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#1 kiznook

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Posted 31 July 2007 - 12:46 PM

Here goes, I figure its about time we add this here, Even though we all know where to find it. Quick reference I suppose.

NOTE: all of the following info was "borrowed" directly from the510realm, which was "borrowed" from other outside sources.

#2 kiznook

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Posted 31 July 2007 - 12:46 PM

L series engine internal parts specifications and modifications

While searching for measurements of L and Z motor internal specs, I have found numerous errors in available published data sources. Many of these incorrect measurements originate from the Honzowetz book HOW TO MODIFY NISSAN OHC ENGINE. Honzowetz worked at Nissan Motorsports and appearantly knew Z cars but he really neglected the quality of the 4 cylinder info in the book. Even Nissan Motorsports catalog specifications are not always correct, they are sometimes guilty of truncating important decimals. The incorrect specs from the Honzowetz book were re-published in a 510 again backissue and are found on other enthusiast websites (datsuns.com, ugly datsun page). Do not trust everything you see! I have not completely verified all this data myself, it is just my best attempt to straighten out the prevailing confusion. Verify specifications yourself before buying parts!

The block heights listed in the Honzowetz book for the different L and NAPS-Z motors are the height from the oil pan surface to top deck. This is not a particularly useful number if you are trying to compute piston deck height at TDC. I researched a bit and came up with the more usefull measurements for height from crank centerline to top of block. With the crank centerline-to-deck measurements inhand, it was easy to see that there were some mistakes in the rod lengths in the Honzowetz data, especially among the NAPS-Z motors. I was able to double check some of the suspicious measurements in other sources. Knowing the crank stoke, deck height and piston pin height, I was able to make some reasonable guesses as to what rods Nissan actually used in different motor to achieve near zero deck height of the piston at TDC. (most of the L, Z series have the piston slightly below the block deck at TDC). With the corrected information, I experimented with a spreadsheet to design some hybrid crank, rod, piston, block combination. HOW TO MODIFY recommends not letting the top of the piston protrude further than 0.3mm above the block at TDC. The following is what I have come up with. Please comment if you have verifiable corrections to any of my measurements. Did I miss any other useful combinations?

A NAPS-Z20, Z22 or Z24 block can be modified to use a L-series cylinder head for better performance potential. A stock NAPS-Z head probably has performance equal to a stock L series head but modification potential for the NAPS-Z is limited. Altho a crossflow head may seem like a better design, the NAPS name is an acronym for Nissan Anti Pollution System and this head was not designed with serious performance or modification potential in mind. The Z20E head I examined had 37mm intake ports and 42mm intake/ 38mm exhaust valves and 45cc (dual plug) open chambers. The ports are set too low so there is a sharp bend in the port "shielding" much of the valve and little porting can be done due to close proximity of water jacket. The valvetrain geometry prohibits the use of larger intake valves or high lift/duration camshaft because the valves would contact eachother. It is possible to modify in order to adapt a L series head onto a NAPS-Z bottom end. Building a L/Z hybrid engine is much more envolved than just bolting the necessary parts together. If you have never rebuilt an engine or dont know what you are doing, just stick with a L20B swap! Further advice for converting NAPS-Z block to use L series head is HERE.

For compression ratio calculations, take into account the cylinder head chamber volume (see http://www.pl510.com/cyl_head.htm ), dish volume in piston top, volume contained within head gasket (crushed thickness is 1.2mm), chamber volume created by or occupied by the piston due to non zero deck height at TDC cylinder and the swept cylinder displacement (Pi*r^2 * stroke),.

Compression ratio =(total chamber volume at TDC+swept cylinder displacement)/(total chamber volume at TDC)

Example, stock L20B = (45.2cc + 11.36cc + 7.0cc +2.6cc + 488.0cc) / (45.2cc + 11.36cc + 7.0cc +2.6cc)= 8.4:1


Connecting rods
Center to center length, all use the same 21mm diameter piston wristpin.
L18, L28, L26--------------130.2mm
L16, L24---------------------133.0mm
L13----------------------------139.9mm
L20B, Z22S, early Z22E-145.9mm*
Z20S,- ------------------------??**
Late Z22E-------------------149.5m*
Z20E--------------------------152.5mm
Z24, KA24-------------------165.0mm


*Through 12/81, the Z22E used exactly the same rods, pistons as the Z22S. After 12/81 production date, longer but weaker looking rods were used in the Z22E. Motorsport catalog list the Z22E as having 148.6mm rods but if you order these (12100-D8110) you will get the 149.5mm rods. I am not sure if the 148.6mm rods exist or were ever used in stock applications. Part # 12100-A7660 is a 148.6mm rod but uses 23.5mm wristpin diameter, might work well with bronze bushing to reduce to 21mm pin size.

