Z20 Forged Pistons

[z20nav]

Hi all, just wondering if anyone knows of any forged pistons that will fit a nissan z20s engine? I've found H beam conrods but yet to find a piston to suit. Cheers all

[ggzilla]

Wiseco custom forged are less expensive than eBay pistons. Call Wiseco at 1-800-321-1364 or message at Contact Us | Powersports & Auto Support - Wiseco

[ggzilla]

Oh, you're in NZ. Well, there's always JP Pistons but they are $$ compared to the top US suppliers

[Stoffregen Motorsports]

JE, Wiseco, Cosworth all make forged pistons for Datsun L and Z motors. Most will be custom, built to spec, but they may have some off-the-shelf pistons in generic shapes and pin heights.

 

What length are the rods you found?

 

I forget the name of the shop, but Rebello is now having their pistons made by a smaller shop in SoCal. They are 100% custom and are a lot less expensive than JE or Wiseco, and their turnaround times are drastically quicker. Wiseco had a 8 month wait time last I checked.

[ggzilla]

? (!)

 

may have been during the pandemic? 8 months is insane

 

1 hour ago, Stoffregen Motorsports said:

Wiseco had a 8 month wait time last I checked

[datzenmike]

North American Z20 stock pistons are 85mm diameter, flattop with very small valve reliefs and the pin height is 31.75mm with stock conrods. Stock rods are forged H beam and very strong. What's this being used for????

 

This combination of crankshaft, (L20B) pistons and conrods are used in the...

 

A10 '80-'82 ('81-'82 in Canada) Z20S

S110 200sx '80-'81 Z20E

720 truck '84-'86.5 (Mileage option) Z20S

[ggzilla]

yea, but don't cheap out, any worthy build deserves forged rods

 

Mike, are you saying that these Z20 engines listed come with L20B pistons from the factory?

12 minutes ago, datzenmike said:

This combination of crankshaft, (L20B) pistons and conrods are used in the...

 

A10 '80-'82 ('81-'82 in Canada) Z20S

S110 200sx '80-'81 Z20E

720 truck '84-'86.5 (Mileage option) Z20S

[datzenmike]

Sorry for the confusion the Z20 used the U60 L20B crankshaft.

 

Jason Gray lists two different piston /rod combinations for the Z20 but for N Am there was only the 152.5mm rod and the 31.75mm pin height pistons. These two numbers plus half the 86mm stroke cannot exceed the block height of 227.45mm (well you can but not by much and too low and you loose compression)

............... rod..........pin height.. stroke

Z20 ..... 152.5mm + 31.75mm + 43mm* = 227.25mm

L20B.... 145.9mm + 38.1mm + 43mm* = 227mm

 

* same crankshaft stroke.

[Stoffregen Motorsports]

Used to be that forged pistons were not great for street engines because they required more piston to wall clearance. That changed in the late '90s when they started machining them to utilize OEM clearances. One benefit to forged pistons is the selection of rings available. You can get low tension steel rings in a very tightly grouped pack on modern pistons. Not the old 3mm cast rings of yore.

 

Yeah, 8 months. Lots of shops still have massive wait times. The excuse I keep hearing is the labor shortage. I don't have first hand knowledge of any labor shortage, but apparently it's still a problem.

[z20nav]

Thanks to everyone that replied and I apologize for replying months later! So I have a 1987 Nissan Navara which is New Zealand new (not imported) more commonly knows as a Nissan Hardbody out side of nz/Australia. 

 

I've extensively been restoring this ute and have most of the stuff to turbo it. My z20s has 4 spark plugs but I hear some have 8. There seems to be so many different variations with these vehicles. 

 

I just want to do my best to make the engine as bullet proof as possible ( I've never had the engine apart and runs fine now) the Scatt Hbeam conrods I can purchase are as follows length 152mm, Centre pin 53mm, big end 22 and wrist pin 21mm. Is there an off the shelf piston that could fit these with my engine? Cheers!!

[z20nav]

Here in NZ I can get pretty much any nissan piston on the market apart from the Z series, probably because there not known for there power, but I want to keep the original engine in the ute. With the tariffs and exchange rate I wouldn't be shocked to find out it would cost me 3-4k for 4 pistons from wiseco etc, but in saying that if I had to go down that road I would when I had the spare $$.

