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Re: open headers vs. full exhaust ?
[Re: codfish]
#803339
09/17/10 10:05 AM
09/17/10 10:05 AM
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Joined: May 2004
Posts: 852
Brisbane Australia
572B1
super stock
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super stock
Joined: May 2004
Posts: 852
Brisbane Australia
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Quote:
TTI under chassis 2" headers with 3.5" collectors, 3" X-pipe kit and 3" Ultra Flows.
codfish
My brother has 2'' tri-y's with a 3'' x pipe and 3'' straight through mufflers. He has run 10.7 @ 125.5 on pump fuel with a std stroke 440 @ 3650-3700lbs. His car runs like a pig with the pipes disconected. I also have another friend with a 440 with tri-y's and its the same.
I had a 440 with 4 into 1 pipes and it responded well to open pipes.  Rob.
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Re: open headers vs. full exhaust ?
[Re: codfish]
#803340
09/17/10 10:08 AM
09/17/10 10:08 AM
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Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
BradH
Taking time off to work on my car
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Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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Quote:
TTI under chassis 2" headers with 3.5" collectors, 3" X-pipe kit and 3" Ultra Flows.
That's what I have on my Challenger, too. I don't see that particular system holding back the car's performance much, if at all.
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Re: open headers vs. full exhaust ?
[Re: joedust451]
#803341
09/17/10 10:44 AM
09/17/10 10:44 AM
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Joined: Feb 2007
Posts: 2,578
sweden
1Fast340
master
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master
Joined: Feb 2007
Posts: 2,578
sweden
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So, but you also need some back-pressure, otherwize you push the torque curve way up & there goes your 60ft., so run at least 18" extentions or install cutouts (dumps as i call them) 
cant this myth about backpreasure being good for a 4stroke engine just die?
you are right about adding lenght to the collectors to make a correct collector length but thats not for backpreasure that is to be able to take advantage of the pulses in the collectors to get all 4 pulses from the same bank tuned and work togheter, thats as good as i can explain it since my english is fairly crappy..
i dont think the threadstarter will gain much from open headers, maybe a tenth or so from the lost weight unless the exhaust has some problems (reduction in diameter in the bends or some other restriction) built into it in the first place 
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Re: open headers vs. full exhaust ?
[Re: 1Fast340]
#803342
09/17/10 11:22 AM
09/17/10 11:22 AM
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Joined: Jan 2003
Posts: 3,616
Riverside, Ca
G_bob
master
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master
Joined: Jan 2003
Posts: 3,616
Riverside, Ca
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I have a 3" system with H-pipe and spintech mufflers. I have cutouts in sort of a max wedge style, so the flow when they're capped isn't optimal. Every time I've done back to back tests, I've picked up 2-3 tenths, simply removing the plates. Now, I haven't changed the jetting since the motor was dyno'd, and it was dyno'd at sea level, 70 degrees and open exhaust. Fontana, where I usually run is 1100 ft, and DA is always 2000+, so I'm sure it's running fat anyway. I haven't worried to much about jetting as I'm not legal for 9's and short-shift it to stay in the 10.0's anyway. Best DA I've ever experienced was new year's day this year, 1700 ft. Went 9.92  Your results may vary...  
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Re: open headers vs. full exhaust ?
[Re: codfish]
#803344
09/17/10 01:52 PM
09/17/10 01:52 PM
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Joined: Jan 2003
Posts: 354
Mid-Michigan
GOREO
enthusiast
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enthusiast
Joined: Jan 2003
Posts: 354
Mid-Michigan
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Quote:
TTI under chassis 2" headers with 3.5" collectors, 3" X-pipe kit and 3" Ultra Flows.
codfish
Exact same setup I have also,TTI 2" headers,3" TTI x pipe and Ultra Flo's.will be making a few runs soon with the exhaust off,has run 10.95/121 with the exhaust earlier this month at Milan.
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Re: open headers vs. full exhaust ?
