LZ22S Piston For 3.0 L Turbo

[V-Fib]

As my car is slowly coming together I am working on buying all the parts necessary to build my motor and making preemptive plans on a motor build. I have read a few posts on using the LZ22S pistons in the L28 and even members using it as a template for a turbo 3.0 L. Nobody elaborates on the details of their internals. Leaving me with some questions on going this route... 

 

The L28 rods (130.2 mm) + LD28 crank (83 mm) + LZ22S pistons combination. Which would yield a healthy 2960 cc displacement bump with a mere 1 mm overbore to the motor. I don't feel the need to bore the block to 89 mm, it'll give me some extra meat to work with. Furthermore using the LZ22S piston as a guide to create a custom forged piston with a 87 mm bore, 35 mm pin height and 9.33 cc dish volume will net a static compression ratio of 7.4-7.5:1. Which would be adequate compression for a turbocharged application.

 

Eliminating the 4 valve reliefs cut into the piston dish would likely reduce it's volume by ~2-3 cc raising compression into the 7.5-7.6:1 range which is not at all problematic. (Correct me if I'm wrong)

 

As I look at the stock piston for '81 720 that I have in my hands - my doubts and/or questions are:

1. The LZ22S is built for a non-turbo application hence the position/thickness of the ring-lands... would using the same ring land thickness and diameter in a custom turbo application be problematic and cause ring land failure?

2. Would I have to pin down camshaft specs (determine valve lift) prior to ordering a custom piston to see if it will require valve reliefs to be cut? Or if the deck and head of the motor have not been milled is the -1.17 mm deck height of the piston provide enough clearance for the valves?  

 

I have done my fair share of data mining and am a little lost. Hopefully this is not a rehash. Thanks guys.

 

-V

 

 

[Xnke]

I use the Z22S truck piston in +1mm in my 2.9l supercharged engine.

 

I run the L28 crank, L24 rods, and the ITM L22s piston, and compression is higher than you suggest. Total piston dish is 9.3cc, piston is +.010" out of the deck, and I run the fel-pro 0.040" head gasket. With my 40cc head, compression was 9.7:1, with my P90 head, compression is 8.0:1.

 

Running your combo will net you 7.5:1 or so, using a P90 head, as you posted, and the ring pack is exactly the same as the L28et ring pack. Nissan Pistons moved to the that ring pack in 82, turbo or not, and even if the pistons you get are the older ring pack it is clearly not an issue...guys run stocker cast pistons up to 350-400hp all the time.

 

EDIT: I have run cams up to 0.500" lift and 300 degrees seat duration on the exhaust side and still had adequate piston-to-valve clearance. I haven't run a lobe that big on the intake yet.

Edited November 6, 2015 by Xnke

[V-Fib]

Excellent! Thank you very much for clearing up some of my concerns. Wanted to make sure I address all these issues before I start making any move on parts and consulting a builder. 

[510six]

Some years ago my engine builder put together a long block with diesel crank L24 rods and VG30et pistons. With an N42 head I ran about 80 10lb. bottles of N20 through that motor with no ill effects. I personally like the L24 rod VG piston route as your getting a piston already built for forced induction.

[V-Fib]

Good to know, I think that would be a more cost effective solution as well because a set of forged JE pistons for the VG30DETT is in the realm of $1000 which is going to be less expensive then having them cut a piston to custom specifications.

[510six]

Vern at RaVer Motorsports also built another 3 liter , this one with 133mm Cunningham rods and forged 87mm JE VG30 pistons with L series valve reliefs . With a small T4 turbo and a large shot of N20 the motor made 535rwh . Using VG pistons you don't have to resize the L24 rods as the pin diameter is the same at 21mm.

[DAW]

Hi,

Break it down to numbers/specs and don't get too fixated on the source of your parts. By that I mean that there might be a Hyundai or Chrysler piston that better suits your specific need. That's not to say that Nissan parts might eventually end up being your source, especially re 21mm pin dia choices.

 

First set your basic parameters: Stroke (and which rod lengths go with that stroke). 83mm is not a big stroke but in the L block (as opposed to LxxB and LDxx blocks which are 19.7mm taller deck) it is cramped in there so you are going to end up needing a piston with a very short pin ht (comp. ht). It will ultimately become about finding an accessible piston donor source with the needed pin ht, and then arriving at the available piston dia's (std, oversizes, etc) and not the other way around.

 

For 83mm stroke you do not use a 130.45mm rod length even if you get new forged ones for free.

 An appropriate rod length (re rod/stroke ratio) for an 86mm stroke L series is as the L20B is at 145.9mm. You need at least the 133mm length of L24 and L16 (use mid-'72 thru '73 to get strongest rods/bolts; earlier were inferior/smaller). There are some 135-138 'ish rods from Toyota and I'm thinking Saab, and maybe Nissan FJ20? that could work re their cap width and journal diameters. Of these some are nice forged units and some are floating pin, but choosing the Nissan L-series is the easiest way to go.

 

Start with a stock baseline for your calculations, i.e., L28 has 79mm stroke and 130.5 rods and 38.1 c.ht pistons. Every time you do any calculations with stroke length you need to cut those numbers in half for obvious reasons. We are working with distances above horizontal centerline only.

