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Motor Options for the Older Z-cars
By: NissanNiNjA on 2003-09-16 00:36:15 (MST). Views (68)
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 below.
For compression ratio calculations, take into account the cylinder head chamber
volume (see
http://web.archive.org/web/20031209014949/...om/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------------------130.2mmL16,
L24-----------------------133.0mmL13----------------------------139.9mmL20B,
Z22S, early Z22E---------145.9mm*Z20S-------------------------------??**Late
Z22E----------------------149.5mm*Z20E---------------------------152.5mmZ24,
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 boreL16, L26-------------38.1mm
/ 7.01cc dish / 83mm boreL18------------------38.1mm / 4.36cc dish / 85mm
boreL20B-----------------38.1mm / 11.36cc dish / 85mm boreL28
(early)----------38.1mm / 10.90cc dish in 280Z, early ZX.('75-'80)/ 86mm boreL28
(late)-----------38.1mm / 0.0cc Flatop in '81-'83 ZX / 86mm
boreZ20S-----------------35.56mm / ? dish / 85mm bore Z22S, early
Z22E-----35.5mm* / 9.32cc dish / 87mm boreZ22E, late-----------32.1mm **/ ? /
87mm boreZ20E-----------------31.75 / approx 13cc dish / 85mm bore (Ive also
seen flattop Z20E pistons).Z24------------------34.0mm / 15.0mm dish / 89mm
boreKA24-----------------34.0mm / 2.8cc dish / 89mm boreVG30E---------------
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?) Also- 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
Information Source: www.nissantech.com
