E.T. Gains from open headers

What kind of gains in E.T. and speed would unhooking the exhaust pipes from the headers could I see at the track? I run TTI headers with a 3" collector into 2 1/4 pipes through Ultra Flows and out to the chrome tips. Also would header extensions be beneficial? It runs great with the setup, just wondering if it was worth the effort to unhook them. Motor is a 416 stroker. Thanks!! Greg

You will most likely go slower with open headers if you do not add collector length. I start at 12 inches and go longer til it slows down.

All you preverts can just let that go.


I learned this years ago when guys picked up with mufflers. They were adding collectors length. Most collectors are too short IMO.

I think you will pick up a lot !!! I would bet 4 tenths with that 21/4 pipe gone.maybe more.

2-3 tenths very likely. Maybe more. Adding a tailpipe to the collector would help also, but it sounds like you are just unbolting the exhaust, not removing it. Probably not enough room underneath to add tailpipes.

I had a 408 stroker running in the 11.20s with tti headers. I had 3 inch dual exhaust with 40 series flow masters iirc that dumped before the rear axle. Much less restrictive then yours. I gained 5 rwhp by unbolting it.

Agreed.

My Duster picked up 2-3 tenths (13.0 car) and my GTX (11 sec car) would pick up 4 with crappy flowmaster muffler system.

A friend of mine had a 383 satellite that ran 12.8 with 2-1/4 pipes, dropped .4 just unbolting the pipes, didn't even take them off.
Mick

It will probally pick up enough to make you wonder why it did that much I had a 440 motor in a 1969 Dart with Hooker fenderwell headers with 3.5 inch collectors running into 2.5 inch head pipes about 20 inche long running into a old set of 2.5 Turbo muffllers and then out with 2.5 inch side tail pipes that ended in front of the rear tires. That car ran a best 12.23 at 109.5 MPH with the exhaust system on at LACR 1/4 mie track, it ran 11.39 at 117.& MPH with it removed My next pump gas street car ran a best of 7.01 at 95.3 MPH in the 1/8 mile with a 3 inch system with 3x14 inch oval Magnaflows straight through mufflers, I removed that system, it went all the way to the back bumper, and the car picked up to 6.98 at 95.5 MPH
Bottom line is all of our cars don't react and get the exact same results with the same changes
Let us know your results please, more data to the data base

My guess is it will pick up WAY less than most here are saying. Less than a tenth.

On my old 3" w/ flowmaster 40's WAY less then a .10 second gain. Wasn't worth the hassle to unbolt them. Plus how it is on the street, is how I race it at the track

Bet you'd see bigger gains on a supercharged/turbocharged setups.

Next weekend is the Mopar race at Milan so I think I will unbolt it and see what it does and report back here. I am with you Darth that how it is on the street is how its raced but with more power the curiosity is killen me

3" into 2.25" is the problem area, I think 2 tenths.

Add a collector extension.. for a total length of 16"..
dump the exhaust and those muffs.. they have high back
pressure... you should pick up a couple of tenths anyways..
maybe more but you will need to re tune the carb

Depends mainly on how restrictive the system is and how optimized the A/R ratio is at WOT pulling through the load.

Over 30+ years I've seen >1/2 second on a super-restrictive system, and then I've seen only a couple hundreths, and depending on suspension and traction it may possibly/mainly show up only as MPH.

Going from a small but free flowing dual 2 1/4 to open headers I'd expect .08 to .2, tough to tell but you'll improve. May want to bring some jets +2 to +6 from where your at now.

My 360 makes 450-500hp on a good day. I have a 3" system to ultra flow mufflers and it goes out 2.5" tailpipes. It's all muffler shop bent stuff. I put some exhaust cutouts about 12" back and with them open it is .1 and 1mph faster.

When I went from flow masters to ultra flows it picked up 2mph roughly, I changed some other stuff also so it's hard to tell but they for sure helped. I also quit getting a sooty intake after I lost the flow masters

I say you will pick 3 tenths. Get that rollbar in big money!

I kinda have to outright laugh at some of these replies. 3 or 4 tenths is like 50 or 60 horsepower on this engine( or more). Just don't see it at all. That's like going from stock J heads to Eddie heads. I picked up 4 tenths doing that years ago on a 340 with boltons. Gaining the same by ditching exhaust.... Lol

2.25" AND flowmasters tells me he will see more than my .1 but .5 eh I dunno.

On my chasis dyno we see from 3hp to max 15-18 hp gain with cutouts open. depending on the placement of them sometimes it was a pay cut!!!

alot depends on the camshaft...lots of overlap hate exhaust.ive seen anywhere from 2tenths up to almost a full second on the same car same exhaust system just a cam swap.

That makes sense. Even at the upper end( 15/18 horse) that's likely a tenth. That's a long, long, long way from 3 or 4 tenths, which would be like I said, 50 or 60 horsepower.
The op's car runs 11.20's, so a pretty mild 416 motor.
I have actually unbolted exhaust before on a 416 and not seen a thing, except perhaps maybe the weight of what was taken off the car.
Some cars even like exhaust, it can create a little more bottom end.

unbolted exhaust from open headers gained .10 in the 1/8th mile. Exhaust was 2 1/2 ish flowmasters with Hpipe. Mild 440 in a 70 b body.