**Z20S rod length given as same as Z20E on the incorrect charts, Impossible considering 35.56mm piston pin height! Please contact me if you have a verified length for Z20S rod.

Pistons
Piston pin heights (center of pin to top of piston) / piston dish volume/ stock bore
L13, L24-------------38.1mm / 0.0cc dish / 83mm bore
L16, L26------------ 38.1mm / 7.01cc dish / 83mm bore
L18------------------- 38.1mm / 4.36cc dish / 85mm bore
L20B------------------38.1mm / 11.36cc dish / 85mm bore
L28 (early)---------- 38.1mm /10.90cc dish in 280Z, early ZX.('75-'80)/ 86mm bore
L28 (late)------------ 38.1mm /0.0cc Flatop in '81-'83 ZX / 86mm bore
Z20S------------------ 35.56mm / ? dish / 85mm bore
Z22S, early Z22E-- 35.5mm* / 9.32cc dish / 87mm bore
Z22E, late------------32.1mm **/ ? / 87mm bore
Z20E------------------ 31.75 / approx 13cc dish / 85mm bore (Ive also seen flattop Z20E pistons).
Z24-------------------- 34.0mm, / 15.0mm dish / 89mm bore
KA24----------------- 34.0mm / 2.8cc dish / 89mm bore
VG30E--------------- 31.75mm/ approx. 1cc dish/ 87mm bore


* Actual measurements of Z22S pistons yield 35.5mm. Honzowetz chart shows Z22S pin height at 35.0mm. There may also be 35.0mm pistons available?

** Actual measurement of late Z22E pistons have pin height of 32.1mm. Honzowetz chart shows Z22E pin height at 32.5mm. There may also be 32.5mm pistons available?

Note- there are two types of VG30E pistons, using eithor pressed in piston pins or full floating wristpins. The later full floating pinVG30E pistons have been verified to interchange with LZ series rods (with oil hold modification to rod). VG30ET (turbo) engines use larger non-interchangeable wristpins.

Piston information is published in the Federal-Mogul Pistons and SilvoliteCatalogs. Pin diameter height, ring pack type & position, piston crown configuration. Check out the silvolite online catalog for possibilities of non-nissan piston swaps. Most engines use wristpins larger than the datsun 21mm size, it might be possible to enlarge the connecting rod small end hole for the piston pin for non-nissan pistons with larger pin. (Or stay with nissan 21mm pin and use bushings between pin and piston?) BTW- some of the specs in the silvolite catalog for nissan pistons dont match other specifications I have seen, I would be suspicious of the silvolite specifications.


Engine Blocks
Block deck height, (crank centerline to top of deck)
L13, L16, L18, L24, L28: 207.85mm
L20B, Z20, Z22, L28diesel: 227.45mm
Z24, KA24: 247.45mm
Among the "medium" height 227.45mm blocks, it is rumored that the Z20S blocks have the thickest cylinder walls and can tolerate the largest diameter overbore because the Z20S blocks have the cylinders castings "siamesed" together without coolant passages between cylinders (like the L20B, Z20E and Z22 blocks). I have heard that some Z20E might also have siamesed cylinders but the Z20E block I checked was definitly non-siamesed.


Assembled stock engine deck height
L16 ('68-'73 510 and later years 521pickup)
bore 83mm, stroke 73.7mm
(stroke/2)+connecting rod+ piston pin height = 207.95mm
piston deck height: 0.10mm (above block)

L18 ('73-'74 610, and 620 pickup truck)
bore 85mm, stroke 78.0mm
(stroke/2)+connecting rod+ piston pin height = 207.3mm
piston deck height: -0.55mm (below block)

L20B (various '75-'80 610, 710, 200sx, HL510, pickup truck)
bore 85mm, stroke 86.0mm
(stroke/2)+connecting rod+ piston pin height = 227.0mm
piston deck height: -0.45mm (below block)

Z20E ('80-'81 200sx)
bore 85mm, stroke 86.0mm
(stroke/2)+connecting rod+ piston pin height = 227.15
piston deck height: -0.30 mm (below block)
These motors can come with eithor flattop or dished pistons.

