L18 long rod build .what pistons?

[datsun 160J SSS]

Hello I did a search looking for info on what z20 pistons to get and i cant locate the exact answer z20s and z20e what is the differenceIn.piston?  they look the same when i look for pistons .I plan on building a long rod L18 useing L16 rods and the Z20 piston .do i use the flat top or the dish ?

[datzenmike]

 

Above Z24, Z22, Z20E and L20B pistons.

 

 

There were 3 applications of the Z20 engine. The A10 (HL510) after '79 and the '80-'81 S110 200sx. Both used the same pistons and 6" (152.5mm) rods, they were flat top with tiny eyebrows cut in the tops for valve clearance.

 

The 3rd one was in the '84-'86 720 truck with the Mileage Option package. They also used the same 152.5mm rod and rings but the part number was very different. The mileage option uses a smaller combustion chamber head for 9 to 1 compression. I've done the math and assuming flattops and a 46cc chamber comes out to 9:1 so it can be assumed that they are flattop or very close.

 

I cannot find any mention of Jason Gray's 'Z20S piston with a pin height of 35.56mm'. All the Z20s use the same 152.5mm length rods so the piston pin heights must be the same at 31.75mm. JG doesn't have a dish size or a rod length for this mystery piston either. Of the Z20E he says: "Rod length given as same as Z20E on the incorrect charts, Impossible considering piston pin height! Using 148.6 rod length, the calculations seem much more reasonable but this is entirely unverified. "

 

 

[datsun 160J SSS]

Thanks Datsun mike for the info .any chance you have a side shot of those pistons

[datzenmike]

 

Pretty sure same arrangement. Camera distorts perspective. The last two on the far right Z20 and L20B, should be the same length from piston top to the centers of the rod caps. 152.5 + 31.75 = 184.25mm and 145.9 + 38.2 = 184mm.... close enough.

[datsun 160J SSS]

Thanks Mike. The second rod piston look to be the shortest of them all .do you know if that is the Z20s Piston ? 

[datsun 160J SSS]

[datsun 160J SSS]

Edited December 7, 2020 by datsun 160J SSS
2 of the same post

[datzenmike]

Length distorted by the camera lens.

 

What about over boring your L18 block to 87mm from 85mm and using Z22 pistons on the 133mm L16 rods? Z22 have got to be easier to find. 78/2= 39mm (stroke) + 133mm (L16 rod) = 172mm plus 35.5mm (Z22 pin height) = 207.5mm. You have a deck height of 207.85 so this fits and to spare.

 

I did some maths...

Z22 pistons would make this an 1,853cc engine and with an open chamber L18 head... 8.28 compression and 8.839 with a closed chamber head.

 

You could deck the block 0.5mm or 0.020" and the piston would still be only 0.25mm above and still have lost of room inside the 1.2mm head gasket thickness. This would give 8.8 open chamber and 9.5 closed

[datsun 160J SSS]

L16 rod Z22 piston .I think i have these parts in my stock . so you would still have a long rod L18 .i do have a L18 SSS head from Japan 

[datzenmike]

49 minutes ago, datsun 160J SSS said:

L16 rod Z22 piston .I think i have these parts in my stock . so you would still have a long rod L18 .i do have a L18 SSS head from Japan 

 

Relatively speaking though less than 3mm longer than the stock L18 rods. A rod/stroke ratio of 1.66 changed to 1.70. I doubt you'll notice much and anything you do will be from the small displacement increase.

 

 

SSS head. That would be a 219 casting. Confirm by looking along the lower edge under the #1 spark plug. This would be a 1.5" intake ports, 42mm intake and 35mm exhaust valves in a closed chamber. 

 

On 12/6/2020 at 8:17 PM, datzenmike said:

 I did some maths...

Z22 pistons would make this an 1,853cc engine and with an open chamber L18 head... 8.28 compression and 8.839 with a closed chamber head.

 

 

 

[Stoffregen Motorsports]

Early 219 heads had the casting number on the lower front lip of the head, where it meets the timing cover.

 

 

[datzenmike]

 

Yup and said A87 on the side so you have to look for it..