Lach,

Good points - thanks

regards
Terry

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Lach
Sent: Friday, 14 February 2003 6:40 AM
To: [EMAIL PROTECTED]
Subject: RE: L6 Head Removal/Refitting


I agree with this but having done hundreds of these, I suggest that you
loosen the cam gear retaining bolt before you put the wedge down the
chain. Otherwise you will have wasted your time setting up the cam
timing only to have it move when you undo the cam gear. Don't forget the
two 6mm (10mm heads) bolts at the front of the head that go into the
timing case either. I have seen a head wrenched off and these two bolts
and parts of the head stayed behind!!

Lach

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]] On Behalf Of Terry Rudd
Sent: Friday, 14 February 2003 12:59 AM
To: [EMAIL PROTECTED]
Subject: RE: L6 Head Removal/Refitting


Bob,

The L6 heads are much the same deal as the L4 - I have a feeling that
this is going to turn into an essay, writing about playing with heads
invariable does. It's always a good idea to get hold of a workshop
manual for reference when doing this sort of thing for the first time
too. Good quality tools especially the tension wrench make a rough job
into a good job.

Here's a bit of a technical guide to pulling a head the correct way,
i.e. make that the way that an SOB like me was taught to do it on a L
engine 30 years ago by one of the best rally teams around.

Remove the bits and pieces to allow you to remove the rocker cover -
I'll start from there.

Remove the plugs and rotate the engine by hand to exactly TDC induction
stroke on #1 cylinder; if you go past TDC, then rotate the engine thru
700 plus degrees i.e. nearly twice more to do it again - it's not nice
to turn an OHC engine backwards, if we got caught doing it in my
learning years it was worth a swift kick up the bum accompanied with a
good verballing. When satisfied it's in the correct position, check that
valves on #1 are both closed, to be sure you can check that the valves
on #6 are open.

Note the position of the V in the timing wheel in relation to the notch
in the cam thrust plate, the V to the left of the notch is valve timing
retarded (possible stretched chain), in the centre is neutral as in
stock, and to the right indicates the timing is advanced;

Note which position (i.e. P1, P2 or P3) the dowel in the cam is
positioned on the timing wheel; factory is Pos 1, if it's anywhere else
then it's had the human touch applied to it, i.e. the valve timing has
been advanced for some reason sometime in it's past.

OK, if the cam dowel is in P1 and notch in centre of the V is as it left
the factory and indicates that the cam chain isn't stretched. You may
wish to consider using P2 when putting it back together for a small
amount of valve timing advance (4 degrees on a L4 anyway, I think the L6
is the same but I'm not absolutely certain of this). Just a word of
caution with playing with valve timing on the L6, they seem to be a lot
more sensitive to minor advance, if you don't change anything else then
things like heaps more grunt mid revs and then absolutely out of breath
at 5000 rpm can happen - it's happened to me a few times on carbie fed
L26 engines, and by returning the timing to stock it revs to 6000 + as
before - could have been just this engine, jury out on that one and I
haven't had a L6 apart in 20 years to play some more.

Check the position of the rotor i.e. is it pointing towards the front
(true #1 position) or the rear (180 degrees out) - useful to know when
you're trouble shooting.

Collecting this information before you pull it apart gives you a good
insight into getting a nicely performing L engine after a head rebuild.

Use the trusty old solid wooden chock (don't use particle board and the
like) to hold the cam tensioner in place - dimensions are 160mm long,
32mm high along one end and 45mm high along the other - thickness is
important too - around 10mm is good. A little trick to aid removal after
the wheel and chain is re-installed is to drill a hole in the top of the
45mm end so you can get the tool out - it's prone to sticking so you can
thread something fairly strong through the hole eg a leather shoe lace
is good (I nearly lifted an engine off its mounts when attempting to get
it out once). The straight edge of the chock goes in along the straight
guide i.e. passenger side;

As a bit of insurance, you can mark a link and it's position on the
timing wheel, so you know for sure you re-install it in the same place,
providing you don't change the location of the cam dowel in a different
P number. Undo the cam retaining bolt and remove the timing wheel from
the chain. It's important to keep track of where you remove bits from as
everything should be returned to where it came from - this really only
applies to head bolts, valve springs and seating washers, collets,
rockers etc. Bits like mani bolts etc are not important. Make sure that
you know the head bolt removal sequence, on most engines it is the
reverse of the tightening sequence as shown on the VRS set.

Once you've removed the head then remove each valve, (remember to label
or use some method to identify where it belongs), check the valves
aren't bent i.e. slide in the guides easily, change the valve guides
(always with an old L head as the guides wear), de-coke the valves,
check the seats for blow by and correct as required, check that the head
is flat and serviceable, by serviceable L series head has all of the
letters in "NISSAN" along the lower edge towards the front cylinder
visible, if it's on the limit and you need to shave it further to true,
then it's head saver time, or better you will need to source another
head.

Don't forget check that the cam dowel is tight in the end of the cam,
grab hold of it with a pair of pliers and check that it's tight i.e. it
wont rotate in it's hole and there's no sign of cracking around it where
it locates in the end of the camshaft. It's not usually a major problem
in a Datto L but none the less they'll grenade real bad if that dowel
comes adrift.

Re-installation is pretty much the reverse, make sure the surfaces are
as clean as you can get them. After the head is torqued down, pay
particular attention to relocating the cam timing wheel in the correct
or chosen position, as this is the part that ppl find difficult - it's
not really that hard if you follow the tear down tips. If it's not in
the correct position on an L engine it's going to show up as the engine
is turned over during the valve adjustment process. I recommend that the
crankshaft is turned over by hand thru a further 720 degrees after
completing the rocker adjustments to be sure before the starter is hit
for the first time. If you changed the dowel position to adjust the
valve timing, it is quite normal to have to rotate the cam a fraction
(around 4 degrees for each number) to refit the timing wheel.

I would only recommend that you get stuck into the inlet ports if you
have had some experience - we practiced this sort of stuff on a stuffed
as in cracked or something head to explore the limits and perfect
technique. The novice can fairly safely use a dremel and some fine wet &
dry to polish the ports, but that's all I'd do unless you are
comfortable with delving further.

if you're still reading this you will have a bit of an insight into a
routine L series head service.

Have fun with it,

regards
Terry

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Bob
Sent: Monday, 10 February 2003 9:57 PM
To: [EMAIL PROTECTED]
Subject: L6 Head Removal/Refitting


Hi All,

Ive ordered in my VRS kit and will be changing the head gasket shortly.
I have only taken a head off once before, are there any special tricks
with the L series that I should do? I looked throught the archives and
saw plenty of trouble with the chain tensioner slipping, how can I try
to avoid that? Also, is it worth cleaning up an E88 head at home with a
die grinder, is there anything worthwhile that can be achieved by a
backyarder?

Regards,
Bob



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