[alfa] Re: alfa-digest V9 #1113 - valve adjustment woes

[AlfaNeely@xxxxxxx]

In a message dated 2/1/2004 4:04:02 PM Central Standard Time, 
owner-alfa-digest@domain.elided writes:
Date: Sun, 01 Feb 2004 13:37:16 -0500
From: Scott Johnson <scott@domain.elided>
Subject: [alfa] valve adjustment woes

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
--------------------------------

Scott,
    Do not worry about those valve clearances.  They are a bit tight, but 
they are fairly even.  I rather like tighter than standard clearances thinking I 
am getting a bit more lift from the cams.
    If I were really anal...  OK, I am really anal and might adjust the 
intakes.  Given that the exhausts are all at about 0.016, I would try to get the 
intakes all to about 0.014 inches.
    My theory about valve clearances is that the Alfa will run with them 
about anywhere.  I check and record the clearances.  Then I check them again about 
every third or fourth oil change.  As long as they do not change, I do not 
worry.  On an Alfa four, the clearances should never change over the life of the 
engine.  Wear to the cam followers and such is minimal.  So if any valve 
starts changing, then something else is wrong.  The engine could be sucking a 
valve.  Or you could have just gotten a bit of carbon on the valve when you 
removed the spark plugs.
    The marks on the crankshaft pulley are P = TDC, F = Static Ignition 
timing and M = Maximum Ignition timing.  On the 1750 Alfa says to run the engine to 
5000 rpm and set the timing to the M mark at that rpm.
    To check the cam timing, put the pointer on the P mark.  The cam lobes on 
either #1 or #4 cylinder will be pointing away from each other.  The 
distributor rotor will also be pointing to which ever of #1 or #4 that is at TDC at 
that point.  Actually, both 1 and 4 are at TDC, but one is at TDC at the end of 
the compression stroke and the other cylinder just completed the exhaust 
stroke.
    The crankshaft pointer is adjustable.  Before adjusting cam timing, I 
always make sure about the accuracy of the pointer.  That is pretty easy with the 
engine on a stand and the flywheel exposed.  With the engine in the car, the 
best method is to make a positive stop.  Weld a long bolt into an old spark 
plug base.  Turn the engine one way until it stops and mark that position.  Turn 
it the other way against the stop and make a mark.  TDC will be half way 
between the two marks.
    I have never measured the length of the upper timing chain to the number 
of teeth on the intermediate timing shaft.  But I do know the chain must have 
about six times as many links as the timing gear.  Put #1 on TDC.  If the link 
in the timing chain is no where to be seen, turn the engine over twice to 
bring #1 back to TDC again.  You may have to do this a third time before it 
appears.
    I always assemble the engine with the link in the chain between the cam 
sprockets.  When I tear the engine down later, it does not always seem to be at 
the same spot.  Perhaps the length of the timing chain is such that it does 
not come back to exactly the same spot every time.  Do not be too quick to 
blame some dumb previous owner.
    Now I am sitting here trying to think where I have an intermediate timing 
shaft and a timing chain.  There is a disassembled 1600 in the garage, but 
the 1600 is shorter than the 2000.  Counting the 1600 chain links will surely 
not give the same result as on your 1750.
    Now I am curious.

Ciao,
Russ Neely
Oklahoma City
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