Re: Exhaust manifolds

[DeWitt Harrison <de@aztek-eng.com>]

At 10:54 PM 5/28/98 -0500, Doc Al wrote:
>Hi, I was looking through somw old emails and saw the dialogs about turbo
exhaust 
>manifolds.  I recently rebuilt the 5000TQ engine in my 86.  The old
manifold had 
>176000 on it and was cracked and had been welded once before.  I was
advised by my 
>frend at Carlsen to use the two piece part.  I did and am very pleased.
The unit 
>is well built and fits together nicely.  I smoothed the sharp transitions
with a 
>die grinder and used new studs.  It has bigger ports at the head and nice
inner 
>workings.  The audi engineers had to do something and they did.  Nice job.

I will definitely install this piece next time the opportunity presents
itself. (Am I
tempting fate here?)

> If some does use it, try to take the time to match the exhaust ports to
the larger
>gasket size of the newer gaskets.  This can only help.

Unfortunately, it will hurt, not help, to match the exhaust port to the EM
as you
suggest. The step in port size acts to prevent reverse flow at the exhaust port
and is absolutely necessary for best performance. There's even a name for it.
"Anti-reversion" step maybe.

>Any one else have any experience with this?  Mine is very positive and
rewarding
>when I hit the .4 Bar that this thing allows.  I am ready for a chip.
Which vendor
>is most cost effective?  I do not like having religious pistons.  

Then be sure to specify anti-conversion pistons.

DeWitt Harrison
Boulder, CO
88 5kcstq