XF head gasket replacement question: finding TDC and other Q's

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Chris McKenzie - 17 May 2004 08:56 GMT

Hi all, please forgive any cluelessness and feel free to let me know if
I'm about to do (or have already done) anything really stupid-

I took the head off my Falcon ('87 XF, 4.1 carburetted auto) this
weekend, and had a bit of confusion following the instructions in the
gregory's book: when I got to removing the rocker arms, it said to
rotate the crankshaft until cylinder 1 was at top dead centre of it's
compression stroke:

I figured out that I could rotate the crank by [possibly stupid thing?]
turning the power steering pump pulley by hand: this needed a fair
amount of force, but I figured this was understandable with the
cylinders copmressing the air in them. (the crank rotates freely now the
head is off)

What I don't understand is how I am supposed to tell when any particular
cylinder is at TDC, and in compression- during dismantling, I just
looked at the position of the rocker arms and took off the ones which
were fully up (I.e. no pressure on the pushrods), then rotated the crank
a half-turn and took off the rest.

I'm going to try to put it all back together next weekend after getting
the head back from being planed and getting the valves reground, and I
imagine it would be good to be able to follow the instructions.

One thing that occurs to me: If I mark a spot on the [pulley at the head
of the crankshaft, whatever it's called] where the cylinder is flush
with the top of the block, that would be TDC (I think?) Could I then
work out if it was at the top of compression by having a look at the
distributor? This won't work if the distributor goes around once per
rotation of the crankshaft.

As you might be able to tell, I haven't really messed around with
engines much: here are some other random questions-

The tops of a couple of the pistons have some dry, rust-coloured
deposits on them- not a huge amount, and it doesn't flake off with
moderate pressure. Is this a trouble sign?

I'm going to be stripping off the remains of the old gasket with CRC
gasket stripper ("side effects include additional limbs, a compulsion to
sing showtunes, and sudden death"): should I mask off the cylinders and
pistons or spray and clean them as well?

what is a good way of clearing out any debris that falls into the gap
between the pistons and the cylinder walls?

The original purpose of this job was to stop water getting into the oil:
at the moment the oil is fairly thoroughly contaminated (black and
sludgy, after only 3 months in the engine). Will a normal oil & filter
change get rid of enough of the gunk to sort this out, or do I need to
do something more?

Reply to this Message

The Raven - 18 May 2004 07:11 GMT

No.1 top dead centre means that you move the crank around till No 1 cylinder
is tdc, as for the cam shaft pulley, when i did my EA head gasket, i turned
the engine till tdc, then placed 2 tie wires around the cam chain and
sprocket, that way when ya remove the cam sprocket from the cam shaft, it
should just slide back on in reverse order with no probs. Hope this clears
ya problem up abit

Peter

> Hi all, please forgive any cluelessness and feel free to let me know if
> I'm about to do (or have already done) anything really stupid-
[quoted text clipped - 48 lines]
> change get rid of enough of the gunk to sort this out, or do I need to
> do something more?

Reply to this Message

Jason James - 20 May 2004 20:56 GMT

> Hi all, please forgive any cluelessness and feel free to let me know if
> I'm about to do (or have already done) anything really stupid-
[quoted text clipped - 4 lines]
> rotate the crankshaft until cylinder 1 was at top dead centre of it's
> compression stroke:

They indtruct this so there is no confusion when putting the engine back
to-gether, but as you have turned the engine after the head was off, it is
still an easy thing to find true TDC again for cyl number one.

> I figured out that I could rotate the crank by [possibly stupid thing?]
> turning the power steering pump pulley by hand: this needed a fair
> amount of force, but I figured this was understandable with the
> cylinders copmressing the air in them. (the crank rotates freely now the
> head is off)

That's one way. Some cars can be turned by placing a ratchet and socket on
the crank-pulley nut or by bumping the starter as long as nothing is fouling
(cam-sprocket half off or stuff like that)

> What I don't understand is how I am supposed to tell when any particular
> cylinder is at TDC, and in compression- during dismantling, I just
> looked at the position of the rocker arms and took off the ones which
> were fully up (I.e. no pressure on the pushrods), then rotated the crank
> a half-turn and took off the rest.

You have answered the question ie If your distributor is out then you will
need to place number one's two pushrods back in their holes so they are
resting on the cam lobes. Then turn the engine till you see *both* pushrods
drop to their lower height. Turn the engine 4 times until you see what I
mean. They will bob up and down and at one point where number one piston is
at TDC, they will both be down. When you see this happen, move the crank
till the piston at 1, is precisely at TDC The cam lobes are fairly flat at
their 'valves shut' position so thsi final few degrees of rotatonad will
need to be done by observing the piston.

Is important to remember the cam and distributor (dissy) turn one revolution
for every two crank revs, this is why the engine is called a 4 stroke or 4
piston excersions per two crank revs.