Z20S ('80-'81 HL510)
bore 85mm, stroke 86.0mm
(stroke/2)+connecting rod+ piston pin height = 227.16
piston deck height: -0.29 mm (below block)
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.

Z22S ('81-'82 720 pickup) , early Z22E 7/81-12/81 200sx)
bore 87mm, stroke 92.0mm
(stroke/2)+connecting rod+ piston pin height = 227.4
piston deck height: -0.05 mm (below block)

Late Z22E (1/82-2/83 200sx)
bore 87mm, stroke 92.0mm
(stroke/2)+connecting rod+ piston pin height = 227.6 mm
piston deck height: +0.15 mm (above block)

Z24 ('83-'86? 720 pickup)
bore 89mm, stroke 96.0mm
(stroke/2)+connecting rod+ piston pin height = 247.0mm
piston deck height: -0.45 below deck (using 34.0mm pin height pistons)

Fedral Mogul Z24 piston pn 13013P has pin height of 33.8mm, and unspecified "recessed
head w/4 valve reliefs

#3 kiznook

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Posted 31 July 2007 - 12:47 PM

Frankenstein motors:
collect all the parts at pick-n-pull JY and buy it as a rebuildable $50 short block


Medium block 2.4 Liter.
Stuff a Z24 crank and pistons into NAPS-Z or L20B block bored to 89mm by cutting down crank counterweights and clearance grinding block as per Ben Pila. This gives you a 2389cc L-series motor that doesnt require using defective (crack prone) Z24 block, fabricating timing cover, lengthening timing chain or modification to close hood. Z24 piston tops will need to be milled down slightly. Fedral-Mogul 33.8mm pin height pistons might not need milling? Click HERE for Bens write-up of necessary modifications.
Compression ratio with Z24 pistons and open chambered head is 10.25:1 before pistons milled.
parts: : modified Z22 block, modified Z24 crank, modified Z24 pistons, Z22S/ L20B rods
s/2+r+p: 227.7
piston deck height: 0.45 (above deck)


Stroker 2.3 Liter
Stuff a Z24 crank into a modified Z20/Z22/L20B block by cutting down counterweights as above.
No piston modification or block boring needed for 2283cc L series.
see http://hobbslaw.niss...om/custom2.html for an example
Russ noted that his deck height measured -1.77mm with the Z22E pistons that he first tried using, he eventually used milled Z22S pistons to achieve a higher compression ratio.
Parts: Z24 crank, Z22E pistons, Z22S/ L20B rods in a Z22 block or +2mm bored Z20/L20B block.
s/2+r+p= 96/2+145.9+32.1= 226.0 mm
piston deck height: -1.45mm below deck


Big Bore 2.3L
KA24 pistons into a bored Z20/Z22/L20B block. The small 2.8cc dish area of the KA24 pistons helps to preserve compression ratio even with the low piston deck height. Compression ratio with a open chambered U67 head is 9.9:1 or use dished Z24 pistons and peanut chambered head for 8.9:1 compression ratio.
Parts: Z22 crank, KA24 pistons, Z22S/ L20B rods in a +2mm bored Z22 block or +4mm Z20/L20B block.
s/2+r+p= 92/2+145.9+34.0= 225.9 mm
piston deck height: -1.55mm below deck


Longrod 2.19L/2.24L
Start with VG30E pistons and have the tops milled by 2.7mm to produce 29mm pin height. Custom pistons of similar specifications would also be recommended. Using the long Z20E connecting rods gives this engine a better rod/stroke ratio of 1.66:1. (stock Z22 rod/stroke ratio is 1.59:1). Start with +1mm VG30E pistons and bore the block +1mm to 88mm to gain a bit more displacement (2238cc). This engine with custom 89mm pistons is rumored to be the basis for the "rebello 2.3L".
parts: Z22 crankshaft, Z22 block, Z20E rods, milled VG30E pistons.
s/2+r+p: 227.5mm
piston deck height: +0.05mm (above block)



Long rod 2.1 L
I really like the possibilities for this 2.1L longrod motor. For a more in depth analysis of this motor click HERE.
Parts: L20B crank, Z22E pistons, Z20E rods in a Z22block or Z20/L20B block bored +2mm
s/2+r+p: 227.9mm
piston deck height: +0.05mm (above block)



Long rod L18
flattop Z20S pistons and peanut chamber head for 9.7:1 CR, better rod/stroke ratio for higher RPM.
Parts: L18 crank, L18 block, L16 rods, Z20S pistons
s/2+r+p: 207.66mm
piston deck height: -0.29 (below deck)


