Re: alfetta exhaust

[mark m thornton <markmt@xxxxxxx>]

In v07.n007 Graham continues the thread on alfetta exhaust mods.  
I've been under the milano wrenching on the exhaust lately, so I 
couldn't resist tossing in some comments:

> Yes well I'm interested in any recommendations people might have
> please, as to the Alfetta exhaust. Mine has the original manifold
> and the adjacent in-line front unit (resonator, is it called?),

On the USA versions, in earlier years where no catalyst was involved, I 
thought of this forward unit as part expansion chamber and part thermal 
reactor.  On the '73 2000 I think the length was chosen to broaden, not 
to peak, the power band. I can't speak to the '77 non-cat design in 
specifics.

On the '73 there is also a center expansion chamber at the same distance 
from the front as the front is from the engine, and a rear silencer under 
the trunk.  This all has the appearance of an integrated, 
well-thought-out design.  It is not cheap.  It has a great sound.

> but all
> behind that is non-original, and apparently is standard stuff from a
> standard exhaust shop, rather than any specialist performance
> system.  I don't really know how much is to be gained if I replaced
> some or all of it with performance-orientated stuff.

Perhaps not too much.  There were contemporary articles describing dyno 
tests on various configurations.  Other than replacing earlier 
catalyst-type headers, the gains to be had from aftermarket or different 
alfa parts were not large, unless matched by a balanced combination of 
other tuning changes or head modifications.

If matched by other changes, the gains were substantial.

An opinion: standard alfa exhaust systems are not junk.  Another opinion: 
some of the standard-exhaust-shop aftermarket stuff IS junk, and gets 
welded in place, seriously impeding your maintenance and repair work.  I 
once had the heat-affected zone next to a welded repair ... one I didn't 
know about ... grow a very nasty crack ... and put an end to my track 
day.

> After all the
> engine is just a standard one (apart from the slightly warm cams),
> and as it is, it already revs perfectly happily to 6 and a half so it
> doesn't really feel like it's being restricted by the exhaust system.
> (I'm not really looking for any more than 6 and a half to be on tap,
> by the way.  This is a 90k mile old motor and not knowing its
> history I feel I should treat it with a little respect, rev-wise).

Yeeowww.  I don't recall going as high as 6500 on any of my alfas.
 
> Nonetheless, I'd be very interested in any more comments from
> Nathan and/or others on the exhaust, including :
> 
> - -  Comments on the nanifold (original Euro cast iron)..... is there
> much benefit from replacing this with a performance design?
> Is the standard Alfetta design really as poor as sometimes
> claimed?

The claims you refer to may concern the '75 to '77 catalyst/air pump type 
manifold, which was widely held to compromise performance.  The so-called 
Euro cast iron exhaust headers are what folks in the 'states pay good 
money to obtain as replacements.  IMHO they're an elegant example of how 
cast headers can be done.  Of course, none of these last forever.  They 
crack.
 
> - - Any comments about the resonator (the first in-line component
> behind the manifold)? What is its function in life, and what would
> be the pros and cons of removing it?

This sort of change could affect power band characteristics.  And also 
the exhaust note.
 
> - -  Any other comments? This motor feels pretty damn free-revving
> already. Given that, does it seem likely that I'd get much bang for
> the buck if I spent money on a free-er flowing exhaust?

Here's what I think about exhausts:  I've seen rust holes, I've seen 
cracked headers, I've seen broken welds, I've seen blown gaskets, I've 
seen 'em plugged, I've heard 'em make horrible sounds, I've seen a 
downpipe bashed halfway shut, I've seen stripped studs on the headers, 
I've seen large pieces fall off, and I've seen 'em hit the body (or the 
driveline, or the driveshafts) and make a world of trouble.  I've seen 
the wrong parts in my car.  If the exhaust system has none of these 
problems, I move on, and work on something else.

cheers,

mark m thornton
seattle washington usa

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