Beach Bum

I typically try to share my track test results with the racers of the forum.... and I conducted another test yesterday, so here goes.

Yesterday morning I completed my true dual 3" exhaust conversion and installed new Flowtech 3" Warlock Mufflers. These Mufflers have a removable flange that allows you to run them straight through, or capped up, when capped up, the exhaust takes two 90 degree turns wtihin the muffler, when the flange is removed, they go through a straight through 3" section. Go to http://www.Holley.com and to the Flowtech product section to see them.

My previous exhaust in the past has been 1 3/4" primaries, 3" collector, into a front Y-pipe that was 3" for about 8" and then went into the non-mandrel bent 2.5" pipe and then into a single 3" pipe through a gutted cat and out non-mandrel bent 2.5" pipe and through some small muffler eliminator tips with resonators. It was a bit loud for my taste, and considering the non-mandrel bent 2.5" pipe basically went down to roughly 2 1/4" at the bends, I felt my exhaust was potentially a restriction or bottleneck.... and the thought of that irriated me, so I changed to 3" true dual exhaust with an H-pipe about 18" off the header collector, and through out the muffler eliminators and replaced with the Warlock mufflers yesterday morning.

So head to the track in the afternoon, and remove the muffler flange for straight through flow.... 1st pass was a 1.59 - 11.61 @ 116.55 with a Tag weather station reported 1740 ft DA... I was a little disappointed. In comparison 2 weeks ago with a 1200 foot DA I ran 11.63's @ 116.xx all day long. It looks like I have a few hundredths gained from the move.... but not much.

The rest of passes pretty much backed up the above... at the end of the day, I went ahead and capped up the muffler so that now the exhaust has to go through the two 90 degree turns, and ran a respectable slightly spinning 11.71 @ 115.91 mph..... looks like I'm only losing a few hp capped up.... which was pleasing considering my exhaust is much, much quieter and smoother now when its capped up. I felt the move was a good one, even though from a performance standpoint the results were a bit disappointing.

However, I do have a bit of resonance at 1700 rpm.... does anybody know how to get rid of this.... maybe an X pipe instead of my H pipe ??

My results are not conclusive yet, I feel I need to make a few trips to the dragstrip to narrow the exact results down to a # that is very precise, however it looks like even for a 383 Superram motor that makes somewhere around 440 flywheel hp that 2.5" exhaust pipe and mufflers are adequate.... oh well, win some.... lose some.

cheers,
Beach Bum

your drinking buddy

Thanks! Been thinking of a new exhaut system for my car too.

Keep us informed. :cheers: :chevy

zrracer

beach bum,
I am just starting to go down the same path. I have had an x pipe made and now I am looking into finding light pipe and mufflers. Did you find some light pipe? How much do your new mufflers weigh? Were they expensive????
My car puts out more HP than yours so I am hoping to get some gain.
TIA :D

L98Terror

Keep up the testing? Your paving the way for the rest of us :cheers:

ralph

Beach, see my email response on NMP. :seeya

Beach Bum

No the pipe I'm running is pretty darn heavy... not sure how heavy, but the whole exhaust change probably added 20-30 lbs to my already portly 3500 lb raceweight. :(

The mufflers are pretty cheap, which is why I gambled with them. I bought them from Jegs... think I paid a hair over $ 120 total to door. Not sure on their weight, but they're not light, probably 12-15 lbs each, but not sure.

Maybe a 3" exhaust will help a higher hp set-up or even a different type of set-up.... maybe a 7000 rpm 355 would benefit from the extra exhaust....dunno, didn't help me a lot though.

later
Beach

Raysur

Did you get mandrel bends? How much was the new exhaust? And where did you get it done? I've been looking for a mandrel bender in So. Cal. I found one in Bakersfield but its too far (2.2 hours away).

I'd try an x pipe. It seems to flow better. If you look at high performance exhausts systems you'll see the H pipe has been replaced with an x pipe.

BOBA VETT

How was the fit and did it effect ground clearance any?

J Z06

Hi Beach!

Glad I took some of your advice and licked that problem! :)

Sounds good on your exhaust mod. Is it worth anything to un-cap it? I'm not quite done yet,and want to get those sticky mickeys back on(manually shift it again) and get that mid 11 at hopefully 118(just guessing). Just curious...it's a haul to Atco..it'll prolly be going with the muffs off and the sway bar in the garage. I will let you know how it runs.

Nice runs :)

JD :cool:

gkull

Beach - I was hoping for the best for you. Impressive 60's :cheers: I was wondering about. Are your injectors or program able to keep up with higher flow potential.

Beach Bum

Raysur,

No, they're not mandrel bent, the exhaust was custom built and his bending machine probably took 1/8 to 1/4" maximum out of the ID at the bends. I didn't pay much for the labor or pipes, but its a friend and fellow racer who happens to own his own performance exhaust/muffler shop that did the work. Email me if you have an application you need help with.

BobaVette, The fit is good, the exhaust shop takes a lot of pride in their work... the pipe looks stock from underneath and the rear except the pipe is a bit fatter as expected.... the exhaust is stuffed up against the bottom of the rearend just like stock... so its logical the exhaust sits 3/4" lower than the stock pipe, still plenty of clearance back their... I worry more about my front spoiler and Miloden oil pan.