Low compression combinations for use with turbochargers

Turbo 2.2L
7.87:1 Compression ratio with 45.2cc open chambered head.
Parts: Z22 crank, 2.2E pistons, Z22S/L20B rods in Z22block or Z20/L20B block bored +2mm,
s/2+r+p: 224.4
piston deck height: -3.45 (below block)



Medium-Long Rod Turbo 2.05L
Use 32.1mm piston, 149.5mm rod from late Z22E. These rods are not as sturdy as onther L series rods.
Parts: L20B crank, Z2.2e pistons, Z22e rods, Z22 bock or Z20/L20B block bored +2mm over
s/2+r+p: 224.1
piston deck height: -2.85 (below block)


Short Rod L16
This is my current low compression L16 for turbo use.
7.8:1 CR using 37cc cylinder head. Lowering compression of a L16 would be easier by just installing a open chambered L20B head and using stock bottom end. I just wanted to utilize a good 37cc head I already had.
parts: L16 crank, L18 rods, L24 (flattop) pistons, L16 block.
s/2+r+p: 205.2mm
piston deck height: -2.70mm (below deck)



Turbo L18
Use deep dished L20B pistons in a otherwize stock L18 for 7.63:1 compression ratio (using open chambered head) or bore +1mm and use dished 280Z pistons for 7.85:1 compression ratio.

#4 kiznook

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Posted 31 July 2007 - 12:49 PM

More on the infamous...

Long rod 2.1L motor
parts: L20B or Z20 crank, Z22E pistons, Z20E rods in a Z22 block or +2mm bored L20B/Z20 block

This would be the best HIGH REVING, increased displacement, high compression, engine you could build from the mdium height L20B/Z20/Z22 size block. A "standard" L/Z 2.2 would have 5% more displacement and better midrange torque than this engine but the 2.1 longrod motor with 86mm fully counter weighted L20B/Z20 crank will suffer less vibraton at high RPM than the 1/2 counterbalanced Z22 crank and the hybrid 2.1L will have a slightly oversquare bore/stroke ratio, so better reving than the Z22 "truck engine".Rod to stroke ratio of the 2.1L motor is 1.77:1. Of all the possible L series motors only the L16 has a higher rod/stroke ratio (1.80:1). The long Z20E rods will reduce stress on pistons and help to make more HP at high RPM. The 1.5mm thick Z22E piston compression rings are thinner than 2.0mm L series piston rings so put less stress on the piston ring lands and are less prone to flutter at high RPM. In short, this motor should be a screamer if you build it well, balanced the rotating assembly, and use a suitable RPM cam, head and induction system.

The HOW TO MODIFY bible cautions against allowing the piston to come further than 0.30mm above the deck top, when built with 32.1mm pin height late Z22E pistons (1/82 and later), this motor when build would have the piston tops 0.05mm above. The "bad" honzowetz spec chart list Z22E pistons as having 32.5mm pin height so verify that you have the correct pistons.

With a high duration cam and high octane gas to reduce risk of detonation, you should be able to use a peanut chambered head to get higher CR and better chamber shape. The peanut head will be more detonation resistant for a given CR vs a open chambered head. If you are re-using old Z22E pistons, they will be 87mm. Engine displacement will be 2044cc.If you are buying new pistons, get Z22E pistons in +1mm oversize, 88mm and bore the L20B or Z20 block +3mm to 88mm or convert a Z22 block and bore only +1mm. Engine displacement with 88mm pistons will be 2092cc for a near true 2.1L motor. Did I mention that this motor make HP at high RPM!??

With 87mm bore, 86mm stroke producing 511cc of swept cylinder area, 9.32cc piston dish, 7.0cc gasket volume and the piston raised up above top of block by .05mm, using an open chambered head (U67 or A87) of 45.2cc volume, I calculate a CR of 9.31:1 or, if you used a 41cc peanut chambered head head, CR of 9.92:1. Check and verify the piston dish area and piston deck height!

