What to do with my Z20E? Z24 pistons?

[Spiff]

Hi there, along with my 720 I aquired a Z20E which I intend to replace the stock, completely gutless J16 engine. 

Since I don't know the condition of the engine other then that it ran when the guy pulled it I was gonna do a rebuild, so I'm wondering what to do. 

NA motor or turbo, not decided yet. But I was thinking of just bying a overhaul kit for the z24 and bore it out so the pistons will fit then throw it back together and in to the truck...

 

Will that work or will something interfere in some way?

[datzenmike]

You can get Z24 pistons in 0.5mm and 1.0mm over size. Have the block bored to fit the pistons.

[Stoffregen Motorsports]

I wonder if a long rod 89mm bore KA24DE piston setup would work with a NAPS Z head. Compression wise I mean. I don't think I've ever heard of anybody building a long rod NAPS Z.

[Spiff]

You can get Z24 pistons in 0.5mm and 1.0mm over size. Have the block bored to fit the pistons.

 

Yes, but what about piston height? I think I read somewhere that the z24 has a different wrist pin height than the other Z's, will it hit the valves or will it interfere with the head in some way?

 

I wonder if a long rod 89mm bore KA24DE piston setup would work with a NAPS Z head. Compression wise I mean. I don't think I've ever heard of anybody building a long rod NAPS Z.

 

naps? thats the dual sparkplug setup right? I don't have that, just four simple plugs :)

 

 

 

 

 

Another thing!: I've been reading in the R1 carbs thread and I like what I see, and hear! I was just wondering if there is anything to gain by ditching the old efi setup in favor of the r1 carbs or similar carbs? The l-jetronic efi is analog right and pretty much useless if you wanna tune it...?

Also these engines don't breathe very well in the high rpm range? Boring it out to 89mm would create a slightly oversquare motor which is good for top end so is there any point in doing this or should I just be satisfied with the stock z20's 100 horsepower? I mean, it's still an increase of about 40hp after all.

 

what i was thinking: bore it out to 89mm and use z24pistons, headers, mc carbs if better than stock efi or to just keep the car carbed, a cam if available and some slight portwork.

 

other thoughts: I have only one previous experience with the Z engine and that was a stock z20e with a z24 bottom end, z18et turbo manifold and rb25det turbo, fmic setup. Tons of torque low down but went out of puff at around 45-4800rpms. Good for a pickup or hauling stuff but not in the 910 I had it in, I always wanted more higher up in the rev range. I've had a ca18det powered N13 sunny, a z32 tt 2+2, 280z with a zx turbo swap and the turbo 910 among others, so I guess I like the boost and that was my first thought when I got this current Z20.

But I was thinking of doing something different this time and lets face it, a 720 isn't built for speed. So if I can get 10-20-30 horsepower extra from these mods it's still gonna be a substantial increase over stock and in a 1200kg car it's gonna be enough for some occasional funruns I think....  I still have my motorcycles if I get the need for speed ;)

[Stoffregen Motorsports]

Over here the NAPS Z is a generic term used to describe the Z series head. You're right.

 

But the question remains, would it be worth it to build a long rod, big bore Z20?

[Spiff]

I'm thinking maybe not?

 

But that would require the rods and crank of a 24 too?

[Stoffregen Motorsports]

No, a long rod L motor uses Z20E rods and crank, with a 89mm bore (KA24 or Z24), but the pin height of the piston as well as the dish are the hangups. If you're using a L head, a KA24 16 valve piston can be used but with the top machined for clearance and compression. I don't know what the math works out to with a Z20 head.

[datzenmike]

You said you were rebuilding the Z24 with a kit.
 

But I was thinking of just bying a overhaul kit for the z24 and bore it out so the pistons will fit then throw it back together and in to the truck...
 
Will that work or will something interfere in some way?

I said...
 

You can get Z24 pistons in 0.5mm and 1.0mm over size. Have the block bored to fit the pistons.

Did you mean bore the Z20 out to 89mm and fit the Z24 pistons? Yes you can go that way. It's called a big bore but you will need shorter L20B or Z22 rods. This will make a 2.3 liter engine from your Z20 but with a Z head the compression will be low..
 

[Spiff]

Sorry 'bout the grammar, what I should have said was to buy the overhaul kit for A Z24 engine. 

 

All I have to work with is the Z20E, no L-series engine parts. And they're not easily sourced either over here. So the Z20 is what I have... 

 

The piston pin height of the 24 piston is the problem right? Is there enough material on the pistons to mill them down? 

 

How about Z22 pistons? That would create a 2.1l?

