Re: Manifold/header comparisons PART of the answer

[Joeydahook9@xxxxxxx]

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.  

[Non-text portions of this message have been removed]


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