 

 

[z20nav]

https://www.precisionintl.com/products/crniz20ha4sc?srsltid=AfmBOooYBwNriqzWYYZbEV89SpN-VEnRdBkwBP6M6SdDi-GvKLZfefy8

 

This is the link to the conrods I've been looking at

[ggzilla]

The stock pistons and rods are plenty bulletproof, and still working 45 years later. Only if you supercharge or turbocharge will forged pistons shine. The stock parts can handle 10 psi boost, as they do in the Z18 Turbo engine

 

That being said, while forged pistons are expensive if you shop carefully forged pistons are available quite reasonable. That may be why Wiseco has an 8-month backorder

 

As far as off-the-shelf alternatives, I haven't heard of any piston swaps for Z-series engines, like using Subaru pistons in other Datsun engines

 

37 minutes ago, z20nav said:

I just want to do my best to make the engine as bullet proof as possible

[ggzilla]

More like $800/set from Wiseco, and tariff is what, 30%? So maybe $2000 NZD with taxes, tarrifs and and shipping. If your goal is bulletproof, spend the money on better brakes and tyres, and keep the bulletproof factory parts

38 minutes ago, z20nav said:

With the tariffs and exchange rate I wouldn't be shocked to find out it would cost me 3-4k for 4 pistons from wiseco etc

[z20nav]

19 minutes ago, ggzilla said:

The stock pistons and rods are plenty bulletproof, and still working 45 years later. Only if you supercharge or turbocharge will forged pistons shine. The stock parts can handle 10 psi boost, as they do in the Z18 Turbo engine

 

That being said, while forged pistons are expensive if you shop carefully forged pistons are available quite reasonable. That may be why Wiseco has an 8-month backorder

 

As far as off-the-shelf alternatives, I haven't heard of any piston swaps for Z-series engines, like using Subaru pistons in other Datsun engines

 

Thanks mate I don't plan on running more than 6 or 8psi as it's only a summer cruiser that we get out for the odd event. I may aswell continue with the turbo and leave the rest of the engine alone as it won't be getting thrashed. 

 

[banzai510(hainz)]

iF u want longivity keep stock and its free. No tariffs nothing. Pesonally i think nissan rods are already forged. Get arp bolts.

[datzenmike]

Get an oil cooler and a high volume oil pump from a KA engine found in the D21 Hardbody. The internal rotors are 13% longer moving more oil per turn. This increases the hot idle oil pressure and rises faster to maximum pressure at a lower RPM than the stock pump that hasn't changed since the '60s. A turbo is going to dump a lot of heat into the engine oil. 

 

I should imagine your single plug Z20 ignition timing is around 10-12 degrees? A dual plug head is 3-5 degrees because the burn time is much shortened with two ignition points and there is less time for the cylinder to auto ignite. (ping) 

 

6-8 PSI I would keep the stock pistons and rods. You can buzz to 10 PSI but not without good control of your coolant and oil temperatures and a good ignition retard under boost. I would also increase the ring end gap to allow for heat expansion under prolonged boost. For a mild build 0.005" for every inch of bore diameter top and 0.0055" second ring. Again engine temperature control including oil temps are important. Heat is not your friend under boost. 

[Spiff]

I second datzenmike on this, if you're not gonna go more than 8psi then no need for forged pistons or rods. Stock one can probably go even more I ran my Z20 at 10psi for a long time but engine management and tuning has a lot to say here(plus I live in Norway, NZ might get hotter climate depending on where I guess), I ran efi with a megasquirt ecu. Standalone ecus offer a lot in terms of protection which is very valuable for a turbo converted car; oil too hot? reduce rpm limit. Intake air to hot? pull timing. Oil pressure cut? Sure thing! Overboost? Cut. Could mean the difference between going home or waiting for a tow while you're checking markeplace for spare engines 😅

 

 

[z20nav]

On 9/3/2025 at 1:07 AM, datzenmike said:

Get an oil cooler and a high volume oil pump from a KA engine found in the D21 Hardbody. The internal rotors are 13% longer moving more oil per turn. This increases the hot idle oil pressure and rises faster to maximum pressure at a lower RPM than the stock pump that hasn't changed since the '60s. A turbo is going to dump a lot of heat into the engine oil. 

