Dropping a 1981-83 L-28
motor into a 240Z, with 5-speed and 3.90 differential (back)
It's important to know that externally, all '70-83 motors are identical,
only the bore and stroke are different. This is why swaps are so easy.
And not only does the extra torque from the 2.8 liter motor move the car
much more quickly, but this gives you the chance to upgrade the transmission,
differential and drivetrain to better, stronger 280Z parts. I like a 3.90
rearend, but you can leave the stock one in. Keep in mind that all 280Z
engine and drivetrain parts retrofit into the 240Z.
FIRST -the motor
Locate a '81-83 motor in a junkyard. Check the
cylinder head between the 1st and 2nd spark plugs to find the cylinder
head code. "P-79" is what you want.
- The P79 and P90 head were designed by the factory
for high-flow turbo applications and the block has flat-top pistons
instead of the dished types on '75-80 motors. This means all combustion
is confined to the high-swirl combustion chambers, which provides a more
controlled quench-and-burn than a dished piston allows. In addition, the
compression is 8.8:1 compared to the '75-80 motors which had a low 8.3:1
for good emissions. Tolerances are tighter and more consistent than earlier
motors too. And while many people argue that the '75-76 head/motors are
superior, I think that's because they quote from the "How to Modify
your Nissan OHC", by Frank Honsowetz. Had it been written in 1988
instead of 1978, I'm sure he would have recommended the P-79 instead of
the N-42 or N-47. BTW, the 170 horsepower stated for '75-78 motors is GROSS
horsepower instead of NET, which means those motors really have a NET of
135hp vs the P-79's 145hp. I can get a P-79 motor for $79.95 at my local
salvage yard, and I feel the the best ones are in automatic transmission
cars. Because of lower shifting points, the engines are probably less abused.
But make sure you get a manual transmission flywheel and the rear sandwich
plate from a manual transmission car.(see below).
- LUBE TIP: I was told by my friend the Z Doc that straight
30-weight oil should be used in L series motors. He said Mobil 1 was his
first choice, then 30 weight, then 10W-30. He felt that a straight viscosity
was more "stable" than a multi-viscosity which has more polymer
additives. In deep cold he recommended going to a 10w-30. I have heard
from more than a couple of engine rebuilders over the years that Castrol
was the best out there, so I'm running GTX 30W. Works for me...
SECOND -the transmission
- Locate a junkyard '77-79
280Z five speed tranmission. While It's ratios are "taller"
than a stock 240, coupling it with a higher-ratio
differential will provide greater acceleration and superior shifting.
But DON'T use a '80-83 5-speed with
any rear-end higher (lower numerically) than a 3.90. This trans has the
highest ratios and will slow acceleration in all gears if a 3.36, 3.55
or 3.70 is used. Just remember to get the sandwich plate from between trans
and motor on a manual trans if you use a motor from an auto trans car.
The automatic's plate only covers the top half of the trans, while the
manual's goes all the way down.
- On a junkyard 3.90 280ZX, follow the speedo cable into the side
of the trans, and remove the speedo cog and sleeve. This has a white plastic
cog (3.90) which must be exchanged for the black cog in the '77-79 (3.54)
trans to keep the speedometer correct. But, you HAVE to swap the white
cog with the black one on the older sleeve.Using the newer sleeve in the
older trans won't work, the sleeves are physically different and the newer
one won't let the cog mesh with the gear in the older trans. It's easy
to swap the cog, just drive a small pin out.
- On early 240's, you may have to cutout about 2 inches of metal
from the front edge where the shifter goes through the trans tunnel. A
5-speed sits forward slightly and the gearshift may requires more clearance.
This cutting is the price of a 5-speed trans. If this really stresses you,
install a ZX 5-speed. Supposedly they don't require cutting.
THIRD -the flywheel and clutch
- There are 2 versions of flywheels on all '75-83 motors, standard
and 2+2/turbo. About 23 lbs each.
- Standard and 2+2 clutches aren't interchangable because the bolt
holes don't match with the flywheel's.
- If you have an automatic transmission engine, make sure you get
a flywheel from a manual trans car to take the place of the auto-transmissions's
- A pilot bushing also needs to be installed in the crankshaft if
using an auto trans motor (they didn't get one).
is my 2+2 flywheel and clutch. Click on it (34K)
Measure the width of your flywheel's shiny clutch contact surface.
If it's 225m wide then you have a standard flywheel. 240mm means you have
a 2+2 version. This lets the standard 280 use a 550lb pressure plate while
the 2+2 uses a 780lb with a wider disc. So you're lucky if you have a 2+2
flywheel because you can use the stronger 2+2 clutch. But make sure the
"collar" holding the throwout bearing matches the flywheel (standard
vs 2+2) or the clutch-fork angle will be off. I had to scavange a 2+2 collar
from the junkyard because my trans came from a standard car, but my motor
had a 2+2 flywheel.. So note which flywheel the car you get the trans
from had, so you can matchup the right clutch and throwout bearing collar
(Motorsport Auto has collars for a few bucks). Remember, all motors and
throwout bearings are the same, but order the clutch and collar to match
the flywheel type your engine has, then the year transmission. EXAMPLE: "
I need a complete clutch for a 1977 280Z, 2+2" (even if you have a
FOURTH -the differential
the size difference between a R200 (left) and R180 (28k)
Get the R-200 differential out of a junkyard '81-83 NON-turbo
ZX . This will have a 3.90 ratio ('81-83 turbos had a 3.54) compared
to the 3.36 in the 240 and 3.54 in the '75-78s. Some 280ZXs had a R180
rear like the 240Z, make sure you don't get one of those by mistake. Since
the entire 280Z rear end will tranplant into a 240, offer them $100 for
the whole rear-end and see if they bite. Talk about a wolf in wolf's clothing.