 

I've been reading this post on frankenstein builds: http://forums.nicoclub.com/frankenstein-builds-look-here-for-project-info-t469980.htmlbut that seems to all involve L series head am I right?

[datzenmike]

Yes the Z24 are a higher pin height so a shorter rod can be used to compensate for this. Another problem is the Z24 pistons have a large 15cc dish which will lower the compression into the 7s.

 

The Z20E has a very long rod and there were two Z22 pistons made. All truck and early Z22E pistons are too tall. Only the late '82 pistons are short enough.

 

If you can find a Z22 why not bore the Z20 to 87mm and slip the Z22 crank/rods and pistons in and make it a new Z22???

[Stoffregen Motorsports]

Sorry 'bout the grammar, what I should have said was to buy the overhaul kit for A Z24 engine. 

 

All I have to work with is the Z20E, no L-series engine parts. And they're not easily sourced either over here. So the Z20 is what I have... 

 

The piston pin height of the 24 piston is the problem right? Is there enough material on the pistons to mill them down? 

 

How about Z22 pistons? That would create a 2.1l?

 

I've been reading this post on frankenstein builds: http://forums.nicoclub.com/frankenstein-builds-look-here-for-project-info-t469980.htmlbut that seems to all involve L series head am I right?

The 16 valve pistons can be machined down, but I'm not sure if the compression would be too high or too low or what. I know they have enough material to physically be machined, but someone else is going to have to help you with the CR.

 

I think the problem you may run into with a 87mm bore is pin height, and if it's the same problem as with 89mm bore, why not just go big.

[Spiff]

If you can find a Z22 why not bore the Z20 to 87mm and slip the Z22 crank/rods and pistons in and make it a new Z22???

 

I don't think I have ever seen a Z22 powered car here in Norway, so finding one probably is probably gonna be impossible... 

 

The 16 valve pistons can be machined down, but I'm not sure if the compression would be too high or too low or what. I know they have enough material to physically be machined, but someone else is going to have to help you with the CR.

 

I think the problem you may run into with a 87mm bore is pin height, and if it's the same problem as with 89mm bore, why not just go big.

 

Right, go big or go home  :thumbup:

I don't have the know-how to figure out about compression and that stuff. But if the stock pistons are flattop and level with the top of the block, won't shaving down a bigger piston so it is also level preserve the comp.ratio? Or will it lower it since the bore is bigger? I don't know, that's mathematics I haven't learned...  :wacko:

EDIT: According to a compression ratio calculator I found online, considering all things are equal, increasing bore size from 85 to 89 will increase the comp.ratio slightly. About 0,9:1. But I don't know if all the numbers I put in are correct, uncertain elements are combustion chamber cc's, head gasket bore size and compressed thickness...

 

But when I blew the pistons on that Z24ET engine I had I rebuilt it with wiseco forged pistons and they could basically make what i wanted according to the seller, as long as I provided the measurements. So based on that I suppose they could make me a 89mm Z20 piston, or change the pin height on a z24 piston, but at that point I guess cost comes in to play...  :mellow:

[Stoffregen Motorsports]

I used to build high performance Datsun/Nissan engines for a living while working for Dave Rebello of Rebello Racing, so I have built quite a few of the 89mm bore, Z20 long rod engines, but that was over a decade ago. My memory banks are being purged and I don't have all the data logged in my brain anymore.

 

That said, I do know a KA24 16 valve piston has enough meat on it to cut it down to fit the long rod combo. I don't remember exactly, but I don't think the flat top KA24 12 valve pistons have a thick enough dome to be able to cut it.

 

Yes, Wiseco can build you anything. If you want to get a set of custom pistons made, but aren't sure of the design, call Dave Rebello and buy a set from him or have him tell Wiseco what to make so you can order directly from Wiseco. JE is another good custom piston manufacturer that Dave uses.

 

If you want to be able to do your own engine math, just google "basic engine math" to find some good reading. The only tools you need to mock up and measure a custom engine are: a good, long dial caliper (long enough to measure crank stroke), a deck height gauge (a dial indicator with a 2 legged base), a burette and a variety of cc plates (basically a clear plastic plate with a chamfered hole in it for measuring combustion chamber volume. Add a set of ring compressors http://www.toolfetch.com/gearwrench-850dd-piston-ring-compressor-set.html?utm_source=google&utm_medium=cse&utm_term=CT-850DD&gclid=CPuCxZ_p1cQCFZNafgod3DYAqw, a degree wheel and a flexible base for your dial indicator https://www.shars.com/products/view/18844/Flexible_Arm_Vise_Grip_For_Dial_Indicator and you can build most any engine.