[alfa] single row timing chain

[White Anthony <anthony.white@xxxxxxxxxxxxxx>]

Randy and Marge wrote:
> Jack (Beck I assume) replied and ask that I post "I do not
> sell or recommend single row timing chains for 4 cyl Alfa's" that's good
> enought for me. 
 
Oddly enough, that's not enough for me.  A lot of people don't recommend a
lot of things for a lot of reasons that may or may not be apocryphal.  Jack
Beck does have more experience and reputation than most, so but I'd still
want to know what circumstances he doesn't recommend them for, and what his
reasons are.  
 
I look at 5-7 potential horsepower, and think how much it would cost to pick
up that much power through other methods on a race engine -- even, or perhaps
particularly, in a low budget race engine.  
 
Jon Pike wrote:
> We "adopted" my wife's parent's 81 380SL a while 
> ago.. and it had had this modification done to it. Strongly reccomended 
> by their mechanic, and from several other sources I encountered since, 
> it was a weak point in those engines and quite a few broke. 
 
Again this is entirely correct, but the reasons need exploring further.  Talk
to the marque specialists, and they'll note that the single row timing chains
did have a tendency to stretch, which in turn would let the timing slip,
trashing the valve train.  They'll agree that the double row timing chain was
one way to correct this problem, and was common at the time.  They'll also
note, however, that the single row timing chain is a problem at around 200k
miles, and that if you have a single chain, a much cheaper option than the
US$3000 conversion to double row is to change the single row chain every 40k
miles.  
 
 
My understanding is that the primary failure mode for timing chains is to
stretch and rattle, at which point they should be replaced.  I can't think of
ever hearing of a timing chain break (though I'm sure it has happened once,
somewhere).   
 
Unless there is another failure mode for the single row chain, the danger of
stretching seems to be able to be avoided through changing the chain with
some regularity.  Perhaps 30k miles?  Perhaps less if you have a race engine
that is regularly run hard and at high revs?  Timing chains are easy to
replace anyway -- have the parts on hand, and you could do it when you adjust
your valve clearances.     
 
For me, without more information on what the dangers might be, it seems a
worthwhile mod for a race engine which sees a lot of maintenance anyway.
Probably not worth doing on a road car that you like to drive a lot while
undertaking minimum maintenance.  
 
As for parts -- the standard Alfa double row timing chain is interchangeable
with a number of Japanese vehicles.  When I most recently changed my chain,
the box the replacement came in listed Alfa Romeo, Mitsubishi, Nissan/Datsun
and Toyota as using that particular chain.  I can't recall exact models.  It
seems fair to conclude, then, that the roller diameter, link length and
overall length is to a fairly common standard, so a good chain specialist
should be able to come up with an appropriate single row replacement. 
 
Off course, I'm not Jack Beck, don't pretend to have years of experience, and
at the moment race an Alfasud with cam belts anyway.   Take what you want.  
 
Regards,
Anthony White
Wellington, NZ
105 GTV 2000
Alfasud Sprint
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