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Re: [Spridgets] Question

To: spridgets@autox.team.net
Subject: Re: [Spridgets] Question
From: mike rambour <lists@dinospider.com>
Date: Wed, 20 Jan 2010 14:54:24 -0800
 Ferrari in the old days also used chains, chains stretch and are a
major pain to change after they stretch, granted that is way more than
the 30,000 miles a belt lasts.   Not all Ferrari's require a motor out
to change the belts, 308, 328, Mondial's do not require the engine out,
348 I think are engine out but not sure, 355's and newer require a
engine out.  Before 308's they were chain driven.

  The belt is quieter and supposed to be less susceptible to stretch,
basically they go on and stay put until they break, so your cam timing
remains perfect (assuming perfect work to install it).  Belts also steal
less horsepower from the motor although I don't fully buy this one,
spinning a belt vs. spinning a chain would seem to be about the same to
me, but in the world of performance where every 100th of HP is desired,
belts are supposed to make a difference.  

 At least in the Ferrari world the chains require a little more periodic
maintenance then the belts because the tensioners are really from the
dark ages, I check the tension on my chains every 2 years but its a
quick/easy process, the tensioners are a bit of pain but that is
supposed to be because the motor spins at 8,500RPM and Ferrari made sure
they don't accidentally unlock and lose tension on the chains.  On the
belted Ferrari's the tensioner needs no maintenance.

 Any by the way, change those belts on the Ferrari on schedule its not a
pretty sight when the pistons make love with the valves at 8,000RPM.

        mike

On Wed, 2010-01-20 at 13:36 -0800, Kirk Hargreaves wrote:
> A Porsche has it's cams driven by an internal chain.  . the same as I think
> about it as the straight 6 Jaguar engines hailing from the 1950's (and
> possibly earlier).
> 
> Many high end cars have their cams driven by an internal chain with a
> tensioner which needs very little maintenance, if any, compared to an
> outside belt drive.
> 
> The Ferrari, and I am guessing the Lambo and other super high end cars have
> their cams driven by outboard belts . . which need to be changed out at
> around 30k miles.
> 
> With the Ferrari, I understand that it is a big process in that the engine
> has to be pulled to change out the belts.  I have read that it can cost up
> to 10k to have the dealer change out the belts in a Ferrari.
> 
> So why would Ferrari, as well as others, go with an outboard belt drive on
> their cams?
> 
> Is it because the system is lighter, gives a better response, or?  I am
> guessing that the thought is that outboard belt driven cams enhance
> performance?
> 
> Just a question that has been in my head for a while. . I never have heard
> anyone explain the theory behind the out board belt as opposed to the
> internal timing chain for driving cam shafts?
> 
> 
> Kirk
> Pushrod Drive 1275

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