JD,

I'm glad you ran better... but I think you have a LOT more in your set-up... Ralph told me via email you guys had -400 to - 900 DA this weekend.... with your set-up and raceweight, you should have been up around 118-120 in that type of air. If a little timing was good... then a lot must be GREAT..... well not exactly, but I'll bet a nickel a little more might help... experiment.

It appears when I corked the exhaust I was only penalized roughly 1/2 tenth and mph... however, this is in-conclusive, I need to do a lot more than just 1 pass on the corked vs uncorked comparison before I can accurately state the effect.

Gkull,

Good Question !!! and I dunno.... I've been thinking the same thing considering some of my modifications don't seem to be working lately. I'm actually thinking the MAF might be starting to be a restriction, or maybe the chip... or maybe the injectors too.... but dunno, could even by my manifold.... pretty hard to get a Superram into the low 11's or high 10's on a pump gas true street car from what I can tell. :(

thanks for the replies. :)

Beach

427Hotrod

Your results are very close to what I experienced with my '67 when I had the 427 in it. It didn't gain anything from opening the headers that I could measure at the track. I tried back to back testing including jetting and timing loops and couldn't move it more than a half tenth or even .5 mph.

That was with 2.5" non-mandrel pipes and 2 chamber flowmasters. It was running 11.20's at 122-123 mph. Chassis dyno was 423 RWHP. The essentially same engine (without as good a set of heads) was in my Camaro for a number of years and it would pick up between .1-.2 tenths and 1 mph uncapped.

My new 540 is a whole 'nuther story. I ran it initially with the same 2.5 pipes. I later installed a set of 3" pipes under it assuming it MUST be choked up. During my recent chassis dyno testing I found out that even the 3" is killing it. It picked up over 45 rwhp by uncapping it!! That's a ton!!

So I believe your conclusion is dead on. 2.5 " will handle 90% of everything out there and 3" will get the next 5%. I guess the last 5% need to figure out how to squeeze 4" oval pipe under a C-2!!!

Cubic inches and/or RPM make a huge difference!!


Jim

Beach Bum

You know I really tried to do my homework before executing this modification, I asked a lot of different people with a lot of different set-ups.... and about 50/50 experienced or was their opinion I would pick-up some power.... but the real kicker that put me over the top on doing this modification was that GM put 2 1/4" stock exhaust in the 230-250 HP L98 motors from 85-91, and they put 2 3/4" pipe in the 300 HP LT-1 from 92-96.... it seemed logical that GM felt the additional HP mandated bigger exhaust pipe, thus my silly logical brain came to the conclusion that my 383 440 HP motor must need 2.75" or bigger pipe to be optimized too.... well it appears unfortunately thats not the way things work.... I don't have a clue why the LT-1 has 2.75" exhaust pipe from the factory.... but I doubt if it had to do with making more HP.

I think you can throw logic out the door when it comes to hot roddin our racecars.... :crazy:

later
Beach

427Hotrod

Yeah, the factory may have done it to fight some resonance issue or just an over all noise factor. Could have to do with the restriction of the stock cat. and mufflers. With smaller pipes and the additional restriction of the stock components it might have been just a hair too much without some larger pipes to help out.

I'm with you though, the General wouldn't have done it if he could have found a cheaper way to get by.

You know what they real problem is though don't you? It's not that you have too much exhaust.... you just need more motor!!!

Christmas is coming!! If you've been real good and beg Santa....


Jim

ol,RJ

nice job on the testing Beach Bum,
did you try some more (adjusting) fuel pressure?
larger exhaust can more the HP and TQ peaks up some in the rpm range, you may even need a slight change in your shift points to take full advantage of it.
you have sounded a little disappointed about the mod's lately, just remember that it takes a LOT more power to make gains in the 11's than it does in the 12's ect.
so you really are adding HP when you gain those hundreths :yesnod:
RJ

GlennS87

How much did you drive it after putting on the system? Is it possible that ECM hadn't re-learned the new conditions? Just a thought.

Beach Bum

427Hotrod,

More Motor... I like the sound of that, unfortunately the real Santa (my wallet) can't do it this year... maybe next.

RJ,

I added a little fp at the track between my 1st and 2nd run.... I slowed down a hair... I think the shift points are okay, I ran it out to 5900 rpm on all of my passes.

Glen,

Drove it 20 miles from the shop to the track before racing... that was capped up... so un-capped about 300 yards from the pits to the lights... I'm not done testing... I'll be back out to the track within the next few weeks trying to find that tenth the motor owes me....

later
Beach

BeaterShark

Beach,

Thanks for posting your results (and doing the testing). I was seriously debating the 2.5" vs 3" exhaust for my 383 (estimated 450 FW HP) and ended up going with the 2.5". When I finally dyno this thing, I'm going to dyno both with and without the mufflers to see what the difference is, but this probably won't be until the beginning of next year. I'm running some 2.5" glasspacks with perferated (read: straight through) core.

Fastguy

Well, I'll be running Hooker Super Comps with true 2 1/2 duals and Walker mufflers on my 383. I'm glad to hear that I won't be losing much power by staying with a medium sized exhaust. I might throw it on before I get the new motor in just to see what sort of difference it will make on a stock L98.

scorp508

I dunno, our computers are pretty dumb. No real learning curve or way to store any updates.