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open headers vs. full exhaust ? UPDATED new best

Posted By: 68LAR

open headers vs. full exhaust ? UPDATED new best - 09/16/10 11:55 PM

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?
Posted By: moparniac

Re: open headers vs. full exhaust ? - 09/16/10 11:58 PM

whats the whole exhaust setup right now...
Posted By: Mr.Yuck

Re: open headers vs. full exhaust ? - 09/17/10 12:17 AM

you'll pick up 3-4 tenths
Posted By: 68LAR

Re: open headers vs. full exhaust ? - 09/17/10 12:32 AM

Quote:

whats the whole exhaust setup right now...


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

Re: open headers vs. full exhaust ? - 09/17/10 12:36 AM

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

Dennis Jokela
Posted By: codfish

Re: open headers vs. full exhaust ? - 09/17/10 12:37 AM

Quote:

you'll pick up 3-4 tenths



You're kidding right?

codfish
Posted By: 68LAR

Re: open headers vs. full exhaust ? - 09/17/10 12:44 AM

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.
Posted By: 68shifter

Re: open headers vs. full exhaust ? - 09/17/10 12:46 AM

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.
Posted By: Mr.Yuck

Re: open headers vs. full exhaust ? - 09/17/10 02:38 AM

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.
Posted By: DJVCuda

Re: open headers vs. full exhaust ? - 09/17/10 02:43 AM

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
Posted By: 68 HEMI GTS

Re: open headers vs. full exhaust ? - 09/17/10 02:57 AM

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.
Posted By: 68LAR

Re: open headers vs. full exhaust ? - 09/17/10 05:52 AM

So, jet up primary or secondary or both?????
Posted By: joedust451

Re: open headers vs. full exhaust ? - 09/17/10 06:15 AM

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.
Posted By: 383man

Re: open headers vs. full exhaust ? - 09/17/10 07:02 AM

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



Posted By: Cab_Burge

Re: open headers vs. full exhaust ? - 09/17/10 07:41 AM

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
Posted By: codfish

Re: open headers vs. full exhaust ? - 09/17/10 11:17 AM

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
Posted By: 572B1

Re: open headers vs. full exhaust ? - 09/17/10 11:37 AM

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.
Posted By: codfish

Re: open headers vs. full exhaust ? - 09/17/10 01:16 PM

TTI under chassis 2" headers with 3.5" collectors, 3" X-pipe kit and 3" Ultra Flows.

codfish
Posted By: Mr.Yuck

Re: open headers vs. full exhaust ? - 09/17/10 01:59 PM

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.
Posted By: BradH

Re: open headers vs. full exhaust ? - 09/17/10 02:03 PM

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.
Posted By: 572B1

Re: open headers vs. full exhaust ? - 09/17/10 02:05 PM

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.
Posted By: BradH

Re: open headers vs. full exhaust ? - 09/17/10 02:08 PM

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.
Posted By: 1Fast340

Re: open headers vs. full exhaust ? - 09/17/10 02:44 PM

Quote:

Quote:

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
Posted By: G_bob

Re: open headers vs. full exhaust ? - 09/17/10 03:22 PM

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...



Posted By: Paul_Fancsali

Re: open headers vs. full exhaust ? - 09/17/10 05:18 PM

With a poor dual system my caps are worth at least .25+ in the qtr when removed. I have lost power with full open headers when not jetted correctly. This past week I jetted up on a cooler night and gained another 1.5 mph That gain was killed when I tried to run colder again by changing thermo big mistake lost close to 2mph Oh well the testing continue's at the track next week
Posted By: GOREO

Re: open headers vs. full exhaust ? - 09/17/10 05:52 PM

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.
Posted By: JohnRR

Re: open headers vs. full exhaust ? - 09/17/10 05:52 PM

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.



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.
Posted By: 68LAR

Re: open headers vs. full exhaust ? - 09/17/10 05:56 PM

Quote:

i dont think the threadstarter will gain much from open headers, maybe a tenth or so from the lost weight ....



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.
A little FYI. The time in my sig was done on a 95* day with full exhaust.
Posted By: sshemi

Re: open headers vs. full exhaust ? - 09/17/10 07:25 PM

higher number jets in the PRIMARIES.
Posted By: DJVCuda

Re: open headers vs. full exhaust ? - 09/18/10 02:48 AM

Quote:


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.
Posted By: 68LAR

Re: open headers vs. full exhaust ? UPDATE - 09/19/10 03:20 AM

And the winnner is........wait for it.... wait for it..... Mr. Yuck

My car now has a new best in both ET and mph.
How's 11.28 @ 121.23 sound? The way the car ran shocked the heck out of me. I would have never thought it... By the way, I never opened the hood. The only adjustments were to tire pressure and shock settings.
Posted By: Cab_Burge

Re: open headers vs. full exhaust ? UPDATE - 09/19/10 03:32 AM

Congratulations, new best are always rewarding How much gain was that, you changed the old best on your sig. picture and my memory is horrible
Posted By: 68LAR

Re: open headers vs. full exhaust ? UPDATE - 09/19/10 03:43 AM

Quote:

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....
Posted By: 383man

Re: open headers vs. full exhaust ? UPDATE - 09/19/10 04:27 AM

Congrats on the new best. Your exh must not flow to well. I plan to uncap my car next time I go to the track. But I dont think I will pick up much as it flows pretty good. Ron
Posted By: Ari440

Re: open headers vs. full exhaust ? - 09/19/10 04:35 AM

my 18 inch collecter extentions used on a 65 454 chevelle where over 2 tenths

11.00 to 10.76
Posted By: joedust451

Re: open headers vs. full exhaust ? UPDATE - 09/19/10 06:15 AM

Quote:

Quote:

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
Posted By: sixpackgut

Re: open headers vs. full exhaust ? UPDATE - 09/19/10 07:43 AM

congrats.
Posted By: 68LAR

Re: open headers vs. full exhaust ? UPDATE - 09/19/10 01:10 PM

Quote:

Why do you say 1 1/2 mph, 118 too 121 is 3 mph


Check the time I posted. It was after a long day at the track and I was a little tired. I guess I ran out of fingers. 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...
Posted By: 440Jim

Re: open headers vs. full exhaust ? - 09/19/10 01:59 PM

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!