Consider the L28 block ht to be fixed at the factory and you don't even need to know what it is, because add together 130.5 mm + 38.1 mm + [79/2= 39.5 mm] = 208.1 mm.  Then if you substitute the 83 mm crankshaft you are adding (83-79/2 mm = 2 mm) above crank center line that you need to compensate for. Take that off of the c.ht. (38.1 - 2 = 36.1). The 130.5 rods are way too short now for the increased stroke and you'll need 133 mm minimum, so for 133 take 2.5 mm more off of the c. ht.. i.e. (36.1 - 2.5 = 33.6 mm).

 

33.6 mm is not an unusually low pin ht and piston choices/OEM sources will be pretty easy to find. You can look it up but it is more likely that you'll want the Z22E piston (200sx) rather than the truck Z22S piston (720), because the car uses a shorter pin ht. {not surprising: lower rod/stroke needed for a lower rpm range truck vs a car}.  I'm guessing re actual pin ht. difference. You do the arithmetic to check it out.

 

Good luck. 

[DAW]

I looked up the compression ht for the Z22 pistons and the Z22S is 35.56 mm, while the Z22E is 32.1 mm. This is not ideal because the target of 33.6 (above) is in between the two. Ideally you'd want a squish table on the piston top to line up with the flat of the cylinder head chamber (P90, P79, or MN47 heads) even if there needs to be a dished section of the piston top to correspond to the open portion of the chamber in order to keep the c.r. in range.

 

OEM Z22 pistons are not going to stand up to severe loads. If you consider custom pistons then you might as well try to consider adapting them to a more optimum rod length for the 83 mm stroke than the 133 L24 rod is. I have purchased NOS L13 rods (from Canadian Nissan dealership IIRC) before which at 139.9 mm make for a nice combination with the 83 mm stroke. They use 21mm pins which is convenient but the rod bolts are only 8mm, not 9mm.

 

Basically these conflicts re rod/stroke/piston specs are rooted in the fact that the L28 block is too short to increase stroke easily and have geometry work out well. In the LD28 the 83 mm stroke is matched to 140 mm rods and makes an OK rod/stroke ratio, which could be higher than that for high rpm applications (i.e., use L20B @ 146 mm or Z20E @ 152 mm) but these would only fit into the taller LD28 block; never the L28 series.

 

If you chose a 140 mm rod to use with the LD28 crank in an L28 block it would mean:   208.1 mm (from above post) - 140 mm - 39.5 mm - 2 mm = 26.6 mm. That is a very low compression ht even for a custom piston, especially if that piston is using a larger pin dia too. It spells compromise however you do it while using the L28 block and LD28 crank. No free lunch.

 

I haven't looked at these calculations in years but IIRC there is a Toyota rod of 138 mm length and 22 mm floating pin with the appropriate b.e. width and journal dia. At 138 it would match to a piston c.ht. of 28.6. There is an Eco-Tec piston, std size 86mm, that is basically flat top that has a low c.ht.

IIRC it has a floating pin but only 20mm dia. I have no idea if bushing down a rod s.e. for 22mm pin down to match a 22 mm pin is even doable, much less practical.

 

http://www.summitracing.com/parts/wis-k582m86?seid=srese1&gclid=Cj0KEQiA4eqyBRDUh7Omv9vCtsoBEiQAspfs8mhmuZ0xqytty85FvYETUbrul4E0xqrhcP-h4ln8-fEaAssx8P8HAQ

 

The c.ht. is 26.75 mm which is a bit too short for a 138 mm rod (would need 28.6 to be zero deck) but it is very close to the 26.5 mm needed for use with the L13 rod (139.9 mm). The rub is that the L13 rod bolts are only 8mm, otherwise the s.e. for pressed fit 21 mm pin could probably be bushed for the 20mm EcoTec piston pin. L13 parts won't be found in US market but maybe JDM, AU, NZ, etc sources.

 

It's a quagmire but in general it seems that compression hts of pistons in newer engines are lower than in older engine designs so it is worth browsing specs every now and then. see: 

http://www.wiseco.com/Catalogs/SportCompact/CompleteCatalog.pdf

[ryant67]

I pulled these suckers from my previous-owner-built 3.0 stroker motor.  They appear to be Z22S pistons (87mm) with the dish shaved from them, which effectively makes them flat tops, albeit with some useless valve reliefs.  Pin height looks to be around 33.5mm.  

The engine ran L24 rods, LD28 crank, and and E31 head.  Compression looks like it would have been around 10.5:1, and I never experienced any detonation, although the camshaft had .520 lift.  With a P90 head, you would be about 9:1 compression with a stock head gasket.  

Man, was that ever a fun engine, until I spun a bearing anyway...  

 

[DAW]

I agree that that is probably a std size Z22S piston with the top machined to both reduce the c.ht. from 35.56 to 33.5, and eliminate the dish. The valve pockets (that don't correspond to anything on the L engine) might amount to 1 cc of volume vs flat top, if that. You can see that there is still a reasonable amount of ring land material above the top ring. This is a very reasonable approach, although you might want to consider a 1 mm oversize (88 mm) piston to work with in order to improve c.r. if you run the P90 head.

 

You might be able to run a Maxima N47 head if you use std dia 87 mm Z22S pistons but you will need to use a big cam because static c.r. will be almost 11:1. However, the closed chamber of that head provides excellent squish which could help limit detonation problems enough for it to work well.