Since planning this motor, I have realized that it should be possible to use VG30E pistons in this engine instead of the Z22E pistons. I am just not sure if the VG30E piston pins would be compatible with the L series connecting rods, I have seen conflicting specs for the VG30E piston pins that would/would not work depending on who is right. As far as I can tell, the earliest VG30E pistons used wristpins pressed into the rods while the later VG30E pistons use full floating rods retained by circlips.The pressed in pins should work on the L series rods (measure and verify!) of if you use full floating pistons, ensure adequate clearance between wristpin and conncerting rod hole and it will be necessary to drill oil supply holes in the connecting rod to splash lubricate the pin bore. The VG30E piston pin height is the same 31.75mm as Z20E pistons so the piston top would not protrude above the block thus no modifications to piston would be necessary. Compression ratio would be slightly higher with the VG30E pistons because they do not have the large piston dish of the Z22 pistons.

#5 kiznook

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Posted 31 July 2007 - 12:50 PM

How to put an L-series head on a Z block

To use the NAPS-Z block with an L series head, you need to use all the parts foreward of the block from an L20B. Use the front timing cover to match the L series head pattern as the NAPS-Z is slightly different shape where it seals to head around the timing chain. You also need the longer L20B timing chain and matching gears, guides, tensioner and longer L series distributrer drive spindle. The NAPS-Z blocks lack a chain oiler peg. You could drill the block and add a chain oiler peg but this is probably unnecessary since L series front cam tower and the chain tensioner both oil the chain. Im told the L28 6 cylinders didn't even use a oiler peg. Drill a dipstick hole on appropriate boss on right side of block and plug the left side dipstick hole since it will now be covered by exhust manifold. Use an L series dipstick and tube in the new hole, the NAPS-Z dipstick wrong length. Use an original 510 L16 oil pan and oil pickup, NAPS-Z or L20B oil pan wont clear the 510 crossmemember and steering. You will need a headgasket with larger bore if cylinders are over 86mm. The cheap but difficult solution is to use a NAPS-Z headgasket. The shape of the timing cover to cylinder head gasket surface is different between L series and NAPS-Z, headgasket modifications are necessary to seal front cover section if using the larger bore NAPS-Z head gasket (use an entire NAPS-Z gasket and seal the front cover with silicon or cut and splice the front segment of a L series gasket onto a cut NAPS-Z gasket.) The NAPS-Z gasket lacks the valve "eyebrows" so the gasket bore is a true circle, this would prohibit beneficial grinding of the head chamber and block to unshroud the valves, probably best to use the 89mm Z24 gasket even if on a 87mm Z22 block since it will allow the most unshrouding within cirular bore. The NAPS-Z block has all the water passages of the L series (plus a few extra) however the NAPS-Z gasket covers some of these coolant passages that should be open for an L series head, drill holes in the NAPS-Z gasket to match an L series gasket for correct coolant circulation. Even easier to assemble, buy the expensive Nissan Motorsports 88mm big bore L-series gasket. The opening of the cylinder head oil passage at the headgasket should be elongated to better match to the oil passage of NAPS-Z block.

The NAPS-Z20E block that I checked had headbolt threads same as L20B block but I have heard that some NAPS-Z blocks have the headbolts threads deeper in the block hole, you can obtain more clamping force for headbolt by using all long length headbolts (turbo 280zx headbolts part #11059-P7600). Countersink or mill down the upper face of cam tower by 0.5" where headbolt contacts camtower so the headbolt sits 0.5" lower into block. For headbolts that do not thread through camtowers, use .350" thick washers below the longer headbolts to keep them from bottoming out in hole.

For the taller NAPS-Z 2.4 block, do all the above modifications, lengthen the L20B timing chain by adding 4 extra links of datsun chain using 2 master links from a Mercedes-Benz timing chain (#000997-0598), lengthen the L20B timing cover to seal the extra 3/4" block height (welding and machining involved), and modify motor mounts/oil pan so engine sits low enough to close hood. (or use hood scoop!) Another method I have heard of is to space the entire front x-member downward from the chassie and then relocate the controll arm pick-up points upward. Ground clearance to oil pan will be minimal. Most used NAPS-Z 24 blocks will be cracked around at the headbolts, finding a good used core can be difficult.

#6 DISLEXICDIME

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Posted 31 July 2007 - 05:37 PM

or just go to the620.com

#7 kiznook

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Posted 31 July 2007 - 11:22 PM

I know, but I wanted it HERE!!! seems like a good thing to have local (to the site)

#8 datzenmike

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Posted 01 August 2007 - 06:25 AM

Yes. It needs to be added as a sticky, put up somewhere easy to get and refer to instantly. I have this and others under 'favorites' and can access it quickly to check facts.

