open headers vs. full exhaust ? UPDATED new best
#803319
09/16/10 07:55 PM
09/16/10 07:55 PM
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Joined: Oct 2003
Posts: 4,013 South Park, Pa.
68LAR
OP
master
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OP
master
Joined: Oct 2003
Posts: 4,013
South Park, Pa.
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For the first time in about 15-20 years, I plan on running this Saturday at the PID reunion at Pittsburgh Raceway with no exhaust system, just headers. The only reason that I'm doing this is for my brother. He has always wanted to see me run with open headers and I don't get to see him much. This weekend he is coming in from out of town to watch me race. I'm thinking that the performance won't change much, just the noise level. What do you guys think?
Last edited by 68LAR; 09/21/10 12:37 PM.
4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
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Re: open headers vs. full exhaust ?
[Re: 68LAR]
#803320
09/16/10 07:58 PM
09/16/10 07:58 PM
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Joined: Feb 2007
Posts: 6,295 U.S.
moparniac
master
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master
Joined: Feb 2007
Posts: 6,295
U.S.
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whats the whole exhaust setup right now...
Mopar Performance
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Re: open headers vs. full exhaust ?
[Re: 68LAR]
#803323
09/16/10 08:36 PM
09/16/10 08:36 PM
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Joined: Jan 2003
Posts: 302 Casa Grande,Arizona
DennisJ
super street
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super street
Joined: Jan 2003
Posts: 302
Casa Grande,Arizona
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If you don't jet your carb a couple of steps richer,you will probably be a couple of 10ths slower.
Dennis Jokela
I started out with nothing,and I still have most of it.
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Re: open headers vs. full exhaust ?
[Re: Mr.Yuck]
#803324
09/16/10 08:37 PM
09/16/10 08:37 PM
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Joined: Jan 2003
Posts: 4,247 Newfoundland
codfish
master
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master
Joined: Jan 2003
Posts: 4,247
Newfoundland
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Quote:
you'll pick up 3-4 tenths
You're kidding right?
codfish
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Re: open headers vs. full exhaust ?
[Re: codfish]
#803327
09/16/10 10:38 PM
09/16/10 10:38 PM
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Joined: Jan 2003
Posts: 24,562 Brookeville, Md
Mr.Yuck
Not enough dumb comments...yet
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Not enough dumb comments...yet
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
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Quote:
Quote:
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.
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Re: open headers vs. full exhaust ?
[Re: DJVCuda]
#803329
09/16/10 10:57 PM
09/16/10 10:57 PM
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Joined: May 2009
Posts: 511 Temperance, MI
68 HEMI GTS
mopar
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mopar
Joined: May 2009
Posts: 511
Temperance, MI
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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.
68 Dart GTS "HEMI" 10.30 @ 131 pump gas street car 3780# 69 Roadrunner 511 six pack 10.92 drive to track street car
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Re: open headers vs. full exhaust ?
[Re: 68 HEMI GTS]
#803330
09/17/10 01:52 AM
09/17/10 01:52 AM
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Joined: Oct 2003
Posts: 4,013 South Park, Pa.
68LAR
OP
master
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OP
master
Joined: Oct 2003
Posts: 4,013
South Park, Pa.
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So, jet up primary or secondary or both?????
4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
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Re: open headers vs. full exhaust ?
[Re: 68LAR]
#803331
09/17/10 02:15 AM
09/17/10 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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Quote:
So, jet up primary or secondary or both?????
Both, but remember, if you don't run "extentions" you'll more then likely (most definitly) loose 60ft. times, there goes your whole purpose of any gain , sure un-corked exhaust = HP, 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)
Start off with the jets you have now, make a pass, then jet up 2&2.
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Re: open headers vs. full exhaust ?
[Re: 68LAR]
#803333
09/17/10 03:41 AM
09/17/10 03:41 AM
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Joined: Aug 2003
Posts: 43,230 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,230
Bend,OR USA
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I had one car(1969 Dart 440, 727, 3.91 and slicks) with Hooker 2 inch fenderwell headers to 2.5 turbo muffs and side pipes exiting in front of the rear wheels. It ran 12.23 ET at 109.7 MPH corked up, I remove the muffs and pipes (9 or 12 lbs each side maybe (no other changes) and the car ran 11.39 at 117.8 MPH My Duster has a full three inch exhaust to the 3 inch x 14 long Magnaflows mounted at the rear bumper, that car pick up .04 ET and .3 MPH in the 1/8 mile by removing the exhaust Those wiegh around 25 lbs per side I think I have never ran the car with the exhaust off at a 1/4 mile track, maybe some day Jet for MPH, run it the way it is on the first run(put in one or two new plugs just before that run) and then look at the new plugs at the end of the run, shut it off at the finish line if you can to get a valid read on them. make a jet change the way you think it needs to go and run it again to see if you went the right way on the jetting Go the other way if it slows down on the first jet change, I try to use two Holley jet size changes at first and then go to one size per change whenm I think I'm close Good luck,have fun and let us know your results
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: open headers vs. full exhaust ?
[Re: Mr.Yuck]
#803334
09/17/10 07:17 AM
09/17/10 07:17 AM
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Joined: Jan 2003
Posts: 4,247 Newfoundland
codfish
master
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master
Joined: Jan 2003
Posts: 4,247
Newfoundland
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Quote:
Quote:
Quote:
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.
Maybe I'll see a 10 second pass yet lol.
codfish
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Re: open headers vs. full exhaust ?
[Re: codfish]
#803335
09/17/10 07:37 AM
09/17/10 07:37 AM
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Joined: May 2004
Posts: 855 Brisbane Australia
572B1
super stock
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super stock
Joined: May 2004
Posts: 855
Brisbane Australia
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Quote:
Quote:
Quote:
Quote:
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.
Maybe I'll see a 10 second pass yet lol.
codfish
Hey codfish, what type pipes are you using, 4 into 1 or tri-y's.
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Re: open headers vs. full exhaust ?
[Re: codfish]
#803337
09/17/10 09:59 AM
09/17/10 09:59 AM
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Joined: Jan 2003
Posts: 24,562 Brookeville, Md
Mr.Yuck
Not enough dumb comments...yet
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Not enough dumb comments...yet
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
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Quote:
Quote:
Quote:
Quote:
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.
Maybe I'll see a 10 second pass yet lol.
codfish
give a whirl. It only takes a few minutes a side.
as for upping both sides of the carb, I'd think the secondary is the one you want to go up on.
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