 

I should imagine your single plug Z20 ignition timing is around 10-12 degrees? A dual plug head is 3-5 degrees because the burn time is much shortened with two ignition points and there is less time for the cylinder to auto ignite. (ping) 

 

6-8 PSI I would keep the stock pistons and rods. You can buzz to 10 PSI but not without good control of your coolant and oil temperatures and a good ignition retard under boost. I would also increase the ring end gap to allow for heat expansion under prolonged boost. For a mild build 0.005" for every inch of bore diameter top and 0.0055" second ring. Again engine temperature control including oil temps are important. Heat is not your friend under boost. 

Thanks datzenmike, been following alot of your advice over the years and has been much appreciated. I'm very novice to engine building etc, so learning as I go of course, with the odd costly mistake along the way 😅.

 

So I've purchased a Tomei high flow oil pump, I couldn't find a ka24 one here that wasn't on a very high km motor so went brand new with the Tomei. My understanding is they are a decent brand.

 

Do I need a larger oil sump now? Or is that more a bigger engine issue? Other forums I've been reading (completely different engines though) say that there's potential to starve the engine of oil because of the higher flow pump. Thanks!

 

 

[datzenmike]

Tomei? Usually pricey. Nissan dealer ones are under $100 so NAPA D21 oil pumps are about $50-$75  new.

 

The high volume oil pump has the same output pressure as the stock one. 55 PSI is 55 PSI. Not going to suck the sump dry ever.

[z20nav]

Thanks mate good to no, yes was pricey $275 nz dollars but I've always struggled to find Z parts here and am slowly collecting them as I can afford them. Its for a L20B and looks as though it should bolt up fine, the outfit i brought it from said it would anyway. One day when I work out how to post photos on this forum I'll post some up!

[datzenmike]

The L, Z and KA (external) oil pumps interchange. It's the KA pumps that have the larger internal rotors you want. The 280zx turbo automatic also has a higher volume pump but I've never had one apart. Doesn't look like much but I measured them. The high volume pump rotors are 13% longer

 

 

 

My tired L20B had a hot idle oil pressure of 17 PSI. With no other change than a KA oil pump it jumped to 28 PSI. The oil bleeds past bearings faster than the pump can replace it so at idle the pressure drops. A high volume pump brings the pressure up and reaches the set relief pressure sooner. Usually 50-60 PSI. You can shim the pressure relief spring in the pump to raise the top pressure but usually not needed. Generally 10 PSI for every thousand RPM you expect to run the engine at. A high volume pump is great if you have a spray bar or turbo oil feed added.

[z20nav]

14 hours ago, datzenmike said:

The L, Z and KA (external) oil pumps interchange. It's the KA pumps that have the larger internal rotors you want. The 280zx turbo automatic also has a higher volume pump but I've never had one apart. Doesn't look like much but I measured them. The high volume pump rotors are 13% longer

 

 

 

My tired L20B had a hot idle oil pressure of 17 PSI. With no other change than a KA oil pump it jumped to 28 PSI. The oil bleeds past bearings faster than the pump can replace it so at idle the pressure drops. A high volume pump brings the pressure up and reaches the set relief pressure sooner. Usually 50-60 PSI. You can shim the pressure relief spring in the pump to raise the top pressure but usually not needed. Generally 10 PSI for every thousand RPM you expect to run the engine at. A high volume pump is great if you have a spray bar or turbo oil feed added.

Thanks again mate, any advice on prepping a weber 32/36 for turbo. So far I've got the carb hat and a z18et exhaust turbo manifold which appears to be a direct bolt on, was hoping someone might no away of sealing the carb without losing my choke? If I have to remove it I will though of course!

[datzenmike]

 

 

You'll need a boost referenced fuel pump that maintains about 2-3 PSI above boost. You don't want a 3 PSI fuel pressure trying to pust into a carburetor that is under 10 PSI of boost.

 

If the Weber float is brass it might collapse from the boost pressure. I think there are solid plastic ones.