#9 ]2eDeYe

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Posted 01 August 2007 - 07:21 AM

Stuck ;)

Smokin' Joe's House of Datto's

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620 KA24 Motor Mount Swap Brackets

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Whenever I think that I'm out of my mind for putting this much time and money into an old Datsun, all I have to do is look some of your threads to know that I'm not nearly as whack as you are.

You're going to skin a few knuckles, stand up too fast and bump your head, hunt around the floor for the nuts and bolts you dropped, invent a few new cuss words and when you're finished you'll say "That wasn't so hard after all!"


#10 fiveNdime

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Posted 10 December 2007 - 07:05 PM

If your going to take the Z22 motor and put KA24 pistons in it be sure you get your block from a Z22S ('81-'82 720 pickup). The reason is HUGE! The water jackets on these year motors were further away allowing for the larger bore. Any other ones will give you overheating problems. One more thing. LOOK for the block to be cracked out at the middle stud hole for the head. People tend to bolt the head back down without tapping out and cleaning it. The head bolt then bottoms out and cracks the block right where the water jacket is....bad news....but you must look. If you get lucky you'll find one. I bought my block off of a guy who bought, I think 5 before he found a good one.

Good info Gee!
you found me any rims for the 521 yet?
:thumbup:FiveNdime

#11 datzenmike

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Posted 10 December 2007 - 10:37 PM

The cylinders are also Siamesed together on the Z22S. If I remember right the S stands for Siamese and not carb.

Interestingly, my spare Z24 also has webbing between the bores and also a small hole drilled diagonally down and to the side to allow coolant up between the cylinders and into the head. This would be the hottest part of the bore and needs the cooling near where the top ring is.
Posted Image

#12 Guest_DatsuNoob_*

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Posted 09 July 2008 - 09:10 PM

cant remember where to find the head chart with all the casting numbers and specs. I've looked at it a couple times in the past, but cant remember where I found it. Anybody? Thanks.

#13 yello620

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Posted 09 July 2008 - 09:14 PM

http://www.olddat.co...h/head_ID_2.htm"

#14 kiznook

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Posted 09 July 2008 - 09:31 PM

Jason, that link doesn't work

#15 Gensaiken

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Posted 09 July 2008 - 11:44 PM

http//www.olddat.com/html/tech/head_ID_2.htm

Posted Image
1971 2dr Datsun 510 - L20b, 219 SSS Head, Roundtop SU's


#16 The Stig

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Posted 29 May 2010 - 02:37 PM

This is a great sticky...but

A NAPS-Z20, Z22 or Z24 block can be modified to use a L-series cylinder head for better performance potential. A stock NAPS-Z head probably has performance equal to a stock L series head but modification potential for the NAPS-Z is limited. Altho a crossflow head may seem like a better design, the NAPS name is an acronym for Nissan Anti Pollution System and this head was not designed with serious performance or modification potential in mind.



Actually that's not entirely true, The NAPS name does NOT refer to the head design but to the emmisions package on versions of the Z motor that was also applied to the CA20 in the Stanza and other vechicles, the Z series head first appeared in 78-79 on the first JDM S110 Z18, BEFORE NAPS was introduced, but it was based on the YB crossflow Rally RACING option head for the L6 motors, and the OHC G series motors from the skylines. The stock the crossflow head IS more efficient than all but the SSS or FIA L heads, and therefore cleaner too, as an example the 1.8 G18 has similar HP as L20B. I don't know why the Z head gets such a bad rap, it would be an excellent stock (cheap) head upgrade with the EFI manifolds from a 200SX (and for a turbo), especially in areas with emmisions that make side-drafts problematic. And the design lives on today in Nissan's utility NA20 and NA24 which is a KA bottom end with a Z series head, no NAPS no 8 plugs

Also as to the misinformation in the official literature, I have a FSM for a late 70s 710 or A10 with an L20B that lists the L20B crank as having the small 54mm main journals like an L18, I doubt this is true .... has anyone seen/held a small main L20B crank?

#17 datzenmike

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Posted 29 May 2010 - 03:24 PM

This is a great sticky...but



Actually that's not entirely true, The NAPS name does NOT refer to the head design but to the emmisions package on versions of the Z motor that was also applied to the CA20 in the Stanza and other vechicles, the Z series head first appeared in 78-79 on the first JDM S110 Z18, BEFORE NAPS was introduced, but it was based on the YB crossflow Rally RACING option head for the L6 motors, and the OHC G series motors from the skylines. The stock the crossflow head IS more efficient than all but the SSS or FIA L heads, and therefore cleaner too, as an example the 1.8 G18 has similar HP as L20B. I don't know why the Z head gets such a bad rap, it would be an excellent stock (cheap) head upgrade with the EFI manifolds from a 200SX (and for a turbo), especially in areas with emmisions that make side-drafts problematic. And the design lives on today in Nissan's utility NA20 and NA24 which is a KA bottom end with a Z series head, no NAPS no 8 plugs

Also as to the misinformation in the official literature, I have a FSM for a late 70s 710 or A10 with an L20B that lists the L20B crank as having the small 54mm main journals like an L18, I doubt this is true .... has anyone seen/held a small main L20B crank?


