Re: [alfa] valve adjustment woes

[Michael Findlay <michael@xxxxxxxxxxxxxxxxxx>]

Hi Scott

I discovered a similar set of problems when stripping my 1750 GTV
motor. Not to worry. Everything can be put right. The first thing is to
find top dead centre (TDC) for piston 1 (closest to the radiator) If
you are confused about the marks on the crank pulley, this gives you a
starting point. Remove the sparkplugs to relieve the compression. You
can check #1 TDC with a long fine screwdriver down the plug hole. Make
sure it does not catch and bend as you turn the crank by hand  not
with the starter. When the screwdriver stops rising on the upstroke is
TDC more or less. If you know someone with a dial gauge, use that
rather than the screwdriver which is visual and approximate. The
confusing thing is that the crank is spinning at one speed and the
distributor and cams at half that. Thus the TDC has to coincide with
the firing stroke. The cam lobes on #1 should be pointing away from
each other so that  both valves are shut ready for the bang. The lobe
in the distributor will be passing the #1 terminal at that point in
time. Check the pulley and see if a mark lines up with the pointer on
the front of the timing case. So far so good. All engines fire a little
way before TDC and this varies between models. In all cases the firing
point on the crank pulley will be indicated by another mark further
around. As Alfa engines turn clockwise when viewed from the front this
mark will be to the right of the TDC mark when viewed from the top or
front. There will be other marks which relate to the degree of spark
advance set by the distributor. These don't concern you with the valve
timing issue. When the crank is at TDC two grooves cut into the front
face of each cam will line up with matching marks on the camshaft
journal cap. If you have TDC correct and these marks do not line up,
the valve timing is wrong.  You need to carefully undo the vernier pin
on the rear of the cam sprocket and move the cam until these points
line up. As long as no-one has removed the distributor and oil pump and
replaced them incorrectly you should be fine from this point on.

There are all sorts of reasons for these adjustments to be wrong
depending how the chain was replaced in the first instance. Some people
like to experiment with valve timing but valve to piston contact is
guaranteed if you get it wrong.

Good luck

Michael Findlay
1971 1750 GTV


On Monday, February 2, 2004, at 07:37 AM, Scott Johnson wrote:

> Well, now that winter seems to have settled in in earnest around here,
> I decided to check the valve clearances on the ol' 71 spider. The last
> valve adjustment was 7 years (but only ~ 25k miles) ago, so I figured
> it was probably due. Sure enough, out-of-bounds:
>
> Intake:
> .014
> .015
> .016
> .013
>
> Exhaust
> .017
> .016
> .016
> .016
>
> Worse, the main link on the cam chain (gah... whatever it's actually
> called) doesn't show up when the motor is TDC. Not *particuarly*
> surprising, since the PO of the car left out such "extras" as the lock
> tabs on the cam sprockets (discovered during the last valve
> adjustment).
>
> Also, I'm a little confused about the cam timing.. When the disty is
> pointing at #1, the pointer on the crank pulley is pointing at an "M"
> mark (I hope that means "maximo" or something... can't find my stupid
> reference book), and both valves are closed the cam lobes are nowhere
> near to pointing straight out. This may just be the way an injected
> 1750 is supposed to be, since the timing marks are awfully close at
> this point.
>
> Anyway: is there a "right" way to get the main link back to TDC where
> it's supposed to be? Does it matter that much?
>
> Finally, when I pulled the radiator out much to my surprise the bottom
> 1/3rd of the radiator shroud was just gone. It *looked* cut, but I
> wanted to ask you folks if this was stock or perhaps some sort of mod
> to make it easier to R&R. Certainly the bottom 2 nuts on the shroud
> were a bear to get at.
>
> Thanks in advance for any help you can give! :)
>
> Scott Johnson
> 71 1750 Spider
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