RE: Manifold/header comparisons PART of the answer

["Earl H. " <earlh@xxxxxxxxxxxxxx>]

Joe,

Great post. I think this just confirms some of the conversation that has
been 
going around. While peak figures are important, the over all curve is more 
important. Same thing applies with heads. People get caught up peak flow,
you 
can have more peak flow, but less of a curve, and the head or exhaust with
the 
most flow does not give you more overall performance. It is the system with
the 
best overall curve 99% of the time. This was just a test for exhaust. Can
you believe
what the Pro Stock guys go thru? Like you said at the end, change the
intake, and it 
will change the exhaust. if you do that, now you have to do the below test
all over again. 
Change another part, start over with the test.. Way to much fun.

Earl

Steve Dulcich did an extensive header tube and collector diameter/length
test in the summer of 2006 Engine Masters Magazine.  I happen to have saved
that one.  He used a 452 Mopar wedge for the engine. This was a 12.5 to one
motor, gapless rings, 3.75" stroke, 1/2" oil pickup, 1967 915 heads with
major portwork using epoxy as well as 2.25/1.81" valves, Comp solid roller
cam
260*/258* @ .050, .650" lift, 1.6 roller rockers, 1095 CFM King Demon on
Weiand Team G intake with a tapered 1" spacer. 630 hp motor with 900  pulls.

 
 
 
Using Hooker 2 1/8" headers with both 3.5" and 4" collectors:  Low end
torque (3400) was down 28 ft lbs with the 4" diameter collectors.  Shown is
average torque/horsepower.  Stay with the 3.5".
 
3.5"  524.1/462.8
4.0"  517.8/458.3
 
 
 
Standard vs Tapered collectors:  This is tapered where the 4 primaries
enter the collector.  Average tq & hp shown.  The smaller tapered collectors
show slight gains.
 
3.5" Std: 524.1/462.8
3.5" Tpr: 526.5/464.7
4.0" Std: 517.8/458.3
4.0" Tpr: 519.7/459.7
 
 
 
Collector Extensions:  Steve put 18" collector extensions on the  Hookers.  
He used them in the full 18" length, but says that the racers  install them
and run them until a definite heat ring in the paint shows  up and the cut
them there.  Here's what he got:
 
3.5" Tpr w/o ext:   526.5/464.7
3.5" Tpr w/ext:     537.2/470.8
4.0" Tpr w/o ext:  519.7/459.7
4.0" Tpr w/ext:    531.8/467.5
 
Steve noted that the 3.5" Tapered and extended collector made an additional
73 ft lbs @ 3200, and the 4.0" Tapered and extended collector showed an
additional 90 ft lbs @ 3300.  These are good low-end gains for a 18"  piece
of pipe!
 
 
 
Primary Length:  Steve used the tapered, 3.5" collectors with the 18"  
extensions on the Hookers.  The Hookers had adjustable primaries so he ran
them with the short (38") and the long (46") lengths.  
 
38":  528.0/463.7
46":  528.2/464.1
 
The 38" primaries were slightly up throught the test, and were 50 ft lbs up
at 3500.  He says the shorter primaries have a better curve, but changing
the intake might change the curve.
 
Sorry for the long post.  


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