We generally refer to the Z series motors as NAPS but this is for Nissan Anti Performance System. :lol: But yeah I agree it got a bad rap. Stock they are a good motor but they do have limitations if planning to up grade the performance.

Horse power is made almost exclusively in the head and head design. In theory, doubling your RPM will double your hp but only if air flow can keep up. If you make 100hp at 4K you should be making 200hp at 8K. Good flow equals good power and the NAPS, sorry, the Z series flows poorly at high RPMs. The biggest contributor to this is that the intake and exhaust ports are too low with a sharp bend just before the valve. It must be noted that this motor was designed for low pollution at RPMs normally seen on the highway say 4K or so, and for this, good high RPM flow wasn't a concern. The usual methods for increasing flow don't really apply on the Z series. Moderate lift and overlap cams can cause the valves to touch as can replacing with larger diameter ones. Porting can help but not fix a 'bad' design.

Nissan did have some positive things with the Z series. Dual spark plugs. Two ignition sources, shorter burn time equals less ignition advance. Hemi combustion chambers generally regarded as the most efficient and detonation resistant. Cross flow design for more efficient homogenized mixing


The four cylinder 5 bolt cranks were 2.1631" or 54.9mm while 6 bolt L20B and above were 2.36" or 60mm. I have an '84 FSM for the 720 truck and the Z24 crank is erroneously listed as 54.9mm so I have measured two Z20, two Z22 and at least two Z24 cranks to find that they are 60mm.




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#18 The Stig

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Posted 29 May 2010 - 04:10 PM

It must be noted that this motor was designed for low pollution at RPMs normally seen on the highway say 4K or so,



I respect your opinion, and you guys keep saying this but can't back it up, this motor is simply an evolution of the L20B motor to keep getting power out of of the design as emmisions got added over the years, the Z design applies only to the head as the bottom end was (as you know) all L series, and it was for efficiency 1st, emissions second. the YB head it was based on was designed for solely for racing. So I dont know where that "designed for emmisions" statement came from, but I say BS :D it was designed to offset the power loss caused by the emmision de-tuning and more likely to improve fuel mileage under load.

Look were beating a dead horse here, since the arrival of the 12v KA the Z is an obsolete POS, the stock z heads we got here are very poor castings with heavy casting flash shrouding the seats and a harsh angle in the port, but my L20B was no jewel either. But with just mild porting and cleanup it flows much better (I bet as good as ANY stock L head we got). But yes the L series can have bigger valves and cams and $ and yup it be a TON better. But by the the 1980s nissan works performance (the factory) decided this was a superior head and used it for racing along with the DOHC LZ heads from JDM formula 3 for turbo apps, the 8v L heads were obsolete old school by then, look up George fury's Z18ET stanza and you might find some picks of that motor (no L head but it did have 8 plug distributor) I could email you a pick if you can post it. But yeah if you can afford it, big valve L or KA is the way.


PS does that mean you HAVE seen a L20B 54mm crank and it has 5 bolts?

#19 datzenmike

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Posted 29 May 2010 - 06:46 PM

I respect your opinion, and you guys keep saying this but can't back it up, this motor is simply an evolution of the L20B motor to keep getting power out of of the design as emmisions got added over the years, the Z design applies only to the head as the bottom end was (as you know) all L series, and it was for efficiency 1st, emissions second. the YB head it was based on was designed for solely for racing. So I dont know where that "designed for emmisions" statement came from, but I say BS :D it was designed to offset the power loss caused by the emmision de-tuning and more likely to improve fuel mileage under load.


The block is absolutely and evolution of the L series. The head is not. If this head was so good why don't L20B owners swap the Z series head onto them? Because they have nowhere near the power potential, make that breathing ability, of the L head design. No amount of porting can correct this... I won't say design flaw. This motor was not designed to flow where it wasn't intended to run. What it does do, it does very well.