[Re: Mr.Yuck]
#803345
09/17/10 01:52 PM
09/17/10 01:52 PM
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Joined: Jan 2003
Posts: 74,970
U.S.S.A.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 74,970
U.S.S.A.
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you'll pick up 3-4 tenths
You're kidding right? 
codfish
nope. Over a stockish exhaust 3 tenths easy. My old 440 coronet w/ headers and 2.5 exhaust would pick up 3-4 tenths. There's a reason most drag cars don't have exhaust. If you jet it up 2 you can pick up et. You are NOT going to lose any. I've never seen that happen. flow = HP.
He didn't say what exhaust he had on it before you made that prediction but a 3" pipes and ultraflo's is not even remotely stockish.
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Re: open headers vs. full exhaust ?
[Re: 68LAR]
#803348
09/17/10 10:48 PM
09/17/10 10:48 PM
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Joined: Aug 2003
Posts: 11,179
Atco NJ
DJVCuda
I Live Here
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I Live Here
Joined: Aug 2003
Posts: 11,179
Atco NJ
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My game plan is to make the first time trial with no changes. I will make a change ONLY if my time slows. Seriously, I don't think I will see much of a gain in performance, just noise level. Thanks for all the suggestions, I'll update later as to the results.
pull a plug - it will be leaner then with full exhaust - so i would not be surprised if there was no gain with no jet change.
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Re: open headers vs. full exhaust ?
[Re: 68LAR]
#803353
09/19/10 12:35 AM
09/19/10 12:35 AM
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Joined: Oct 2004
Posts: 5,618
long island NY
Ari440
master
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master
Joined: Oct 2004
Posts: 5,618
long island NY
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my 18 inch collecter extentions used on a 65 454 chevelle where over 2 tenths
11.00 to 10.76
1.39 9.85 - 137 mph
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Re: open headers vs. full exhaust ? UPDATE
[Re: 68LAR]
#803354
09/19/10 02:15 AM
09/19/10 02:15 AM
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Joined: Feb 2005
Posts: 5,221
Branson, Mo.
joedust451
super gas
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super gas
Joined: Feb 2005
Posts: 5,221
Branson, Mo.
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How much gain was that, you changed the old best on your sig. picture and my memory is horrible
Old new best was set at the Mopar Nat's this year. 11.57 @ 118 and change. 3 tenths and 1 1/2 mph improvement. I never would have thought....
Why do you say 1 1/2 mph, 118 too 121 is 3 mph
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Re: open headers vs. full exhaust ?
[Re: 68 HEMI GTS]
#803357
09/19/10 09:59 AM
09/19/10 09:59 AM
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Joined: Jan 2003
Posts: 16,923
NC
440Jim
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,923
NC
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Quote:
i run 4" exhaust on my car with no tail pipes, it still picks up a tenth and a 1/2 uncorked. i think every car i've ever had picks up atleast a tenth if not more.
My car (511 CID) has 4" header collectors. I did testing with open headers, 4" collector extensions, and 4" bullet mufflers. No difference from open headers to extensions with turnouts, and only 0.02 slower with the "mufflers" with turnouts. So it depends on the exhaust system, converter/torque peak, etc. etc.
Congrats to 68LAR on his new best, uncorked!
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Re: open headers vs. full exhaust ? UPDATE
[Re: 68LAR]
#803358
09/19/10 10:34 AM
09/19/10 10:34 AM
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Joined: Feb 2005
Posts: 4,311
Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,311
Prospect, PA
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congrats. Did you do back to back runs with and without the exhaust system? FWIW, the weather difference between the Nats and PRP yesterday is worth about 0.20 sec.
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How much gain was that, you changed the old best on your sig. picture and my memory is horrible 
You are correct going off of my posted mph, but my fastest was a 120 with a 11.60et last year, so I just rounded off the difference between the two. My best ET and MPH aren't on the same pass. Kind of confusing, but that's the story of my life... 
