[alfa] Re: Zat Tensioner Vs Hydraulic in non-hydraulic mode Vs...

[George Graves <gmgraves@xxxxxxxxxxx>]

Let's get this straight. The Goggomobile of 1946 was the first engine 
to use a toothed rubber belt for timing. BUT that belt was cotton 
reinforced and prone to breakage. Luckily, the engine was of the 
"non-interference" type so the only damage done by a broken belt was 
that the motor stopped and timing lost. The concept of a reinforced 
toothed belt is accredited to a German engineer named Gilmer. I don't 
know if he was involved with Goggomobile or not, but after that, about 
the only place that Gilmer belts showed-up on cars was driving 
superchargers. The supercharger belts were steel reinforced.  The 
modern fiberglass belt, as we know it, was invented at Fiat in 1960. It 
was first used in a single overhead camshaft Fiat saloon motor of 1500 
cc in '61-62. Glas used it in their 1300 coupe engine in 1963, and 
Pontiac used it in their Firebird six-cylinder SOHC motor in 1966. Fiat 
then used it in the DOHC 124 sport motor derived from it's small saloon 
OHV motor in 1967. It's advantages (other than being cheap) is that it 
is much quieter than a chain, and while this is a plus in a family 
saloon, I think it's a negative for a sports car. After all, part of a 
classic 12-cylinder Ferrari's aural charm is that the chain sound makes 
up one of the instruments in that engine's glorious mechanical 
symphony.

Chains are good for about 70,000 miles before they should be replaced, 
and on some cars, the belt life approaches that pretty favorably. In 
those cases, using the belt is a good decision. Chain or belt, they 
have to be replaced, and certainly the cost of a belt is a lot lower 
than a chain. OTOH, it seems as if the higher the performance of the 
car, the more often the belt needs replacing. Alfa 12-valve V-6's, for 
instance, recommend a belt change interval of only 30,000 miles or 
three years whichever comes first. Some Ferraris using belts require 
that the belt be changed every 15,000 miles or 2 years, whichever comes 
first. Needless to say, on the Ferraris, at least, the decision to use 
a belt looks like a poor one. While the actual belt costs are 
reasonable (<$100 each), the labor to change them on the engines which 
used them is not. On the Alfa V-6, it's marginal. While the belt itself 
is give-away cheap (the Goodyear part is $22) and the labor to change 
it is only about $400, it would be a poor value if one didn't have to 
change the damn water pumps at about that interval anyway, in which 
case, what you end-up doing is paying for a water pump replacement and 
oh, by the way, put a new belt on that puppy while you're there (the 
belt has to come off to access the pump).


George Graves
'86 GTV-6 3.0 'S'


On Sep 21, 2004, at 2:34 PM, alfa-digest wrote:

>
> Date: Mon, 20 Sep 2004 18:33:17 -0400
> From: Joe Elliott <jee@domain.elided>
> Subject: [alfa] Re: Zat Tensioner Vs Hydraulic in non-hydraulic mode 
> Vs...
>
> I had no idea that the Goggomobil used a timing belt.  I'll be
> darned.  If you don't count microcars, I believe the timing belt made
> its debut in Glas's 1300GT of 1963.
>
> - -Joe
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