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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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Posts: 3,999
South Park, Pa.
68LAR Offline OP
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South Park, Pa.
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
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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U.S.
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moparniac Offline
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whats the whole exhaust setup right now...


Mopar Performance
Re: open headers vs. full exhaust ? [Re: moparniac] #803321
09/16/10 08:17 PM
09/16/10 08:17 PM
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Mr.Yuck Offline
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you'll pick up 3-4 tenths


[IMG]http://i66.tinypic.com/pui5j.jpg[/IMG]
Coming soon!!!!
Re: open headers vs. full exhaust ? [Re: moparniac] #803322
09/16/10 08:32 PM
09/16/10 08:32 PM
Joined: Oct 2003
Posts: 3,999
South Park, Pa.
68LAR Offline OP
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Quote:

whats the whole exhaust setup right now...



3" stainless all the way out to the back bumper, except for the Ultra flows.


4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
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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Posts: 302
Casa Grande,Arizona
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DennisJ Offline
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Casa Grande,Arizona
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.
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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Newfoundland
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codfish Offline
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Quote:

you'll pick up 3-4 tenths




You're kidding right?

codfish

Re: open headers vs. full exhaust ? [Re: DennisJ] #803325
09/16/10 08:44 PM
09/16/10 08:44 PM
Joined: Oct 2003
Posts: 3,999
South Park, Pa.
68LAR Offline OP
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Quote:

If you don't jet your carb a couple of steps richer,you will probably be a couple of 10ths slower.





You really think I'll go lean? Like I said, I'm not looking to go faster, but it would be nice. The exhaust system flows good enough that I run a crank evac system with it.


4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
Re: open headers vs. full exhaust ? [Re: codfish] #803326
09/16/10 08:46 PM
09/16/10 08:46 PM
Joined: Jan 2007
Posts: 1,169
MI
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68shifter Offline
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MI
I did this with my brothers 69 Dart at the Martin CC. Its a warmed over 360/auto and typically ran 12.80's. At friday t&t I pulled the headers and jetted up two and ran best of 12.71 with a spinning 60ft. Saturday I put the 3" flowmasters that cut out before the rear end back on, left the jets alone and was dialing high 12.80's again. Weather was warmer but it gave me a baseline.


68' Barracuda (4 speed) 64' Savoy (4 speed) 65' Satellite (girl tranny)
Re: open headers vs. full exhaust ? [Re: codfish] #803327
09/16/10 10:38 PM
09/16/10 10:38 PM
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Mr.Yuck Offline
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Brookeville, Md
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.

Re: open headers vs. full exhaust ? [Re: Mr.Yuck] #803328
09/16/10 10:43 PM
09/16/10 10:43 PM
Joined: Aug 2003
Posts: 11,179
Atco NJ
DJVCuda Offline
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Atco NJ
I watched my EFI system fatten up my mixture when I was on the dyno from full exhaust to open headers - so yes it definitely runs lean without any changes to the fuel curve when you open the exhaust....

pull a plug when you make a pass and you will see what your engine wants

Re: open headers vs. full exhaust ? [Re: DJVCuda] #803329
09/16/10 10:57 PM
09/16/10 10:57 PM
Joined: May 2009
Posts: 511
Temperance, MI
6
68 HEMI GTS Offline
mopar
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Temperance, MI
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
Re: open headers vs. full exhaust ? [Re: 68 HEMI GTS] #803330
09/17/10 01:52 AM
09/17/10 01:52 AM
Joined: Oct 2003
Posts: 3,999
South Park, Pa.
68LAR Offline OP
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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
Re: open headers vs. full exhaust ? [Re: 68LAR] #803331
09/17/10 02:15 AM
09/17/10 02:15 AM
Joined: Feb 2005
Posts: 5,221
Branson, Mo.
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joedust451 Offline
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Branson, Mo.
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.


75 Duster, 451 10.87 @ 123.58 NA 97 Z28 6sp., 12.01 @ 115 on a 100 shot 71 Swinger. 360 magnum. 12.58 @ 105 78 cutlass, 469 BBC. 12.70 @ 108 on street tires. http://www.youtube.com/watch?v=Z2kqNmMfheU
Re: open headers vs. full exhaust ? [Re: joedust451] #803332
09/17/10 03:02 AM
09/17/10 03:02 AM
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Posts: 27,421
Balt. Md
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383man Offline
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This is my exh system on my 63 which is 3" pipes with Dyno-Max Ultra-Flow mufflers and the headers are 1-3/4 tubes. I have never uncapped it but I think I will try it the next time I go to the track which should be Oct 24'th at Capital raceway in Md for a nice NSS show. Maybe I can run a new best. Ron




Last edited by 383man; 09/17/10 03:04 AM.
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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Posts: 43,007
Bend,OR USA
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Cab_Burge Offline
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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)
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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Newfoundland
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codfish Offline
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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

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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Posts: 851
Brisbane Australia
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572B1 Offline
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Brisbane Australia
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.

Re: open headers vs. full exhaust ? [Re: 572B1] #803336
09/17/10 09:16 AM
09/17/10 09:16 AM
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Newfoundland
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codfish Offline
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TTI under chassis 2" headers with 3.5" collectors, 3" X-pipe kit and 3" Ultra Flows.

codfish

Re: open headers vs. full exhaust ? [Re: codfish] #803337
09/17/10 09:59 AM
09/17/10 09:59 AM
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Mr.Yuck Offline
Not enough dumb comments...yet
Mr.Yuck  Offline
Not enough dumb comments...yet

Joined: Jan 2003
Posts: 24,562
Brookeville, Md
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.

Re: open headers vs. full exhaust ? [Re: 68LAR] #803338
09/17/10 10:03 AM
09/17/10 10:03 AM
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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BradH Offline
Taking time off to work on my car
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Val-haul-ass... eventually
The last time I bothered to uncap my headers the car slowed down because the lack of any effective collector length killed the torque and the 60-ft. I don't even bother running it any other way than with the full exhaust now and figure "it is what it is" w/ respect to performance.

And I HATE loud cars that can't back up the extra noise level.

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