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DRR Trophy
posted
I’m getting a new set of headers built in the next few days and wanting to get some opinions on primary and collector diameters. It’s a small block Chevy 415incher Brodix 227 heads with chad speiers port job on methanol. 2800 lb car and shifting at 7000rpm with 5500 converter. I’m bent on tube size but was thinking 1 7/8 into 3.5 or either a 1 3/4 stepped to 1 7/8 . Any thoughts?


josh singleton
 
Posts: 18 | Location: pikeville tn | Registered: December 20, 2015Reply With QuoteReport This Post
DRR All Star
Picture of 1320racer
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1 3/4 x 3 collector if it were mine, same size header on my former 700+HP 468.


O'IT!

Offering 1st hand experience and advice based on track proven performance, on the web since 1998.

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Posts: 9198 | Location: NJ | Registered: August 20, 2000Reply With QuoteReport This Post
DRR Pro
Picture of Canted Valve
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Reher-Morrison: 23*,427", 725 Hp/585 ft. lb., 5800 stall. Headers: 1-3/4” to 1-7/8” Primary tubes (30-32” long) w/3-1/2” collector (12” long). You decide what's right for you.



Illegitimi non carborundum
 
Posts: 1274 | Location: OKC, OK | Registered: February 15, 2008Reply With QuoteReport This Post
DRR Trophy
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Fwiw, my 400 inch sbc saw zero performance improvements when I changed my rusted thru 1 3/4 headders for 1 7/8. No mph ,no et.
 
Posts: 104 | Location: Going to or returning from the chipmine. | Registered: July 01, 2011Reply With QuoteReport This Post
DRR S/Pro
Picture of The Bozman
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1 3/4 to a 3 or 3.5 collector, the length will be different depending on which you choose


Keeping the Socialists and NEO-LIBERALS at bay with FACTS one post at a time !!!

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Posts: 2790 | Location: Rockwall, Texas | Registered: June 25, 2002Reply With QuoteReport This Post
DRR Trophy
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Thanks Guys , I appreciate the input. I ran this engine before with 1 3/4 x 3. In a 3000lb car that ran 6.0s consistently. I alway thought more size would help but maybe I was dead on.


josh singleton
 
Posts: 18 | Location: pikeville tn | Registered: December 20, 2015Reply With QuoteReport This Post
DRR Sportsman
Picture of KWig
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I still go with the exhaust valve size theory, when it’s NA. 5% larger than the exhaust valve, the you can step it.
 
Posts: 728 | Location: Cumming Ga | Registered: January 07, 2007Reply With QuoteReport This Post
DRR Trophy
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What is the affect if you are way over size?
 
Posts: 40 | Location: MN | Registered: August 02, 2005Reply With QuoteReport This Post
DRR Trophy
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1 3/4
 
Posts: 61 | Location: cincinnati | Registered: November 08, 2006Reply With QuoteReport This Post
DRR Sportsman
Picture of Tom Reyer
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I have 2" on my 355, lol.


72 Nova "Hooptie"
 
Posts: 667 | Location: Hanover, MD | Registered: June 20, 2016Reply With QuoteReport This Post



DRR Trophy
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I have always been told that too large of header will slow an engine worse than too small but I’d prefer to be as close to perfect as possible when paying for a new custom set. Now if someone has a set of Lemons that fit a Chevy 2 with a smiths race craft front clip and they want to sell them please let me know.


josh singleton
 
Posts: 18 | Location: pikeville tn | Registered: December 20, 2015Reply With QuoteReport This Post
DRR All Star
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quote:
Originally posted by Tom Reyer:
I have 2" on my 355, lol.

Way too big, definitely giving up ET.

BTW, I didn't forget about our conversation, I'll get back to you soon.


O'IT!

Offering 1st hand experience and advice based on track proven performance, on the web since 1998.

Support our President! Support our Troops! Support our economy! Buy American!!

