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Truth About L Series Rod Weight and L28ET Ring Lands


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I happen to have pistons and rods from an L24, L28, L28ET and LD28 as well as a 2000 gram digital scale which I calibrated just before measuring began.

 

blue72_all_pieces.jpg

Left to right: L28, L24, L28ET, LD28

 

It has taken me some time to acquire this selection of stock pieces. My only real interest in gathering them was to satiate my own curiosity and share my findings here with the HybridZ community.

 

Part 1: Weight results as well as some general observations

 

Note #1 All rod weights were calculated with the rod bolts and nuts in place. Bearing shells were removed prior to weighing.

Note #2 These weights were taken from individual pieces, not from the average of all six.

Note #3 Your results may vary. Do not taunt Happy Fun Ball©

 

L24E – This engine was in my Z when I purchased it. As it turns out, the early L24E engines from 810 cars have the desirable 133mm rods w/ 9mm rod bolts which are exactly the same as what came in the late L24 engines in the Z cars.

 

 

blue72_l24.jpg

 

Rod Length = 133.0mm

Rod Stamp # = N01-1

Rod Weight = 711.1 g

Wristpin Diameter = 21mm

Wristpin Weight = 120.2 g press fit design

Piston Diameter = 83mm

Piston Weight w/ Rings = 402.0 g

 

L28 – This was a JDM replacement 2bbl carb engine from an emissions era sedan (think Cedric / Laurel / Leopard / Gloria). It wound up in a junkyarded 280Z where I culled its internals.

 

 

blue72_l28.jpg

 

Rod Length = 130.35mm

Rod Stamp # = A87-2

Rod Weight = 727.0 g

Wristpin Diameter = 21mm

Wristpin Weight = 120.2 g press fit design

Piston Diameter = 86mm

Piston Weight w/ Rings = 451.9 g

 

L28ET – Pistons w/ rods purchased from board member

 

 

blue72_l28et.jpg

 

Rod Length = 130.35mm

Rod Stamp # = A87-1

Rod Weight = 711.2 g

Wristpin Diameter = 21mm

Wristpin Weight = 120.2 g press fit design

Piston Diameter = 86mm

Piston Weight w/ Rings = 455.3 g

 

LD28 – Pistons w/ rods purchased from board member

 

 

blue72_ld28.jpg

 

Rod Length = 140.0mm

Rod Stamp # = V07-1

Rod Weight = 789.9 g

Wristpin Diameter = 25mm full float design

Wristpin Weight = 165.4g + 1.3 g each for snap rings

Piston Diameter = 84.5mm

Piston Weight w/o Rings = 523 g

 

In case you've never seen the combustion chamber of the LD28:

blue72_ld28_top.jpg

The bottom of the cast iron cylinder head is flat. All of the fuel and air is compressed into the top of the piston.

 

Interesting note: LD28 rod bolts have a slightly different shoulder than the other 9mm L series bolts.

Left to right: L28, L24, L28ET, LD28:

blue72_rod_bolts.jpg

 

To summarize: The LD28 rods are not some mystical and outrageously heavy pieces with lots of extra mass. They look almost exactly the same as any other L series rods with the exception of their added length and full floating wristpins. There is almost no difference between L28 and L28ET rods. The discrepancy with weight may be because my L28 rods came from a JDM car.

 

Part 2: L28ET ringlands, where they differ from the regular L28

 

blue72_l28_piston_tops.jpg

blue72_l28_side_by_side.jpg

 

L28:

 

Piston Stamp Mark = none

Piston Dish = 10.9cc

 

Top Ringland: 7.2mm

Second Ringland: 3.4mm

Third Ringland: 2.4mm

 

Top Ring Thickness: 2mm

Second Ring Thickness: 2mm

Oil Rings Cumulative Thickness: 4mm

 

L28ET:

 

Piston Stamp Mark = P90

Piston Dish = 10.9cc

 

Top Ringland: 7.2mm

Second Ringland: 4.4mm

Third Ringland: 2.4mm

 

Top Ring Thickness: 1.5mm

Second Ring Thickness: 2mm

Oil Rings Cumulative Thickness: 4mm

 

Interesting Note: The wristpin oiling is done differently on the L28ET piston which has two grooves at the top of the pin instead of the single top hole like on the L28 piston.