> I'm going to try to put it all back together next weekend after getting
> the head back from being planed and getting the valves reground, and I
[quoted text clipped - 6 lines]
> distributor? This won't work if the distributor goes around once per
> rotation of the crankshaft.

If you indeed left the dissy and the cam in place, you dont need to worry
about TDC,...but if not you can ascertain true TDC by:

noting on the periphery of the dissy upper body where number one spark-plug
lead is positioned. Make a mark with a scriber or permanent marker on the
dissy housing (so you can see it when the cap is off)

With the rotor in place on the dissy shaft (cap off) turn the engine until
the rotor is pointing at the mark you made. now within a few degrees your
engine is at TDC. To get the crabk at exactly TDC, turn the crank until
number one is exactly flush or if the head is allready on, put a piece of
straightened coat-hanger wire into the combustion-chamber via the spark-plug
hole. It will move as the piston reached true TDC.

All this mucking around only applies if you have taken out the dissy or
cam,..otherwise, just reassemble the reverse or dismantle.

Having said all that, there should also be a mark on the crank-pulley which
denotes "TDC" and degree markings. Using a torch if necessary, this should
be visible, and, should be lined up with the metal indicator on the timing
cover.If its covered in oil[dirt/grease, clean it off first.

> As you might be able to tell, I haven't really messed around with
> engines much: here are some other random questions-
>
> The tops of a couple of the pistons have some dry, rust-coloured
> deposits on them- not a huge amount, and it doesn't flake off with
> moderate pressure. Is this a trouble sign?

No, its probably due to the coolant evaporating. Just remove gently any
heavy deposits which come off easily. Avoid removing carbon from near the
piston edges with the bore. These can reduce oil-consumption, as they act as
an additional seal.

> I'm going to be stripping off the remains of the old gasket with CRC
> gasket stripper ("side effects include additional limbs, a compulsion to
> sing showtunes, and sudden death"): should I mask off the cylinders and
> pistons or spray and clean them as well?

Personally, I dont like anything getting into the bores. Id stuff rags in
there while you clean the block-face or deck.

> what is a good way of clearing out any debris that falls into the gap
> between the pistons and the cylinder walls?

There isnt any way,Just try and keep that to a minimum. Debris will blow-out
the first exhaust stroke.

> The original purpose of this job was to stop water getting into the oil:
> at the moment the oil is fairly thoroughly contaminated (black and
> sludgy, after only 3 months in the engine). Will a normal oil & filter
> change get rid of enough of the gunk to sort this out, or do I need to
> do something more?

Just change the oil/filter every 5000 ks to keep things clean.

You may need a small paint scraper to help remove the old gasket. When
reassembling, make sure the block face is as clean as you can get it.

Make sure the headbolt holes are relatively clean and the threads are oiled
with a couple of drops only. Do the same with the headbolt threads: clean
(use a wire brush) and lightly oiled. This allows the headbolts to torque-up
correctly.In fact do the same with all fasteners (nuts.bolts)

Tension the head-bolts as per the sequence in the manual. I recheck their
tension after the engine has run for an hour. To recheck, undo the headbolt
a small amount (1/4 turn), some may make a cracking sound as they come
free,then retensiononce, then reset the wrench and tension again.

Once the gasket and head are in place, lower each pushrod into their holes
(these should be matched with their respective holes as should the
rockers,..they should auto-centre themselves into the cam-followers
(hydaulic lifters). Tighten down the rockers after you have made sure they
have their respective pushrod sitting correctly in their seats on each
rocker.

Use a tension wrench, the torques are in the manual. You may need to hold
the new rocker cover gasket place by coating it with a thin smear of
silastic on its upper face so it will hold in the cover groove.

Spend time cleaning the old gasket off the inlet and exhaust manifold. The
inlet needs to have a good seal to stop air-leaks. Fuel fittings require
extra care to ensure they dont leak,

Dont overtighten the rocker cover bolts otherwise the gasket may squeeze
out.

Use new hoses for the radiator etc, otherwise try and use the same clips
(they will sit in their indentations)

If the dissy is in the right possy and the carby has fuel left in its bowl
(carbies should always be left standing upright) the engine should fire-up
OK.

You really need a timing-light to check ignition timing especially if you
removed the dissy.

Look for fuel leaks (in which case, turn it off now!) coolant leaks,oil
leaks from around the head, vacuum leaks from vac hoses (make sure the brake
booster is reconnected) and exhaust leaks (make loud noises/"clacking")

Good luck!

Jason

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Chris McKenzie - 20 May 2004 21:27 GMT

Thanks heaps! That's cleared up quite a bit :)
Fortunately, I didn't need to take the distributor off, so it looks like
I shouldn't have too much trouble getting things back together. I'll let
you know how she turns out.

> > Hi all, please forgive any cluelessness and feel free to let me know if
> > I'm about to do (or have already done) anything really stupid-
[quoted text clipped - 38 lines]
> for every two crank revs, this is why the engine is called a 4 stroke or 4
> piston excersions per two crank revs.

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