vs L20 crank. Pros and cons? 

 

Which rods do I use? Modified L20 rods; if so how?  The Z22 rods? Aftermarket rods? 

 

I'll be runnimg pump gas and don't mind premium. 

 

TIA

[Stoffregen Motorsports]

Due to the short pin height, a long rod 2300 does not use an OEM piston. They have to come from a custom shop, like JE, Wiseco, Cosworth, etc.

 

The rods you need for the long rod 2300 are N85, which come from a Z20. I've heard of guys using off the shelf custom rods from another application that are actually quite inexpensive. I don't know the application though.

[Jitenshakun]

Z20 eh? That sounds tricky to source. An aftermarket option might be easier? 

[Stoffregen Motorsports]

If you can find the right dimensions. As I said, I do not know what the part number is, but I am aware there is a rod out there that has the right journal sizes and is 6" long.

 

But then you will need to order a custom set of pistons.

 

A 2200 uses the same rod, but an L20B crank, which allows you to use a cut down KA24DE piston. So no custom parts. The L20B crank is fully counterweighted too, which is better for balance.

[datzenmike]

Bore Z22 out to 89mm. You could use the L20B but that's a bit much to bore it.

Use L20B rods.

Get a set of 89mm KA24E pistons.

Use the Z22 crankshaft.

Use open chamber A87 L head

Use L20B timing parts and timing cover

Use L20B oil pan... I assume you want this for an L series engine? If using as a Z series engine you will have major problems fitting both manifolds on a left leaning block with steering column and brake booster on a 720. You could more easily fit an L series transmission and lean the engine over to the right

 

You have everything needed but the KA24E pistons to make a  9.78 compression 2288cc (or 2300) engine. No special parts, machining or custom pistons.

 

 

[Jitenshakun]

This is for a Z series equipped truck and tranny so the exhaust and intake manifolds do make for a packaging problem. 

 

I'd have to mock up fitment and possibly look for L20 720 engine mounts to clock the engine left and run a L-series tranny bell housing to match the clocking. 

 

Am I dreaming here? 

[datzenmike]

No. I've done a swap from L to Z24 in my 620. Had a really nice mid ratio '79 280zx 5 speed I liked. Swapped a Z front case onto it and in it went.

[Jitenshakun]

Right, I have a Z and L front case for the tranny so can use whichever. 

 

Are L engine mounts and L tranny on a Z block possible to lean the whole package away from the brake booster? 

[datzenmike]

Absolutely. The engine brackets are what position the lean on any L or Z series engine. The L brackets tilt the block about 12 degrees to the right of vertical while the Z series tilt about 6-8 degrees left of vertical... about 20 degrees of difference.

 

Transmission front cases have the same bolt pattern just that they are rotated left or right to match the engines.

 

The rib is down the center line of the transmission. The two top bolt holes go into the block on either side of the head. As seen the block is rather over to the right of center. For quickly telling which transmission this is just remember hole on the left is L series.

 

 

Here the two bolt holes and the block will be noticeably over to the left. Hole on the right (side) is Z series.

[Jitenshakun]

Sounds like I can use my L engine mounts and L transmission with my Z block and pick up 12deg of lean! 

 

@datzenmike where do you get your numbers for clearance and compression? I saw a post that said the "modifying your L-series" book had sketchy numbers for the Z-series. I'm not questioning you, rather trying to know the sources. 

 

Someone over on FB is saying your recipe is 8.64CR engine based on 145.9mm/92mm.

[datzenmike]

The KA piston is 89mm and the Z22 stroke is 92mm so the swept cylinder volume pi r².... is 572cc. This is the volume of air pushed by the piston.

 

From the crankshaft center line to the top of the block (or 'deck') on the L20B and the Z22, is 227.45mm so if you turn the crank to TDC take 1/2 stroke 92/2= 46mm, plus the L20B rod length of 145.9mm plus the center of the KA piston pin to the top of the piston 34mm and add all that up you get

46 + 145.9 + 34 = 225.9mm leaving 1.55mm above the piston to the top of the block. This space becomes part of the combustion chamber and is 9.63cc.

Assuming a crushed gasket thickness of 1.2mm and with the bore of 89mm this is a 7.46cc volume

The dish on the top of the KA24E piston is also part of the combustion chamber and is 2.8cc

The open chamber L20B head A87, U67 or W58 is 45.2cc

 

Compression ratio is the swept cylinder volume plus the total combustion chamber volume divided by the total combustion chamber volume or

 572cc + (9.63cc + 7.46cc + 2.8cc + 45.2cc or 65.09cc) = 637.09 /65.09 = 9.87873

[Jitenshakun]

Thank you! I wanted to do the math but was missing some of the values. 

