Re: Belts or chains (which are you into????)

[Jarmanhome@domain.elided]

In AD v8#112, Tim Hancock reflected mightily on Michael Smith's previous 
comments regarding longevity of timing belts vs chains.  Now, both these 
fellows are knowlegeable and regular contributors to the 164FAQ forum, so I 
was interested in what it was everyone had to say. Myself being an old 
knuckle-buster also, having cursed both chains and belts on various marques, 
I thought I'd relate an informative conversation I had with yet another 
(extremely) knowlegeable gentleman at this year's AROC-USA Nashville 
Convention.   He'll remain nameless, but had first-hand mechanical 
information regarding a wide variety of cars over the past thirty years or 
so, and that kind of experience doesn't come from reading Chilton manuals 
whilst seated on the throne.
We talked about the various Alfas there, the ones we'd owned, the ones we'd 
like to own.  I had our 164LS there at the time, and we veered onto the 
subject of the 12 and 24 valve V6 Alfas.  I commented rather sarcastically on 
the timing belt tensioner setup, comparing it to open heart surgery, or 
something similar.  He reminded me that the Mitsu V6 has/had a similar 
procedure, that both V6s were all-alloy engines, and provision has to be made 
for the relatively huge amount of expansion between the centerline of the 
crankshaft and the cams, hence the two-step tensioner adjustment procedure.  
Still, I couldn't help but wonder why Honda can design a tensioner for its 
all-aluminum V6 (correct?), and Toyota runs its V6 cam belt around one 
sprocket per bank to simplify things (the other camshaft is gear driven from 
the rear of the head), yet Alfa continued for many years to market a design 
that demanded absolute perfection in the installation of the timing belt.   
Tim is right, there are a good number of 164 owners out there who had their 
belts done by who they thought was a competent shop, only to have the motor 
wrench to a stop when the belt slipped a short time afterward.  Our (24 
valve) car had the belt slip at idle, at the tender age of 17,000 miles, and 
it cost ARDONA a nice sum for Prestige Imports to make it right again (which, 
of course, they did).   
After having investigated the cam belt drives of quite a few V6 24-valve 
motors, as well as research into the subject at the SAE website,  I reached 
my own conclusions about the Alfa 12 and 24 valve cam belt drive systems.  
First, even though I've never owned a Milano or gtv6, I consider it a miracle 
of engineering that the belt stays on the 12 valve motors at all.  There is 
well under 90 degrees of belt contact ("arc of contact" it's called in the 
power transmission world) on the left bank cam pulley, due to the angle the 
belt takes coming up from the oil pump drive.  There's just enough 
unsupported belt span there between the two pulleys to yield a bit of belt 
whip at high load conditions, IMO.  Yikes.  Apparently, this never was as big 
an issue as the tensioners, because I am well aware of very high mileage 12 
valvers out there which have run like trains.  I know Michael would nod his 
head at that one.
Next, why the oil pump drive wasn't originally designed internal to the motor 
is absolutely beyond me...it would have been so simple, and durable.  It 
would have eliminated entirely the need for an additional belt pulley on both 
the 12 and 24 valvers, the associated complexity and directional changes the 
belt takes on.  I obtained an illustration of the belt drive system for the 
166, and noticed that Alfa had addressed the problems, finally, by relocating 
the oil pump drive and redesigning the tensioner, which altered the belt 
routing and (hopefully) improved reliability. That remains to be seen, and 
I'd welcome comments on that aspect from our other-market Alfisti with some 
familiarity of the 166 and 156 durability records to date.
Last, after having some failed parts checked out by a trusted bearing expert, 
I concluded that engine compartment heat in the 164 contributes to the 
premature failure of both the serpentine and timing belt drive components on 
both motors.  It seems to be especially true in the 24 valve cars.  Idlers 
get too hot, the grease seals deteriorate, the grease cakes up or melts away 
and then the bearing begins its downward spiral. If the cam belt drive sees 
any more frictional load than is normal, the possibility of belt skipping 
increases.  For this reason, I have consistently recommended - no, harped on- 
owners on the FAQ site to pay the greatest attention to the condition of all 
those pulleys and both tensioners (both belts) on the front end of their 
motors.   We took our car in to Prestige annually for a general checkup, and 
Bob Vollner knew exactly what to look for within the belt drives.  
Invariably, it required a pulley here and a tensioner there, even though the 
belt would be fine and well within its advisable life span.
Bottom line for you 164 owners, the smartest maintenance you can give your 
car is to always know the condition of the belt drives, and go on and spend 
the money as required to make it right.  Replace ALL idlers and tensioners 
with every belt change - no skimping.  And be certain your mechanic knows how 
to properly set up the timing belt tensioner, because it's critical.  I've 
lived with timing belt drives (FIAT 124 Spider) that were plain bulletproof, 
as tough as any chain.  But a chain will outlast a belt drive in real world 
applications, regardless of what Pirelli or Gates Rubber has to say in their 
technical assessment papers to manufacturers.  There is a reason why major 
manufacturers are once again returning to timing chains, generally, and 
forsaking synchronous belts for camshaft drives.  Longevity, durability, and 
the general perception of quality they want to engineer into their products.  
The only major advantage a belt has over a chain is accuracy of valve timing, 
and that can be addressed to a point by chain technology and manufacturing 
tolerances.
Honestly, I feel it's not a question of design simplicity, or cost, or even 
ease of maintenance.  It comes down to what happens to the vehicle (and its 
occupants) if the belt breaks, or skips a number of teeth, and what's the 
chance of that happening.  I think the answer to that one is already out 
there.

Dave Jarman
Lexington,  Kentucky
USA

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