[V8Vairs] Oops... Shoulda changed subject line to Project Update...

[DEvans at csu.org]

I don't know if there was as much 'reasoning' behind it as there was 
desperation.  Since the drive train and the live rear axle take up all 
available space to the rear of the engine compartment, I had no choice but 
to run the headers forward.  Design is based on the numbers generated by 
the HeaderDesign program, but have been somewhat perverted due to space 
constraints.  By running the headers forward, the muffler location had to 
be under the seats.  Little ground clearance exists at that point, so the 
muffler and any attached tubing had to very thin.  The finished muffler is 
only 2-1/8" thick.  I didn't have room for a conventional round collector, 
and so had to arrange the primary pipes in a flat configuration.  That, in 
turn, forced the use of a tapered flat collector.  For ease of 
installation/removal, I flanged the primary to collector joint rather than 
the more usual post-collector flange location.  There are a few flat 
mufflers on the market, but I couldn't afford them or the extensive number 
of oval pipe bends and straights that would be needed, so I chose to build 
my own muffler.  It has internal ducting to marry the banks together like 
an X fitting.  Since the incoming and outgoing exhaust paths are parallel 
and in a counterflow arrangement, I made the gas duct walls out of 
perforated sheet so that the pressure pulses will hopefully bleed across 
and create multipath averaging of the pressure waves.  Outside radii of 
the internal ducting is solid sheet to get the gas going in the proper 
directions.  The flow path looks like it will work pretty well, but only 
time and engine start will determine if it actually does any muffling. The 
quad outlet pipes were chosen for two reasons; the pair of smaller pipes 
provides more ground clearance than a larger pipe with the same flow, and 
since the outlet size is supposed to be 50% of the total primary tube 
area, using four of the same sized pipe works exactly.  The primaries are 
1-3/4" by 36" and the collectors equivalent to 3" by 16" long.  Should be 
about right for the warmed over 500.  The exhaust outlets dump just in 
front of the rear wheels.

The engine cover and air cleaner housing is designed to pull fresh air 
from the Corvair cooling air plenum though a 3" by 16" duct which rides on 
an aluminium plate bolted to the carb.  That plate also served as the base 
for the air cleaner element and so obviously must float with the engine. 
The engine cover has a lip inside to attach an air seal to isolate engine 
compartment air, and bubbles up to clear the element.  The transverse 
bulkhead and the three part engine cover also serve as the firewall. 
Strange what we get ourselves into, isn't it?

Doug Evans
'67 Coupe with very little remaining stock





"Rick & Janet Norris" 
Sent by: v8vairs-bounces at corvair.org
03/28/2005 04:32 PM
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Re: [V8Vairs] Front Wheel Size Capability...






Doug,
That's a neat exhaust system. What's the reasoning behind it?
Rick Norris

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