[alfa] re: 93 spider valve noise

["Rich Wagner" <drsavage@xxxxxxxxxxxx>]

Craig asks:

>Now the next questions for all of you mechanical types.
>
>What are the risks of clearances much lower than spec ?

In a word, dire.  If you reduce your clearances too much, the length of
time the valves stay in their seats will be reduced, making them run
hotter.  (The valves are cooled by contacting the seat.)  More of the heat
load will be transferred to the valve guide, reducing its life expectancy,
or worse, causing seizure and a sticking valve.  Reduce even farther, and
the valves won't get any cooling at all--you'll guarantee a burned exhaust
valve.  If you want to reduce your clearances by one or two thousandths, I
would say that's okay, but as an engineer, I would recommend against going
any farther than that.  It's just too risky.


>Are their any known benefits in performance to the much
>reduced clearances ?

Yes, since you're advancing the valve timing and increasing the lift,
you'll see a slight increase in power at higher RPM.  The trade-off is
reduced performance at low RPM and increased emissions...and what I wrote
above.

The valve train of your (or any) Alfa should make some noise when it's set
up correctly.  That's absolutely normal and, in fact, indicates that things
are working as they should.  I always advise prospective Alfa buyers that,
if the car they're interested in has a silent valve train, they should walk
away.  Set your car up right.  Don't set yourself up for trouble.


Rich Wagner
Montrose, CO
'82 GTV6 Balocco
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