 

blue72_l28wristpin_oiling.jpg

 

To Summarize: The two pistons weight almost exactly the same, have the same dish and are both made of cast aluminum. The one major difference is that the second ringland on the L28ET piston is 1mm thicker than its N/A brethren and the top rings were .5mm thinner after 1980. Ringland thickness is a fact that gets thrown around here every once in a while in conjunction with detonation resistance but the real numbers are occasionally misquoted. Just trying to clear up any confusion because as is common knowledge, a picture is worth..... well, you know the rest.

 

 

If anyone else out there has weighed their own rods and has the measurement along with the number stamped in the rod we might be able to get some averages going. If your stock parts look different than what I've shown I'd love to see them as well as know what they came out of.

Edited by blue72
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  • 3 weeks later...

I think you my have some info switched around regarding the l28 and l28et ring thickness, I always thought the turbo rings where the thicker ones... Am I wrong? Bravo on the work though. Currently Im trying to find a way to make my l28et into a ~2.9 with a better rod stroke ratio just for the sake of being different! plus a little machining on some flat tops to add some new age knowledge of spark events. this should be fun!

 

Anyone have any info on what a shorter piston will act? Like will it fight my gains from a better rod/crank ratio?

trying to find a good combo of longer rod and a shorter 87mm piston

Edited by tyler031734
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Nope, this information is correct. This is what I was trying to prevent, the "I think..." or the "I heard that..." sort of comments that get thrown around. I made sure to keep everything orderly and I measured the L28 and L28ET rings and ring lands twice on separate occasions with the same results. It can barely be seen in the pictures if one peers close enough.

 

Truth is that in the U.S., beginning in 1981 (around August of 1980 if you want to be technical) all L28 (both N/A and Turbo) pistons had a 1.5mm top ring (the Laurel wasn't sold in the U.S., so its 1.2mm thick top ring isn't applicable here), 2mm second ring and the customary 4mm oil ring groove.

Edited by blue72
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Nope, this information is correct. This is what I was trying to prevent, the "I think..." or the "I heard that..." sort of comments that get thrown around. I made sure to keep everything orderly and I measured the L28 and L28ET rings and ring lands twice on separate occasions with the same results.

 

AMEN BROTHER!

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  • 4 weeks later...

Did you check the crank journals? I have an L24E with 133mm rods; however, the rod journals are smaller than the z stuff (read will not fit the 240, 260, 280 crank). Nevertheless very good information and thank you for starting the topic. And could you please weight a flat top piston? It would be nice to have it done on the same scale for reference.

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They might not be 133mm rods then. There were two versions of L24E, early and late in the U.S.

 

The early style, like what I posted above, are the same as a late L24 from a Z car. Same 133mm length, same 21mm wristpin, same 9mm rod bolts and the same rod bearing big end diameter of 53mm, etc...

 

The late style came with 135mm length rods which have 20mm wristpins (or possibly 19mm), 8mm rod bolts and a rod bearing big end diameter of 50mm.

 

The same, or very similar rod was used on late L20E and L20ET engines as well. I don't happen to have a set of either to tell you for certain, but if you've got the measurements of the piston pin diameter I sure wouldn't mind adding it to my collection of definitive figures.

 

I'd love to weigh a flat-top piston (I assume you mean L28) and / or rods. Does someone have a loaner or a very cheap used set for sale?

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Since this is a "the TRUTH about these motors" thread, will you be expanding the info to include the L20 (A, B, E) and L16/L18 motors?

 

I've seen talk about using L16 rods in strokers. and if you want L20b data I have a 2 litre L20B 4 cyl in the shed I need to get around to stripping. I could send you the rod and piston data off that.

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Hey, I have an L20A ET piston and rod out of one of my spare engines. Its an M spec. block and the internals are the light duty versions often described in the books as the L24E Maxima spec.(or at least similar to). The engine came out of a JDM R30 Skyline, the year is unknown.

 

Top ring is 1.5 mm's

Second ring is 2.0 mm's

Oil ring is 4 mm's.

