Ron,
This should answer it all. Thanks to Tom Walter and Alan Carmichal(sp?)
Have a new head gasket (I got mine at a reasonable price from
Nissan--good idea to buy a
spare while you're at it) and manifold gasket before you start.
[Avoid those ones that are just plain metal on one, or both, sides.
Haven't seen one in ages,
but they were difficult to seal]
Start with a cold engine, ideally one that has sat overnight.
Disconnect negative cable from battery. Remove the spark plugs.
Disconnect the temp
sender wire. Drain coolant. There should be a drain tap on the block, if
you can get it to turn
(usually VERY difficult). Remove all plumbing from head and manifold. If
possible, you may
want to remove the thermostat housing now, while you have something to
torque against.
Remove the air cleaner and carbs. Remove the starter. Disconnect the
tail pipe from the
header first, then loosen the exhaust manifold nuts/bolts, and pull the
exhaust manifold away,
which makes it easier to remove the intake manifold.
Remove valve cover. Loosen head bolts progressively in reverse (10-1) of
the pattern for
torquing them on. There is a special locking plate under the right-hand
rear rocker stud nut.
Remove the rocker arms. Remove the push rods (check the see that they
are
straight)--replace them in their same holes later.[hint: I like folding
a piece of stiff paper in the
form of a "W" with holes in the middle, then inserting the push rods one
by one in the correct
order so I do not mix them up. TW]
| 10 6 2 3 7 |
| | ---> front of car
| 9 5 1 4 8 |
|_______________________________|
When you remove the bolts, clean the threads, and check for corrosion.
If the threads are
damaged, they must be replaced. (Note that the head bolts are metric hex
head, but SAE
thread on the 67.5 and later engines). If you reuse a bolt, make sure it
goes back into the
same hole as it came from--I use an egg carton, and punch the bolts
through to keep them in
order. Note that the one holding the hoist hook is longer than the
others. Chase out the
threads.
Measure the length of each bolt as they are removed. Nine should be the
same, the tenth one
should be longer. It is fitted with an engine hoist bracket on the left
rear of the engine (#10
above). If the engine hoist bracket is missing, you should replace it
with a shorted bolt [TW]
Tap the head free by applying even taps all around the head with a SOFT
mallet--no
hammers.
After removing the head, check the gasket around the water jackets and
the chambers--you
should (if your problem was the same as mine) see where the leak was.
Now's a good time to examine the cylinder walls (Oh my god, just look at
the scoring--I
guess I'd better tear down the rest of the engine... ;-( )
Before cleaning the old gasket off from the top of the block, stuff
clean rags into the cylinders
to keep crap out of them. I use a sharp, wide putty knife--take extra
care to not score the
surface.
Also find some pipe cleaners. Make a loop in the end of one, and stuff
the straight end down
into the oil feed hole to keep stuff out of the oil passage. [TW]
After cleaning the top of the block, it is a good time to run a thread
chaser (7/16"x14tpi on
both SAE and METRIC engines) into the head bolt holes. Idea is to clean
all the crud out of
them. (You can also use an OLD bolt... cut a few groves into the threads
with a small triangle
file, and run it down in and out of the threaded hole a few times, as it
will remove the dirt.)
[TW]
Be even more careful when cleaning the old gasket off the head--the soft
aluminum scores
very easily. When clean, check the head for flatness. i use a
machinists' rule and feeler gauge.
Lay the rule on edge, diagonally. Look between them, and if you can see
any light (gaps),
then use the feeler gauge to measure the size of the gap. (Mine was
warped by .013" )
The max allowed is .0039" (0.1mm) Same for the block--check it too.
Keep the valves in place, and you can clean out the chambers on the head
with a wire wheel.
[wire wheel? Usually aluminum doesn't like that... I used that nasty
Permatex "Carbon
Remover". Use gloves, and do it out side... nasty fumes. TW]
If you want to clean off the pistons, move them to TDC, and use a sharp
piece of hardwood.
As I scrape, I use a vacuum to suck up the crap and keep it out of the
space between piston
and cylinder wall. DON'T remove the last bit of crap around the edge of
the piston--leave a
ring about 1/4" of carbon around the piston crown. DON'T remove the ring
of carbon
around the top of the cylinder wall. (If your rings are still good,
you'll want them to stay that
way.)
Installation is the reverse of removal (Don't you just hate it when the
manual says that?)
If the head was sent out for machining, I always like to make a trial
fit WITHOUT the gasket
in place. Carefully place the head on the block, and run all the bolts
down FINGER TIGHT
(this also makes sure the bolts are not too long). ROTATE THE ENGINE BY
HAND.
Everything should turn over just fine. After that, I go back and add a
little model clay to the
top of the pistons and install the rocker and pushrods. Head bolts just
snug. Rotate by hand a
few times, and remove the head and inspect the clay to make sure there
is enough valve to
piston clearance. Ya this is pretty picky, and explains why it takes me
so long to rebuild an
engine. [Tom W].
Once the clearance has been confirmed, you are on your way.
If the gasket has been wrapped in plastic with a STICKY surface it is
ready to install. If it
was just in a box, and has a non sticky surface I like to COAT it with a
light coat of "Kopper
Koat" gasket spray. Light mist is all you need. Helps seal the water and
oil passage. [TW]
Tighten the head bolts is three passes, using the pattern shown above.
MAXIMUM
HEADBOLT torque for the R16 is 50 ft-lbs. Three steps: 30 ft-lbs all
around, then increase
to 40 ft-lbs, then to the final 50 ft-lbs. The original manual
recommended DRY bolt threads...
just a little drop of oil under the bolt head is all. [TW]
Tom's recommendation: I like using a simple beam type torque wrench on
headbolts, as I can
feel the bolt tighten down as it turns. Those "torque to click" wrenches
go out of calibration,
and I hate that "snap" feeling wondering if a bolt just started to let
go.
Retorque the head after 500 miles. COLD Engine, one bolt at a time.
Mark
Baltimore
http://www.datsunroadsters.com
1968 1600
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