"if you guys are so broke dyck you can't buy USA made parts you need to stay the fuc at home that's the bottomline" ----Tim McAmis

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Posts: 9198 | Location: NJ | Registered: August 20, 2000Reply With QuoteReport This Post
DRR Trophy
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23* NYES 427 SBC. Had 2" on it when I bought the S10. Changed to 1 7/8 and picked up a tenth and a half. I am seriously considering a change to 1 3/4.
 
Posts: 8 | Location: Glasgow, VA | Registered: July 19, 2016Reply With QuoteReport This Post
DRR All Star
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No surprise


O'IT!

Offering 1st hand experience and advice based on track proven performance, on the web since 1998.

Support our President! Support our Troops! Support our economy! Buy American!!

"if you guys are so broke dyck you can't buy USA made parts you need to stay the fuc at home that's the bottomline" ----Tim McAmis

< FOR SALE v





 
Posts: 9198 | Location: NJ | Registered: August 20, 2000Reply With QuoteReport This Post
DRR Sportsman
Picture of Bob Nichols
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quote:
Originally posted by DaleH:
What is the affect if you are way over size?


You will experience a loss of torque in the midrange mostly w a neglible loss at upper RPM. On a pump gas 496, a 2 3/8 primary was over a tenth slower to 330 than a 2.25. No difference downtrack. When in doubt, being conservative on tubing size will usually perform better than being large.
 
Posts: 172 | Location: Charlestown, IN U.S.A | Registered: October 30, 2000Reply With QuoteReport This Post
DRR S/Pro
Picture of wideopen231
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As with collector or zoomie debate. I think if you have carb its better to error on side of small.If running injection engine is not a sensitive to air flow velocity in or out. Not saying there are not combo where it has effect just not near as much.

Again if carb I would lean towards smaller if in doubt.


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Posts: 1062 | Location: Greensboro NC | Registered: May 24, 2011Reply With QuoteReport This Post
DRR Trophy
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Ok one other question,If I’m having fender exit headers made and the primary length is not quite as long as a standard header, what will the effect be? I assume if I go 1 3/4 x 3 it would be ok but I may sacrifice a little 60ft et with short primary and collector??


josh singleton
 
Posts: 18 | Location: pikeville tn | Registered: December 20, 2015Reply With QuoteReport This Post
DRR Sportsman
Picture of Tom Reyer
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quote:
Originally posted by 1320racer:
quote:
Originally posted by Tom Reyer:
I have 2" on my 355, lol.

Way too big, definitely giving up ET.

BTW, I didn't forget about our conversation, I'll get back to you soon.


When I put them on, I was trying to kill the hit on the starting line, plus they were a 1/4 of the price since they were used. Being a small tire (8" rim at the time) I was dealing with traction issues. Once I stepped up to a 10" rim and 10" tire, those problems went away for the most part. Even with the big 2" primary headers, my little 355 runs 6.40's with a 1.38-39 60ft. (Best ET 6.38 with a 1.37) Can't imagine it running much faster.


72 Nova "Hooptie"
 
Posts: 667 | Location: Hanover, MD | Registered: June 20, 2016Reply With QuoteReport This Post
DRR All Star
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it will


O'IT!

Offering 1st hand experience and advice based on track proven performance, on the web since 1998.

Support our President! Support our Troops! Support our economy! Buy American!!

"if you guys are so broke dyck you can't buy USA made parts you need to stay the fuc at home that's the bottomline" ----Tim McAmis

< FOR SALE v





 
Posts: 9198 | Location: NJ | Registered: August 20, 2000Reply With QuoteReport This Post
DRR Sportsman
Picture of sr4440
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quote:
Originally posted by nova421:
Ok one other question,If I’m having fender exit headers made and the primary length is not quite as long as a standard header, what will the effect be? I assume if I go 1 3/4 x 3 it would be ok but I may sacrifice a little 60ft et with short primary and collector??

it will kill some low end torque, if it was me, this is a perfect setup for some merge collectors. We have used them on a couple of cars and have had pretty good results. they are not to expensive when you get them from coan.

http://www.coneeng.com/exhaust_system_kits.html

joe


Without data, you’re just another guy with an opinion.
 
Posts: 1147 | Location: TEXAS | Registered: February 07, 2003Reply With QuoteReport This Post



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