Batazz LOL. Well it is, if your single mufflers flow is not enough. With duals coming out you can use two mufflers and each bank shares the flow. Two 900cfm mufflers can support more hp than one. That makes up the zero hp loss and great sound control. Best of both worlds.

 

hmm...i'm currently running a single 3.5" dynomax bullit. sorry badazz....got that spelling all messed up there...

 

Uncork the headers on your car and those short little collectors will have your engine falling on it's face. Don't need to prove it, just try it. All that bottom end torque you had with the exhaust bolted up goes out the window because the tuning has gone for a sh*t. Just like the sub woofer you tune with a cabinet, headers without SOME sort of extention on the collector won't work very well unless of course you've built an engine that wants really short secondaries, like a top fuel engine that has NO collectors.
The point of the "magic box" is to provide the engine with what it believes is an open exhaust with the proper spec secondary. That secondary length is extremely important.
You like a sleeper? Show up with open header performance (and not just uncorked headers) with a relatively quiet exhaust and get plenty of suckers.
Incidentaly, if you run true duals and have a couple of glass packs, it's possible that you've hit upon a resonance that giving you exactly what you need it terms of exhaust.

Science is freakin' wonderful!

 

cooool

 

Removing your stock manifolds and single exhaust and installing headers with dual exhaust will give you more horsepower won't it?
No way!
If you think or know it does, then apply that same thinking to the next step in improving your exhaust. Open headers are a heat score.

 

That's ok, what kind of power are you making. With a 3.5" bullit you should be ok, loud but ok.

 

Just for giggles, when I run my car on DynoSim the difference between open collectors(termination box) and mufflers is over 30hp.

 

That's about right with tunning. A non-thought out exhaust system will cost you a lot of hp/trq just like the wrong cam or intake. But some people don't mind that i guess.

 

well...that's a good question. my 305 has been 12.38 @ 108mph in the quarter at 3230lbs. raceweight...which by use of my magical online horsepower calculators equals ~ 327rwhp, but i think that might be high because my car is incredibly efficient. i'm not looking for optimal hp numbers necessarily, but rather the best combo for all out drag racing.

it is loud. right now it's unbareable as a street car because it dumps right in front of the rearend. i'm planning to take it all the way out the back and dump out by the bumper ala mufflex system. i want it quieter in the car, but i still want a loud sick nasty sound outside of the car. i'm no longer looking for a sleeper necessarily. new combo will be a manual transmission and i'm looking for ~450+rwhp...n/a.

 

I hear ya on the loudness Matt, I havent ridin in the new exhaust setup but I couldn't imagine how load it is

 

That sounds like a mean combo. 12.38 with a 305 that's real good. If it wasn't so loud you would make a lot of money around here. (Mudstain guys don't give the 305 any respect)

 

And I find that worth pursuing.
Just not now......

 

Hey Orr,
I checked out your start up vid.
How about some pics of the finished exhaust?

 

well thats the thing, its not 100% finished yet. I dont like how low it sits and not sure i like how loud it is

I'll try to post up a pic of what i got so far and what changes i plan to make

 

Cool.

 

Updating:

Final pics of my setup for now It will change if i swap to a T56 or something over winter or fall, depending. Still low but gives me enough clearance to do what i have to do with this car, even tho clearance is about 2 inches...its scraping pulling into the garage haha but on the roads and with the new tires i have it should be closer to 2.5 inches total clearance









Kinda feel bad that after this LONG thread about good exhaust building ideas, i didnt fully go thru with the main idea of this thread. BUT this is the starting point for this motor. It can all change later if i dont like how it works. But I have tried the Split Flow by Dynatech and it was louder than i liked. I know sport the Dynomax ultraflo round 6inch case and i like it. it was loud too at first but did quiet down some with the tail pipes finally added.

I'm happy with what i have so far, its just a starting point for this motor. Its not the prettiest job nor the cleanest welds/install, but it is more than enough for me at this time

 

Hi Orr

Good to see you are making progress and thanks for posting your update. Remember it took me about nine months to get mine all sorted out trying to figure out what the heck was going on with the motor. These thing can take some time.

 

yep i think i have a trans problem and now a bad lifter noise it sounds like...so i hope one of the lifters didnt go bad already.

gonna change oil tomorrow and see what happens

 

wow thats pretty low, you cant put a jack under there and try and bend that pipe up some more??

 

already tried that and it didnt really move... it is very low but for some reason on teh street it kinda works good

 

Good work.
I hope you still intend to pursue the tuned exhaust idea.
You have a chance to develop what you've got and expand from there.
Wish I could have stopped in on my way back from Virginia, but the scheduling was really tight.

 

i think that would be beneficial... i'd love to do some open header tuning/testing with proper length collectors just to see how it goes over my current system.. Maybe i'll do that on the dyno someday but we'll see

 

I have long tube Hooker Super Comps on my 383 and ran dual 3" back to two chamber Flowmasters dumping at the rear axle. The shop flattened the pipe a tad that runs under and around my crossmember for clearance and we beat up the floor where the mufflers hang, gave them good clearance after that. The lowest thing on my car is the crossmember for my Southside Machine bars.