But by the the 1980s nissan works performance (the factory) decided this was a superior head....


It was a superior emissions reducing head design yes but hardly what they would prefer to have in their cars for racing. It probably raced against the comparable Toyota/Honda/whatever cars that had to run similar emissions motors. But this is what they had to work with in the '80s

and used it for racing along with the DOHC LZ heads from JDM formula 3 for turbo apps, the 8v L heads were obsolete old school by then, look up George fury's Z18ET stanza and you might find some picks of that motor (no L head but it did have 8 plug distributor) I could email you a pick if you can post it.


You make it sound like the Z series was a race engine (though it was raced) when in the same sentence as the DOHC LZ and JDM formula 3 turbo. It was simply the stock motor that was in the cars that were raced or simply what they had to work with at the time.

PS does that mean you HAVE seen a L20B 54mm crank and it has 5 bolts?


What I meant was that in my experience all 6 bolt crank 4 cylinder L20B and Z motors had the 60mm main bearings. Shop manuals like Chiltons and Haynes can only copy the factory manual mistakes. I've measured L20Bs, Z20/22 and Z24 cranks and all were 60mm. I have never heard otherwise. There were some non production full race L16s with 6 bolt cranks but this isn't the same.


BTW I have a Z24 in my 3,600 lb 620. I selected it because it has superior pulling ability low speed torque. I have two 4 plug Z20 heads, two Z22 8 plug and one or two Z24 heads, and have ported two of them and yes they are poorly machined with flashing and runner seams, but nothing that would hamper low speed flow. I have no intensions or illusions of increasing performance with it. It runs great and I really like it.

Everything aside the Z series is perfect for a turbo application with it's hemi combustion chamber, cross flow, and dual plugs. All contribute to a cooler running head that is detonation resistant... a must for a turbo motor. The turbo does all the breathing work.

I think I mentioned on this before but Jason Gray mentions measuring the NAPS head combustion chamber and getting 45ccs. This, I believe, is because he was measuring a Z20S head from an A-10 and also used on the '84-'86 720 Mileage Option motor. They are 45cc or close to that. The Z20E, Z22S and Z24 are 57cc. Big difference here and I don't think he would have made this mistake.
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#20 The Stig

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Posted 30 May 2010 - 10:43 AM

Wow! This is getting beyond the point I was trying to make, I was really just trying to use all of what I said as examples to counter the opinion that the Z crossflow head was designed to reduce emmisions, as it wasnt. And that NAPS refers to a package of emmisions garbage applied to several diferent Nissan engines, rather than the Z head itself. The Z motor wasn't designed as a race motor, it was designed FROM one (YB26= L26 bottom with crossflow Z style head). I also made refrences to other similar engines in the Nissan family to show that the Nissan crossflow head is as old as the Nissan L head and was not a new "fresh sheet design". I have NO illusions about the potential/actual performance of either the L or Z heads. I was also comparing stock heads no SSS no FIA no JDM W53. When you mention flow your pointing to 4000 RPM and higher, not alot of that on the street, just on the track.
I have driven both a A10 with a DGV carb L20B and a S110 with a Z20E and I believe the S110 to be heavier, and it was faster both in acceleration and passing under load. (and the bone stock KA24E in my D21 would dust em both) I agree with you the Z head is less desirable for racing/high flow modified street engines.

So I would say my answer to your question on why don't L20s get swapped for Z20s is three reasons;
1. They actually WILL install a bigger cam and valves and better induction on the L motor (likley for racing as that stuff is now getting rare and expensive)
2. They have emissions issues that prohibit a swap, but that would kill option 1 as well
3. They read on the internet that the Z head is a POS, and everything on the internet is true, isn't it?
so they toodle around in their carby L20 or Z20/22/24 without considering the cheap and bolt on worldm of possibilities described at the top of this thread, using the Z head they have, and a Z24 or Z22 block and L/Z20 crank (and I recommend EFI) to make their motor WAY better. Which is the only reason I spoke up in the first place.:blink:

and I would rather have a Z20 any day over an L16 or J13, or even R16, but I would not bother with a L20 or Z series motor any more either. FJ20 SR20 KA24DE or even a CA18DE are all better options.

And I was trying to find that crank misprint in the manual and saw on page EM-23 of my 1980 200SX FSM it lists the main journal dia. as 54.942-54.955
I too have never found a crank from a Z series to be under 59mm, so the misprint is very common as this is the 2nd time I have found it in FACTORY literature.