[Jitenshakun]

@datzenmike How does LZ20 rod (152.45mm) change things up? 

[datzenmike]

L20B

Well on an L20B that's easy as the Z20 engines have the L20B crankshaft the 152.5mm rods, same deck height and a flattop piston. The rod is longer but the pin height is shorter to allow it to fit in the 227.45mm deck height. The Z20 piston has a pin height of 31.75mm and is 85mm bore for a 10.68 compression 1951cc displacement. 

The VG30 piston height is the same and basically a flattop but is 87mm bore making a 2044cc displacement and 10.12 compression.

 

Long vs. short rods. A longer rod decelerates sooner, lingers near TDC longer, and accelerates away faster than a shorter rod. I suppose it might capture more of the peak combustion pressure and turn into downward motion than a short rod. But rod length is more about being not too short as this adds side loading and friction on the cylinder walls. Certainly don't go shorter than stock rod length but you can go as long as you want but don't go to extremes of effort or money. If longer was that much better all engines would have them so do not expect even a modest improvement. It's a few hp at best like installing the pistons backwards 180 to change the pin off set. Longer rods are going to be heavier.

 

 

[Jitenshakun]

I guess this leaves a question of the cam. Is there an Isky grind that's ideally suited or a set spec to ask for? 

 

The header is going to be a problem for sure. I'm already limited as a 4x4 so this is going to make it that much worse. 

[datzenmike]

Wish you had put that your 720 is a 4x4 as the L20B oil pan from the '80 4x4 will never work in an '81-'86 4x4 that had Z series engines.. 

 

 

[Jitenshakun]

Yeah, but I'm using the Z22 block. Can't I use my Z24 4x4 oil pan? 

 

Z22 block and crank

KA23e pistons

L20 head and rods

Cam? 

Z24 oil pan? 

Edited December 13, 2021 by Jitenshakun

[datzenmike]

There is a 20 degree tilt difference between an L and a Z series engine so the pan will be lop sided.

 

 

 

[datzenmike]

 Stock L20B cams are OK. Increasing the duration also increases the overlap, the time both valves are open together and this lowers the intake vacuum which affects the strong stock idle. This favors higher RPM power making but takes away from lower speeds. It depends on what you are willing to put up with to make more power. A cam can be a let down it not combined with larger or multiple carburetors and a less restrictive exhaust to get the most out of it.   

 

[Jitenshakun]

I'd be going dual Webers and a straight pipe for the exhaust. The oil pan looks like it'll be a pain. 

 

Do you have to do anything with the L20 rods to fit the Z22 crank? 

[datzenmike]

 Rod 152.5mm +  crank 46mm = 198.5mm

The Z22 block is 227.45mm tall so 227.45 - 198.5mm = 28.95 pin height. The closest ones are the 31.75mm Z20E (85mm bore) and VG30E (87mm bore) and both are going to stick up above the block deck by 2.8mm!!!

 

[Jitenshakun]

4 hours ago, datzenmike said:

 

From the crankshaft center line to the top of the block (or 'deck') on the L20B and the Z22, is 227.45mm

Per your post I'll stick to L20 rods in a Z22 block. 

[datzenmike]

All 720 truck Z22 rods are the same as the L20B.

Most 200sx car Z22 rods are the same as the L20B but from Jan '82 on they are different. You would have to measure them too be sure, so why bother if you have L20B rods, just use them..

[Jitenshakun]

I've been doing more looking and stock KA24e pistons aren't an easy option anymore. That said, what about Arias?  The 2 options are a dish and a dome. - 11.5cc vs. 10.4cc. Which one is the way to go?

 

https://www.ojperformance.com/product/arias-forged-pistons-nissan-240sx-s13-s14-89-90-hardbody-pick-up-90-97-ka24e-89mm-std-11-5-cc-8-71-3520300/

[datzenmike]

The KA24E was only used in the '89-'90 S13 240sx not the S14 and had floating piston pins. The truck used the same pistons but were press in pins. Where are you getting the dish and dome numbers? I see -11.5cc and assume this is a dish volume???

 

$600 for forged pistons???? way to much unless boosting.

 

An LZ23 with an 11.5cc dish and open chamber L head would make for an 8.75 compression..... not to bad.

 

An LZ23 with an 10.4cc dome and open chamber L head would make for a 12.02  compression..... not good.

 

Option:

Substitute Z24 pistons with 15cc dish for 8.4 compression. You can deck the block 0.5mm for 8.7:1 compression or 1mm for 9:1 compression. You could also mill the head slightly.