1 3/4" vs. 2" Header Size - Page 2 - ZR-1 Net Registry Forums

XfireZ51 · 03-09-2018

Paul,

I think Marc may have documented no significant difference between 1 7/8 v the 2” primaries. If there was a difference it could be easily lost somewhere else.

Top Toy · 03-09-2018

Smaller primaries would likely be the better choice for road course racing where more time is spent in lower and mid-range rpm's and larger would be the better choice for drag racing.

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alnukem · 03-18-2018

I have a book by David Vizard, I think the SBC on a budget. It links exhaust flow to the size of the primaries. Also there are "stepped headers" that have a bigger initial size then going down to a smaller, i.e., regular size tube that sounds like it's the cats meow. I bet you could find the article on line.

Bob Eyres · 03-21-2018

Don’t “stepped headers” have the opposite, smaller initial tubes, then get bigger down line to the collector?
I have had Watsons with 2” downtubes since 1995, and they’re pretty good, (117mph trap speed on an otherwise stock engine.)

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Paul Workman · 03-21-2018

Quote:

Originally Posted by Bob Eyres

I have had Watsons with 2” downtubes since 1995, and they’re pretty good, (117mph trap speed on an otherwise stock engine.)
]

Uff-da! (as they say here in da Viking country).

Gotta love that sea level DA!

Hog · 03-21-2018

Quote:

Originally Posted by Bob Eyres

Don’t “stepped headers” have the opposite, smaller initial tubes, then get bigger down line to the collector?
I have had Watsons with 2” downtubes since 1995, and they’re pretty good, (117mph trap speed on an otherwise stock engine.)

Sent from my iPhone using ZR-1 Net Registry

Yes, you are correct. Smaller to bigger.

03-09-2018	#11
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,669	Re: 1 3/4" vs. 2" Header Size Paul, I think Marc may have documented no significant difference between 1 7/8 v the 2” primaries. If there was a difference it could be easily lost somewhere else. __________________ [SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX

03-09-2018	#12
Top Toy Join Date: Jul 2012 Location: Allentown, PA Posts: 309	Re: 1 3/4" vs. 2" Header Size Smaller primaries would likely be the better choice for road course racing where more time is spent in lower and mid-range rpm's and larger would be the better choice for drag racing. Sent from my HTC U11 using Tapatalk __________________ '95 ZR-1, aqua/gray, #167 368 LPE/Haibeck, Web cams, Stainless Works headers, B&B Fusion exhaust, 18" Fikse wheels, Alcon brakes, lowered. 491 SAE RWHP.

03-18-2018	#13
alnukem Join Date: Jan 2010 Location: Freedom Pa Posts: 275	Re: 1 3/4" vs. 2" Header Size I have a book by David Vizard, I think the SBC on a budget. It links exhaust flow to the size of the primaries. Also there are "stepped headers" that have a bigger initial size then going down to a smaller, i.e., regular size tube that sounds like it's the cats meow. I bet you could find the article on line.

03-21-2018	#14
Bob Eyres Join Date: Jul 2005 Location: Jupiter, Fl. Posts: 815	Re: 1 3/4" vs. 2" Header Size Don’t “stepped headers” have the opposite, smaller initial tubes, then get bigger down line to the collector? I have had Watsons with 2” downtubes since 1995, and they’re pretty good, (117mph trap speed on an otherwise stock engine.) Sent from my iPhone using ZR-1 Net Registry __________________ "It's about the car, not the people." 1991 ZR-1 White/Black #1236 (Owner since 1994). Stock engine with bolt-ons: Hurst shifter,"Forced Air" intake, Coplon duct, Bee Cool Radiator, Demon coils, Jeal prom, Watson headers, X pipe, 3" B&B's, Rippie flywheel, 4:10 gears, A molds, Toyo Proxes-R888's 12.06@117mph. 1.76 60ft.