Exhausts continue

[jmbrodsky@domain.elided]

Ken,

     I've never really understood the process of scavenging in a 
4-stroke engine.  In 2-cycle's it's easier to understand.  The 
way I saw it, the tri-y's are what 1 inch? each cyl.?  I have the 
factory manifold which outlets 2-1/4 inches.  True, you do have 
the greater volumetric efficiency at the cyl exhaust port, but 
what about the y's?  After all is said and done you reduce the 4- 
1" ports to a 2- 1/4, an increase from 3.14 sqin to 3.97 sqin.  
If the exhaust ports are larger than you actually end up with a 
reduction in size from the ports to the y.  For the best 
volumetric efficiency the outlet should increase and this is not 
the case.  Since I still have the factory manifolds, they are 
only ~20" long for the front cyls, and almost ~4" for the rears.  
The 2-1/4s: left is about 3 feet, the right comes under the trans 
and is about 6 feet.  Into the 3" the area the x-area is 7.07 
sqin.  So the restriction is nil.  How do we tell if the 
throughput of the tri-ys is greater than the factory mani's to 
3"?

     It seems like the T'all really moves, it's actually faster 
than my scout.

     I think I got a better deal since I didn't put on a cat, I 
hear the 3" cats are huge $$$.


     -Joel Brodsky

         '76 IHC Scout II 345/tf727
         '75 IHC Travelall 150 4wd 392/tf727
         '72 Chev Carryall 3dr 4wd 350/th350 sold, but not forgotten.

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Date: Tue, 03 Mar 1998 11:42 -0700 (MST)
From: Ken Farmer <Ken.Farmer@domain.elided>
Subject: Re: ihc-digest V5 #231

Joel, 

Economically, the 3" has to have the duals beat hands-down.  Even better
deal if you need to put a cat on.

However, do you think that the potential performance bennie of having
less surface area in a 3" would be greater than the benefits of scavanging
and throughput gained via some tri-y headers?

Ken Farmer
1980 Scout II - dual exhausts, stan's tri-y headers, dual cats, balance
                tube, etc
1974 Travelall 

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