 

Rod bolt is 8 mm's

 

Small end is 20 mm's

Big end is 48 mm's

 

As for the weights of the rod, piston and rod length, I can't accurately give those figures ATM, sorry.

 

Hey Kiwi303, I just read your post as I was writing mine..... :)

post-3547-075112800 1283162519_thumb.jpg

post-3547-010083700 1283162540_thumb.jpg

post-3547-095002700 1283162561_thumb.jpg

post-3547-010579000 1283162580_thumb.jpg

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Will you be expanding the info to include the L20 (A, B, E) and L16/L18 motors?

 

Yes, I would like to get my hands on some of each eventually. I've currently got a line on some cheap used L18 pistons. L20a will be a little more difficult for me here in the states, but I'll keep an eye out for a set.

 

I'd like to have one of each if I could. L20 (1965-1969), L20a, L20aE, L20ET (early and late), L23, L24, L24E (early and late), L26, L28E (flat and dished), L28ET, LD28.

Then the fours: L13, L14, L16, L18, L20b, LD20, LD23, Z16, Z18, Z20 (E and S), Z22 (E and S, early and late), Z24, ZD30, etc, etc...

There are still plenty of gaps missing in the info I've gathered for the above engines.

 

 

Thanks for the measurements on that L20ET setup ozconnection. B) If anyone else has info they'd like to share about weights and measures then feel free to help dispel the rumors and myths.

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I should have mentioned that the L20AET specs above are for the "light duty" engine.

 

I have another L20AET which has the "normal" or standard sized rods with 21mm small ends and 53mm big ends and 9mm rod bolts.

 

Below is some information I found out about the nnormal duty L20A rods from Brian who emailed Japan for confirmation

 

"Info I came up with:

 

 

L20 rods are 133.0 mm from center to center... This is the same as the early 240z 9mm rods!!!

 

 

 

Best RegardZ,

 

Brian

Z Car Custom's-JDM

Your Source for KAMEARI & O.E.R.-JDM Products!

www.zccjdm.com

P.O. Box #213

Terrebonne, OR. 97760

541-913-6530"

 

Some engine builder programs list the L20A rods as 135 mm's centre to centre and I've even read in a Datsun book they're 128 mm's. Go figure!

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  • 2 weeks later...

Okay, finally got my hands on a cheap, used set of L18 pistons and rods. I cleaned up two of them in my solvent tank before weighing.

 

blue72_l18_overall.jpg

 

Note: I measured two separate rods because they had different casting numbers. Just like before, these are individual rod weights and not an average taken from multiple pieces.

 

L18 - Pistons w/ rods purchased from ratsun board member

 

blue72_l18.jpg

 

Rod Length = 130.35mm

Rod Stamp # Both A87-1 (rods 3 and 4) and A87-2 (rods 1 and 2)

Rod Weight A87-1 = 690.4 g

Rod Weight A87-2 = 688.4 g

Wristpin Diameter = 21mm

Wristpin Weight = 120.2 g press fit design

Rod Big End Diameter = 53mm

Piston Diameter = 85mm

Piston Dish = 4.36 cc

Piston Weight w/ Rings = 442.6 g*

Top Piston Ring Groove = 2mm

2nd Piston Ring Groove = 2mm

Oil Ring Groove = 4mm

 

*I only had half of a top compression ring to work with, so I doubled its weight and added it to the total.

 

 

This photo may help explain why I was able to acquire these at such a reasonable price:

 

blue72_l18_detonation.jpg

 

Holy flying chunks of piston Batman!

No, I didn't use that piston for the weight above, but rather an intact slug instead.

Edited by blue72
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  • 2 months later...

I have a heavy duty L20e.

Rods are 133mm with 9mm rod bolt shanks

The piston is the odd ball.

Pin Height is 39.9mm not 38.1mm!

Piston is slightly domed. I have no way to accurately measure the CC's of dome.

 

8mm top ring land

2mm top ring

3.2mm 2nd ring land

2mm 2nd ring

2.9 third ring land

4mm oil ring

 

I have no way to accurately weigh anything either. Saw some difference and thought I would post them up...

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