I had to put tail pipes running out to the rear of the car when I was hauling my kids around and it killed the motor.

 

Hey Orr did you see the post on the Corvette forum where the guy made 475rwhp with a similiar combination to what you are doing? It was a very impressive performance. Nothing wild about the combination and the heads are very similiar to the ones you are using.

 

his heads flowed like 286 and are comp ported 210's to my standard 195's. BUT the bench they used showed stock LT4 heads to flow 234cfm when most show near 250 so i bet those 210's flow closer to 300-305cfm easily

My cam is similar, slightly less lift but more exhaust duration and more cubes to my motor. i dont expect 475whp but atleast near 420 would be nice Thing that worries me is that he made that power on open headers i believe to my full exhaust theres that tuning thing

And my car doesnt idle that nasty like some cammed cars and so far it drives too tame to be a 400+whp car haha. even on base tune its driveable as can be and that worries me that its not making near the power i expect...we'll see tho

 

im running a similiar setup on a 355, im thinking about going carb cos the fuel injection just doesnt have the power but im not going to give up on it yet gonna try some more until i want to throw it at the wall then ill go carb. With my combo im supposed to have like 400hp, doesn't feel like it.

 

"And my car doesnt idle that nasty like some cammed cars and so far it drives too tame to be a 400+whp car haha."

I hear you. Mine is the same way as it is very tame at low rpms. However when the pedal is to the metal it becomes another car.

Regarding the exhaust. That is why I'm building my own drive shaft loop and at the same time relocating the transmission cross member to the rear around 6". That will make plenty of room to pass and exhaust pipe through the area when I build the termination boxes. From the simulation I have done we are talking a good 30 hp from a muffler system to an open exhaust system.

I have also decided to redo my cold air intake one more time. I want it to flow a true 1300cfm to match my throttle body. In order to do it I have to use two air filters. They are round at 7.25"D x 5.50"H each. I also want to have a nice 3/8" radius inlet into the air pipe from the air filter chamber.

I think with some tinkering and fine tuning your car is going to surprise you.

 

i hope so. gonna fire it up and take it for a little drive today. Do some tuning maybe

I think the stock airbox setup is gonna kill this motor so i have to do that next.. gotta make a CAI of some type with a bigger flow path. stock MAF tho will be the new restriction

 

what torque converter are you running with orr89rocz?

 

Edge racing 9.5" 3600 stall roughly

 

I am thinking of getting my re stalled to around 3500. Right now I am at 2900 and think its hurting me at the track. How well does the 3600 work on the streets? Any suggestions on what stall I should run from your experience?

 

i have no problems with 3600 on the street. The 383's torque and the converters specs allow me to use this very easily on the street. It is a 3500-3600 stall but it acts alittle tighter than that at low loads/rpms so far.

I'd say you'd need atleast 3400. 3400-3600 is a great streetable torque converter for a 383

I had 2800 on my Bolt On L98 and this converter now acts abit better street driving than my old one. Its all in how they set it up i guess and how much low rpm power the motor makes

 

on the dyno my motor makes the most torque at 4000 rpm

 

Good rule of thumb i was told was to keep converter speed 500 rpms below peak torque. I expect my torque to peak in the 4400 range and went with a 3600 for streetability and possibly a later nitrous shot which will make it stall more like 4000

 

how much of a timeslip difference did it make going from a 2800 to a 3600?

 

never tested it. 2800 was in my old L98. I took it out restalled it to 3600 for this 383 which i just put in, and is still breaking in but getting closer to dyno time. Soon as its inspected i can start driving it and put some real miles on it. Then I can drag it and dyno it

But i did feel my combo would have liked more gear or abit more stall speed. Granted i made peak torque from 3000-3500 so 2800 wasnt to far off that combo, but i think 3200 would have been perfect. Probly would have netted me near .05 on the 60 foots dropping me from 1.70-1.71 down into the mid 1.6's.. that is worth a tenth on the big end atleast.

 

I went from a Corvette convertor which may have provided around 2000 rpm of stall to a TCI Breakaway which has a advertised 1500 over stock.
Instant improvement from a previous best of 14.xx sec to a 13.75. Street tires were no longer an option at that point. 2/10ths in 60'.
An uipgrade to 1.6 Pro Magnum rockers squezzed out another 2/10ths.
Now I've upgraded to a TCI Street fighter which should stall with my NEW combo at around 3500 rpm. With the new convertor, a fresh from the machine shop short block ( thanks to a wasted flat lifter cam) and XR276HR cam, I expect 12's.

 

just wanted to put up my final picture of what i have done as a baseline to this motor build and future plans if i think i can get more out of it. main pics are a few posts up on this page, as i posted up awhile go when i first finished the system.

in summary, its a 3inch y pipe into 4inch outlet, into dynomax ultraflo round over the axle splitting off into another 4" to dual 3" y pipe splitter and finally dual 3inch outlets going into 3.5 inch tips.