Hopefully you can un-hook it at the next race so you'll know for sure, but with it un-hooked it may need more or less jetting too so you'd have to play around with it but at least you'll have a general idea just by un-hooking the exhaust.

I've mentioned this many times here but the system on my 9 second DartSport didn't slow the car down at all and was fairly quiet on the street.
It was a 3.5" Doug's X-pipe with 3.5" Magnaflow stainless race mufflers, and turnouts to the side of the car in front of the rear wheels. Car ran 9.90 on the same day with and w/o the 75 pound exhaust system, and I did do jetting that day.

Yes I agree, take some jets. Look forward to the results.

Yea, I figure to up the jets at least +2> I think the first run I will just unhook the exhaust then do a jet change so everything will be the same on the first hit. Hey Don the motor isnt really mild but its being held back keeping it mostly streetable,like 727 trans, 3.73 gears, full interior, big 11" stock style brakes, and weighing 3100#. Unfortunately all info I got on the cam is its a 620" lift comp cam. Thanks for all your input and we shall see!!

Haha. I wasn't trying to pick on ya bro.

My old 416 was mild, car weighed 3350, full interior including back seat, stock hood, all steel except glass bumpers, had just mildly ported eddies, 727, ran 10.70's with muffs on it. Drove it 70 miles round trip to race it on several occasions at 131. So that's why I say mild. My cam was 260/266 flat tappet, about 620 lift with 1.6 rockers. Dinky 1 5/8 to 1 3/4 TTI headers.

Oh I know you werent picking on me, I just wanted to give you a little info on it since I havent seen you in quite a while. I like the way it runs but I figure there might be a lot more in it with a few mods to the car I dont need to do to enjoy it.

Btw, that's a beauty. Nice car.

From my last trip to the track- Car went from manifolds to headers and picked up 6 tenths alone with no other changes and then I started tweaking the carb and shift points. Just dropping the exhaust the car went from 13.3 at 101 to 13.1 at 104 with no other changes. Between installing headers, tweaking the car and dropping the exhaust a calculated 70+ hp increase.

All documented, at the track same day with video.

https://board.moparts.org/ubbthreads/ubbt...y-feelings.html

Car has Doug's headers now and a mandrel bent 2.5" system, no H-pipe and average turbo style mufflers.

-----------------------------------------------------------------

Car ripped off a mid 13 like it was nothing. Car was left in drive just like 2 weeks ago.

13.49 ET-100.19 MPH-1.93 ST

Third pass- Jetted the primaries one step richer, manually shifted 400 rpm higher.

13.31 ET-101.42 MPH-1.91 ST

Fourth pass- This was a lost pass that got my teeth on edge, best short time of the day! When I was shifting from second to third I missed and went into neutral! I instantly lifted, popped the shifter into third, waited for the trans to engage and mashed the gas again.

13.30 ET-100.09 MPH-1.86 ST

Fifth pass- I know I was running out of time (3:11PM) and the track was packed so I decided to go for broke and drop the exhaust. Dare I hope there was a 12 second pass lurking? The prior pass with a 1.86 ST should have been a 13.0-13.1. The track was a little slippery again and I could hear the slicks spin on the launch.

13.12 ET-104.14 MPH-1.95 ST

Sixth pass- I lowered the slick pressure in an attempt to get some more hook which is why I lost some MPH. Dropped from 12 PSI to 9 PSI. Best ET of the day (4:37 PM)

13.08 ET-103.4 MPH-1.88 ST

Seventh pass- Last of the day.

13.10 ET-103.5 MPH-1.88 ST

I could have made another pass but felt I didn't have anything left in my bag of tricks to get that last tenth. The car is over a full second quicker than its last outing. If I had a set of 4:10's out back the car would be flying in the 12's all day.

what? Maybe if he had a good 3" system. I'd guess you'd pick up 3 tenths with open headers. I ran 2.5-3 tenths faster with open in a mild 440 w/ 2.5 exhaust and Dynomax muffs. In my 440-6 Charger I only picked up 1.5 because I had a good 3" system.

Ok, some results are in. Just unhooking the exhaust the first pass was 11.12, second was 11.11, then third was 11.06. It ran a couple 11.10's a 11.09 and an 11.07 so it picked up .22 overall, had a new best 60' at 1.478 and a new best speed at 120.39-old best 60' was 1.53 and speed was 118.76. I didnt have time to remove the air cleaner hardly as I double entered in classes and they were calling the next class while I was still in the staging lanes, so no jet changes but I think it could hit a 10.90ish with tuning. Im happy with the results as it is really a street car. I did get warned the first round of elininations by the starter before I pre-staged that If I was going to dial below the 11.50 rule I would need better belts, a jacket, and a roll bar but they would let me run today!! Thanks for all your opinions and suggestions!! Greg

Great results, sounds like a fun car for sure!

Nice Gains. I heard they actually did track prep today.
Doug

pretty dang good, some tuning should get it faster.

Nice. Ron

Congrats, i thought you'd pick at least .2 up.
Mick

Track prep was pretty good this time Doug. I did have 1 pass in the left lane where it spun and I lost .2 in the 60' which resulted in a 11.29 run. Go figure having to pedal a small tire 11 second car??

Congrats... pretty much what I figured.. you'll
do better with tuning

I thought a tenth. So I was wrong