which exhaust manifold to use???

[tberk@mindspring.com (T Berk)]

Rob Cotner wrote:
> 
> Hey all-
> 
> I already tried searching the archives on this one.  I have an '84
> rocco with the "bad" exhaust manifold, the one with the clips.  I
> would like to replace it with a different, better flowing manifold and
> downpipe.  The archives mentioned some using diesel manifolds, and
> some using earlier rabbit manifolds.  Which is better?  My local
> salvage yard has a '75 rabbit, would the manifold and downpipe from
> that work good?  I'd like to keep my Oxygen sensor also, so I need to
> know how to fit it on.  Overall, which manifold is "best"?  Is there
> any good flowing ones that have the hole for the oxygen sensor???
> What kind of downpipe is best???
> 
> Thanks in advance to any whom reply-
> 
> Rob
> 
> 


Last 1st: Folks will tell you the spankin' bad setup is a Tectonics
Downpipe, I can't say but I believe these folks about other things.

The 75 Rabbit you are talking about is a likely candidate for the
manifold AND downpipe.  Seeing as it's an older car you may get it off
only to find a crack in the cast iron. Bad news.  This is why you
sometimes find folks talking about the A1 diesel as a better source
because it has been exposed to lower heat than the gas model.

Either way, if you get a stock m/dp setup you will find increased HP
just from bolting it on.  Look to get new exhaust manifold studs and
those cool copper nuts too, some hi-temp antisieze, and gaskets for same
as well as the manifold to downpipe fitting. Here is is where you might
want to leave well enough alone because the joining of these two often
has rusted, even broken studs.

On the bottom we're talking VW 3 bolt glory, should just tie right in.

As for the O2 sensor, I found a handy threaded port on the top of my
early style replacement, (my car came with a cracked header). I
unthreaded to plug and installed a new single wire O2, because it was up
high in the flow it gets real hot, real fast.  Only because the later
16v style puts the O2 way down low does it need the three wire heated
type.

Another good thing: the manifold's port sampled both sides for an
average, not like some DP that stick the O2 onto just one or two
cylinder's output. It is right in the middle, on the back, O2 will stick
out slightly offset.

hth,
TBerk