you know what, you never identified what hp & tq numbers would be in the range of what you expected. I agree 228 and 338 is low for the cubes you are running.

exhaust, carb and intake increases will net you some but not the big bang you are looking for.

you are going to have to deal with cam and heads to get good numbers out of your 383. whatever you decide to do about cam you need to get at least 230+ duration and .500+ lift. anything less is wasting your cubes. 170cfm intake ports also won't cut it. Need 190+ heads or you are wasting your cubes.

oh yeah, my '90 5.7 made 298rwhp and 388lbs rwtq on a mustang dyno with stock cam and heads.

FWIW I think you need to look at a carb tune and then set timing to that tune.

 

his setup is all on the small side anyway, low compression, small cam, small carb, small exhaust that's the perfect setup for a 305 block.
A 383 is a big engine it needs alot of fuel, that fuel needs allot of air, a 600 cfm carb is barely enough for a stock 350 with a small cam and intake.

 

1 5/8" primary headers on a 383 ?
It sounds like your exhaust system is 90% of the problem.
Are you also running a CAT on this exhaust system?

You should consider 1.75" primary headers an absolute minimum for a 383.
2.5" header collectors show some restriction on even mild 383 engines, so trying to run both banks into a single 2.5" is quite excessive.
You should consider a CAT-less mandrel 3.0" pipe as the absolute minimum on a 383.
Crossflow mufflers are known to be very restrictive as well. Look into a 3" single outlet type like a Borla.

Are you running a vacuum advance on your distributor? Is it hooked up to a full manifold vacuum source? or a ported vacuum source?
Are you disconnecting the vacuum when you are checking the spark advance?

 

If you have a welder, you could buy some 3" straight and u-bend sections of pipe, and cut off the 2.5" section right where the intermediate pipes join together and weld in a 3" section using the bend and straight sections spliced together. I cant see what your working with, but thats what I would consider doing if its feasible. Other option is to take it to a reputable shop and have them modify the y-pipe. Last option is to buy a larger y-pipe.

 

Well everybody has mixed opinions about what my hp numbers should be, however, I was expecting at least 260 - 280 rwhp...

I have the carb tuned pretty decently i feel. I posted the tune in an earlier post.

 

Hmm so what do you think is worse? The primary size or the 2.5 rest of the exhaust? I believe my vaccuum advance is hooked up to manifold vaccuum, so at part throttle its uplling advance, but at WOT its 34. I always disconnected vaccuum advance and capped the port when checking timing.

 

if i was you i would leave the headers alone, do a dual 2.5 to a single 3.5 single straight through muffler, put the 750 carb back on and go back to the dyno, i don't see why your combo shouldn't peak at 5k after that, i would consider 1.6 or 1.65 ratio rockers they would help getting you more air/fuel in that engine

 

Yea that sounds like a pretty solid plan, I need to clean that 750. But the thing that sucks about that carb is it doesnt have a secondary metering block so I cant adjust secondary A/F. But I think i can buy a kit tho.

Yea bigger rockers would really help I think. I wish I could jump on getting a buncha new parts but being in college I have very little cash flow.

 

what everyone is saying is true i have a 383 with what i think are the stock heads and tpi system on it its putting down 215hp at 4200 and and 420tq at 3800 to 4000 with long tubes and looks like 2.5 exhaust and a flowmaster uncorked headers and picked a couple hp up but lost tq
but dont really know about my engine was in the car when i bought it just seemed to run pretty decent so i dynoed it

 

From the description of your headers they have 3" collectors. Everything from the headers back is worse.

My point was that a pair of 2.5" collectors is restrictive on a 383. What do you think happens when you run both banks into a 2.5" pipe?

Tuning or rocker arm changes will be futile until you address the main restriction in the system.
Once the restriction is removed you will need to re-tune.

 

Yea they are 3" collectors. I never knew what size was big enough, but I now know I need to definately step it up.

 

Ok, Im getting ready to order exhaust parts. My plan is to use my y-pipe and swap its collector to a 3.5" then run a single 3.5". I've been reading and researching a bunch on mufflers an cannot decide which direction to go... I know I don't want chambered.

How annoying would a dynomax race bullet be? I'm guessing reaal loud.

A turbo style i've heard good things about, but they are pretty pricey on summit.

Does anyone have any suggestions for a muffler that would produce good power and not be crazy loud at idle and part throttle?

 

Magnaflow's are audible but not obnoxious, don't know if they make a 3.5" though.

 

They make one.

 

Never personally had a combo that required larger than a 3" so I never looked into it.

 

3in is good enough. Don't get onto the hype of bigger is better.

 

"Magnaflow's are audible but not obnoxious, don't know if they make a 3.5" though"

They do and that is what I am running on my car.

 

Well from what I've seen 3.5" would be ideal, not too big but not too small. A single 3.5" is still smaller than a dual 2.5" and most people don't go smaller than that I thought. This is a dynomax chart.


After listening to a bunch of clips of the dynomax bullet, it doesnt seem as loud as I expected. Its hard to really know though. So right now I am leaning towards that, but the hooker aero chamber is also interesting me. How restrictive is that?

 

Ordered 3.5" piping and a dynomax race bullet. After listening to Blugrassz exhaust I was sold. Sounds reaal nice @ 27 seconds.
http://www.myspace.com/video/vid/29558936
I just hope its not so loud that I can't have a conversation in the car.