I got one better daylight pic of the rear exits... alittle offcenter but not big deal to me, i can bend the pipes over abit to better match




System sounds good, and seems to flow good. car went 11.67 at 116 so far and its not 100% tuned and it was HOT out

i still have a few leaks here and there along some of the joint welds so i will patch those up as i find them. I dont know how much if at all that effects my system but keeping pressure up inside to keep flow velocity up helps i'm sure

Future plans to this system will include the possibility of cutouts at the proper or near proper PIPEMAX calculated collector length. ELSE i may just take the exhaust off completely and run just open straight extensions at proper length. Cutouts will be easier to do tho

I will make that decision after i get done fully testing this car with the current setup. If i'm happy with the power and cant be sure i will gain more from it, maybe i wont go thru with it. But adding cutouts wont be that hard and certainly cant hurt to try them.

 

I think a lot of us are interested in following the progress on your car. I think those are great times for the first time out.

Myself I'm just going to go with the exhaust terminator boxes form the getgo while doing the enging change. Easier and cheaper to do it all at once.

 

yeah i hear yah. If all goes well i may do tubular k member and T56 over winter/spring next year. That way i could really tuck my exhaust up. I may go duals that way or keep what i have and really try to do the boxes. we'll see when that time comes. I just reallllly want to know what 18-19inch collectors do for this car compared to full exhaust. if its truely worth 20+hp, then this car will be very nasty I think theres 20hp left in a tune and CAI.

 

There's another 50 hp available with a tuned open collector and the proper fuel curve. No question.
I checked some cfm muffler ratings. The DynoMax Ultra Flo welded muffler delivered 1,133 CFM (if this is yours) which is just enough to provide zero loss from back pressure at 500 engine hp.
You, my friend, appear to be making that much and more.
Mind you, once to get to roll cage territory, do you relax and say fast enough...?

 

Regarding the "tuned" collectors here is my thought on the subject. I have my intake runners "tuned" to be in the 5800 to 5900 rpm range. I'm going for the "tuned" exhaust collectors to be in the 6400rpm range.

The way I see it the intake runners will be coming out of tune about the time the exhaust will be coming into tune. That should spread the "tuned" rpm range quite a bit to get the maximum effect.

On DynoSim it shows a good 30+ horsepower gain with the open collectors on my combination. Orr's will probably be more than that.

 

jeez you really think its that much? haha ok i'll definately pursue this

never. stage 2 will be AFR 210's single plane converted EFI, and solid roller 10's on motor, maybe 9's on the bottle?

OR new heads with larger cc chambers so i can add some boost via single turbo nothing major just 600whp

 

Wouldn't a fella be more inclined to tune the exhaust for some torque production down low?
We have pretty heavy vehicles for drag racing and anything to help the 60', I think, would be the way to go. Or is it that you TPI guys already have low rpm grunt and don't need to boost it.

 

[QUOTE=Orr89RocZ;3831463]


never. stage 2 will be AFR 210's ...


Can I buy you're 'old' 195's?

 

that looks like it turned out well, does it make alot of noise from hitting that cross member?

 

"We have pretty heavy vehicles for drag racing and anything to help the 60', I think, would be the way to go. Or is it that you TPI guys already have low rpm grunt and don't need to boost it."

You may have a point and only time and testing will tell. I'm increasing my cubic inch from 355 to 369 and doing nothing that will decrease my low end torque. In fact everything I will be doing should increase the torque throughout the rpm range. So for now I do not see a need to increase the torque down low. I'm having problems hooking up as it is.

 

lol if i do decide to go that route, i'll give you first dibs But we'll see how much i enjoy this combo this year. still alot to get out of it haha

i honestly cant tell haha. car is abit noisy itself so i dont hear as much as i would like. but it doesnt make much noise that i can tell. I have header wrap on the crossmember where it rests on it, and its pretty rigid as is, so it has a tad of vibration but its not loud. I think it turned out much better than expected.


As far as torque goes, more is always great to have, but makes hooking up harder. So as long as the car is ready for it, go for more torque when you can. Else leave it alone. you have way more than enough power/torque in the midrange with a healthy 355 let alone a 370+ inch motor. The converter speed will take advantage of what torque you do make. Let it eat

 

Just saw this posted by Larry Meaux of PipeMax fame on another site. So according to Larry the collector size and length is all important and gives the most torque and hosepower.


Short answer "Trends" =>
1- Equal Length Primaries=>
gain Peak TQ , sometimes narrow TQ Curve

2-UnEqual Length Primaries=>
broaden TQ Curve at expense of absolute Peak TQ output

3-Much more TQ + HP gains to be had with Collectors
than Primaries's Lengths
_________________
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRace

 

dyno appointment next thursday...should be good to go unless something comes up