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RE: [T3] Squareback Cooling - NACA Ducts?


On 30 May 99, at 18:44, Jason Mooth wrote:

> Please don't take this the wrong way Jim.

No offense taken; I appreciate your additional info.

> I don't think that my J-pipes are "special". The exhaust system is a
> custom  1 1/2 inch full merged (long extractor) header built for Type
> 3's by S&S Headers in AZ that I put on the engine.£me under 1&2
> cylinders runs under the push rod tubes and not under the head. This is
> why it does not clear the thermostat, as much as I wish it did. A Type 1
> header will not fit on a engine with type 3 cooling due to the lack of
> clearance in the front on the engine. Many on the Type 1 headers also
> interfere with the thermostat. Mine is similiar except that the 2&4
> pipes curve outward to clear the fan housing then into the collector.
> The system has all the pipes the same length.

You're absolutely right about a type 1 header not clearing the type 3 
fan housing; sorry, my brain fade.

It sounds like the blame falls squarely on S&S who simply engineered 
their system poorly. Since the OE heat exchanger was more than 4" 
diameter, there was more than enough room to fit in both the large J-
tubes AND the thermostat, but they chose not to. Probably because 
they mostly work with users who don't know any better and leave the 
cooling stuff out anyway. They will probably excuse this by saying 
that the J-tubes protect the PR tubes this way for off-road use. A 
better solution would be to position the J-tubes appropriately and 
add two welded tabs so that the lower sheet tin could be anchored 
there, too.

Since another reason for putting the J-tubes where they did would be 
to let the cooling air from the cylinders blow on it rather than let 
it just run hot under the head. I think adding the tabs would allow 
cooling air to spill over the "sides" and cool the J-tubes, as well 
as protect the PR tubes and allow installation of the thermostat.

Just let me reiterate that it really is counterproductive to leave 
the thermostat off any street car. Race and rally vehicles are 
another matter because they don't really see that many hours of use, 
nor that many warmup cycles. Plus their engines expect to be rebuilt 
often. If you expect to get reasonable lifetime out of a street 
engine then you will want to keep all the original cooling stuff 
installed.

One of the other less understood aspects of this ^
ŻJis that the 
cooling system uses its maximum power when it is full open, so there 
is a good performance argument for leaving it intact.

Jim
-
*******************************
Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA
*******************************

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