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