Attached picture 6204457-Compare_open_headers_mufflers.gif
Posted By: BSB67

Re: open headers vs. full exhaust ? UPDATE - 09/19/10 02:34 PM

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.
Posted By: Mr.Yuck

Re: open headers vs. full exhaust ? UPDATE - 09/19/10 02:39 PM

Quote:

And the winnner is........wait for it.... wait for it..... Mr. Yuck

My car now has a new best in both ET and mph.
How's 11.28 @ 121.23 sound? The way the car ran shocked the heck out of me. I would have never thought it... By the way, I never opened the hood. The only adjustments were to tire pressure and shock settings.



told ya so...lol good job. I can't wait to get mine to the track. I'd love to see thse kinds of numbers.
Posted By: gdonovan

Re: open headers vs. full exhaust ? UPDATE - 09/19/10 03:03 PM

My GTX picked up 4 tenths disconnecting the 2.5" exhaust with flowmasters from the Hooker 2" tube headers.

Exhaust was still on the car, just swung out of the way.
Posted By: dustergirl340

Re: open headers vs. full exhaust ? UPDATED - 09/19/10 03:05 PM

Congrats on the new best. Mine picks up 2-3 tenths with open headers. It likes to run lean though, so we have to fatten it up.
Posted By: TonyS451

Re: open headers vs. full exhaust ? UPDATE - 09/19/10 03:28 PM

Quote:

Quote:

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....



Congrats on the new best Larry! What were the weather conditions like compared to your previous best at the Mopar Nats? I know the weather at the Nats was brutal, so I wouldn't be suprised if your gain was more to due to better weather conditions than the open headers. IMO your exhaust system sounds perfect and really shouldn't hold you back much if any.

Btw, did you do some engine changes since last year?? Seems like you picked up a lot...Or are you just getting better at bangin the gears
Posted By: 68LAR

Re: open headers vs. full exhaust ? UPDATE - 09/19/10 04:54 PM

Quote:

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.


No, My previous best was at the Nat's @ the 11.57 on a 95* day.

Quote:

Congrats on the new best Larry! What were the weather conditions like compared to your previous best at the Mopar Nats? I know the weather at the Nats was brutal, so I wouldn't be suprised if your gain was more to due to better weather conditions than the open headers. IMO your exhaust system sounds perfect and really shouldn't hold you back much if any.

Btw, did you do some engine changes since last year?? Seems like you picked up a lot...Or are you just getting better at bangin the gears




Weather conditions were very different. Nat's it was 95* hot and humid as you know. But, as stated, I ran my best with the 11.57 @ 118 almost 119 mph. Saturday at PRP, the weather was comfortable at around 73-75*, seemed like no or little humidity.
Over the past winter I installed 1.6 rockers and an aluminum flywheel. I didn't pick up much using my old "launch and shifting" procedures. It wasn't until the UMTR race the week before the Nat's, that some stick shift racers made some suggestions to me with the launch and shift points. I started using those suggestions at the Nat's and the performance level has jumped. I can't thank all the guys with UMTR enough. Great bunch. As far a getting better at bangin' gears,.... maybe.
Posted By: oldiron

Re: open headers vs. full exhaust ? UPDATE - 09/19/10 09:08 PM

Way to go Larry
Get .15 out of the 60' & 10s street car

FWIW - pulled pipes & muffs - no change to 1/4/mph but did have a best ever 60' at PRP (but really wasn't much pipe & muffler) But I like noise - can't really tell if its loud any more though, I wonder why
Posted By: 68LAR

Re: open headers vs. full exhaust ? UPDATE - 09/19/10 10:45 PM

Quote:

can't really tell if its loud any more though, I wonder why


AAAA. What you say? Can't hear you! It's he-- when you get old an't it?????
I had a blast racing with you guys this weekend. One of the better moments in my life.
Posted By: codfish

Re: open headers vs. full exhaust ? UPDATE - 09/19/10 11:25 PM

Congrats on the new best.

Makes me want to get to the track once more this season to get a 10 second pass now

codfish
Posted By: fishy340

Re: open headers vs. full exhaust ? UPDATED - 09/20/10 01:54 PM

with x pipe 3 and 4" exhaust they have today,other then sounding like a top fuel car there is no advantage i believe..plus u have to re jet ur carb for open headers..look @ the turbo and pro charge cars w exhaust..
Posted By: Mr.Yuck

Re: open headers vs. full exhaust ? UPDATED - 09/20/10 02:13 PM

Quote:

with x pipe 3 and 4" exhaust they have today,other then sounding like a top fuel car there is no advantage i believe..plus u have to re jet ur carb for open headers..look @ the turbo and pro charge cars w exhaust..



most of those "exhuast" systems are nothing more than a way for people to say "yeah it has exhaust" They consist of big pipes and mufflers that do anything but muffle the sound and end in dumps in front of the rear wheels. Some of those things are as loud as open exhaust. A 3" complete system, including tail pipes and mufflers (that muffle) will restrict exhaust flow.
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