Grab these parts:
- the curved rear crossmember which bolts immediately behind the bottom/rear
of the differential (early models are straight).The R-200 sits back by
about 1 1/2 inches and needs the curve. Bolts in perfectly.
- Get the "mustache bar" that bolts onto the rear differential
cover from a '75-78. Despite your budget, replace the bar's bushings with
urethane ones. I actually replaced them with new softer stock ones, which
allowed the extra torque from the 3.90 to twist the bar-ends and "thunk"
them against the floor. A waste of money. But this made me realize that
thunks are not always caused by the front mount.
- Get the R-200 halfshafts too. Be careful not to swap the halfshafts
as the shaft that slips into the differential on the passenger side is
1/4 inch longer than the driver side. I made this mistake and got 2 short
(left) ones from the junkyard. The right one wouldn't "click"
in. Had to go back to the junkyard to get a right-side one. Get the newest
ones possible (less wear obviously. Better tolerances too?)
- Get a good driveshaft from a '76-78 280Z. They are about 20 cm longer
than the 240 shaft, which will maintain drive-angle geometry. Strangely,
'75 shafts were 10mm shorter and fatter and the rear bolt pattern doesn't
fit onto a later R-200.
- The front differential crossmember from a 280Z is thicker and beefier
and should be replaced also. Of course you should replace the front differential
mount with a '75-78 version.
- My '70's differential strap sits forward by about 2 inches compared
to a 280. This let the strap sit directly over the R-200's front mount
nuts on the top, making bolt-up impossible. I had to reverse the bolts,
place the nuts on the bottom, and saw off the protruding bolt threads.
This let me raise the differential with my floor jack, and place it very
tightly against the strap. I mean it's very tight, my front
mount isn't even flexing.
FIFTH -the fuel system
Well, you need fuel at this point, but I can't help you if you
want injection. I use a set of '71 carbs and intake I got in a junkyard
280Z in 1995 for $75, which work perfectly on my '83 motor with no changes.
The carb intake will bolt right up with a '81-83 gasket, but I did have
to hold the intake in place as it's lack of real bolt holes allows it to
shift around when tightening.
- Retain the water cooling through the intake manifold and don't block
off the PCV valve hoses. I used a breather on my valve cover, but it's
important that the crankcase be vented to the intake so the motor stays
- Keep the stock fuel return rail and use an aftermarket electric
fuel pump with 3-5 psi, Higher pressure can force crud through the filter,
lower causes the bowls to run dry on heavy acceleration.
- Also run the tank vent hose to one of the carbs, otherwise the car
may reek of gas.
- Stay away from the auto-store Purolator electric pumps. Excellent
reliability I'm told, but very noisy. I tried 2 but both had a powerful
ratchetting sound, very audible over my exhaust at idle. Purolator told
me that was "normal", so back it went to Advance Auto. I'm using
a stock VW/Porsche electric fuel pump that was on my car when I bought
According to Motorsport Auto, stock 240Z carb needles will work fine
on a L28, even with a cam. I've checked my plugs and they look perfect,
nice and tan. SM series needles can be used to richen the mixture, if you
can find them.
SIXTH -the distributer
If you want to use the stock 240 distributer, you will need to
add a 280 support available from the dealer or Motorsport Auto (800-633-6331)
to raise it's height. But obviously you're doing this for performance.
- throw the obsolete, stock distributer in the closet.
- get a junkyard 280Z '77-78 single pickup electronic distributer
- convert it to a super-accurate 45,000volt Chevy HEI/MSD
Blaster coil setup. It connects easily to stock 240Z wiring
without any cutting, and provides phenominal performance. Contact Andy
Levy at email@example.com
who developed it and turned me onto this killer mod.
- If you want to use a 280Z tach with a stock distributer, connect
the tach's rev sensor directly to the negative post on the coil. If the
tach jumps around, solder a 6.8k ohm resistor inline with the sensor feed
wire. 280's use a similar resistor inline as 280 tachs apparantly need
a lower sensor-input voltage (app. 5V). But make sure you leave the stock
tach's "loop" harness connected, otherwise the car won't start.
Other than these tips, the L-28 is a direct boltup. My 1970 with P79
motor, header and 2 1/4" pipe, SU's, HEI ignition, 3.90, '78 5-speed,
and Crane cam runs consistent hand-timed 0-60's
in 6.6 seconds and a 60-80 in 3.7 seconds in third. It's torque is great
and it revs past redline without hesitation. I'm estimating about 190 horsepower.What
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