I'm gonna hopefully start mocking the exhaust up on thursday. I'm hoping to weld it myself, it will be my first time but I think I can do it.

 

"I just hope its not so loud that I can't have a conversation in the car"

I am running a 3.5" Magnaflow and it is pretty quiet. No problem at all having a converstion in the car. However if you put the pedal to the metal then it gets loud. But just cruising around it is pretty mellow.

 

Your combo reminds me of my old combo. My old engine would peak early and wouldnt rev pass 5500 rpm made like 220ish rwhp. I swapped the hei for a full MSD setup which cured my problem.

 

Every single thing in that engine is just way too restrictive. If I were you I'd just start over with the shortblock and build a whole new engine around it.

 

Well got my exhaust parts in, wow I would sure expect that this will flow sufficiently.





Hopefully the system should be all together by Saturday. Any tips for a first time exhaust build?

 

Well I put the car up on the lift this afternoon and found that the collector bolted to the headers were very poorly fabricated. There is a 2.5" bend welded to a 3" stepdown. What they did was insert the bend through the collector atleast an inch and a half and just weld it there. So inside the 3" collector you can see the 2.5" pipe sticking way through and not just butt-welded. So I am pretty much ditching the whole Y-pipe and building another.

 

Here is some pictures of my old exhaust.



And the new setup... Overall I think it came out pretty good.




I wasn't going for a "sidepipe" look, but running it this way gave me the most ground clearance. If you are less that 10ft away from the car you just see the exit. I don't have a lot of ground clearance but enough to fit over speedbumps. I know I gained power. Hard to say how much but I do feel a difference in both low end and high end power. I really like the tone of it but man is it loud, set off two car alarms today just driving at like 1800rpm.

Now I need to re-tune my carb.

 

If you're using shorties there's really no good reason not to have ground clearance like you would if it were stock. Did you just not have enough pipe?

Either way that will suffice until you get tired of the volume. If you can make it over speedbumps dont worry too much about it. And the way that's setup if/when it gets crushed and damaged from scraping it wont be a big deal to cut it and fix it. It's not like it's going to rip your headers off or something which was my big concern back when my LT's went to 3 inch duals. Anyway when you get sick of it just get a friend to run the pipe over the axle. Hell you could buy a stock catback and just modify it to make it work from there. I've got a 3.5 inch pipe running the stock route and I've got LT's. It's not as good a clearance as stock but it's pretty close.

 

Well I did everything I could to maximize ground clearance. The only thing that I can think of is using bends with a tighter radius. The main reason I ran it like it is, is because it was my first exhaust build and I wanted to keep it as simple as possible.

So yours goes next/under the driveshaft? I looked at going that route but it still looked like I would have just as bad clearance.

 

Running it over the axle is a bit of a pain in the *** to fab up on your own. I would get a factory catback and figure out how to get em to mate up. Understand I have long tubes, but that makes it harder, not easier.





This is the original setup, but I got tired of hte bad ground clearance at the muffler, which is similar to your ground clearance there:



Remember, this is a 3.5 inch pipe. We just took off the muffler and then added a clamp, and ran a new pipe over hte axle. If we'd run it like this from the beginning we probably could have tucked it even higher but it's good enough that I've never scraped it on any speed bump, and the lowest point is that clamp. If the clamp gets caught and yanked off, no big deal, nothing will get seriously damaged since the clamp is the weakest link.

I dont see why you couldnt have angled and pointed the 2 into 1 merger parallel to the rockers and then taken it back into the driveshaft tunnel. Is it too long/big and end up hitting the floor pan there or something?

Either way I dont think you did anything wrong, Im sure it'll do the job pretty well.

 

The Mufflex 4" system goes over the axle without any clearance issues so a 3.5" is definitely possible. I bet you hear the exhaust quite well with it dumping right behind the pass door.

 

Running the 3.5" Mufflex on my car with no problems. The 4" is tighter and has to be installed with care.

 

If I am interpreting what you are saying correctly, that is exactly what I did. Placed the merger behind the right front tire up in a little nook. It fit pretty perfectly and set up the 3.5 sectoin to shoot straight back. But it is parallel to the rocker and car.

One thing I did learn (first time welder) is that when fitting the pieces together really try hard to have no gaps to fill with weld. Makes it so much easier to blow holes through when there is a gap.

 

I guess I will deffinately look into the mufflex system WHEN I get tired of the noise. Because its not an if, its a when haha.

 

You have everything close to stock routing, and then instead of sending it back to the driveshaft tunnel, you dump it at the passenger door instead. I was just confused why you sent it straight back instead of sending it down the driveshaft tunnel (ie stock routing)

 

Ohhh, I looked at going that way but there was not a good spot to bring the pipe across to exit on the side. The floor pan was in the way for that. If I was to run to back over the rear end I deffinately would have gone that route.

 

Okay that answers it. The only way you'll ever get decent ground clearance is dumps at the axle near the pumpkin with bullet style mufflers (which you have), or taking it over the axle using the stock route. What you did will work fine for now though.

 

With the exhaust pipe under the passerger door, it make too much noise and you and the passenger will smell the exhaust. You would have been better off buying a decent cat-back system. You live and you learn. Get a cat-back system and use that muffler in the stock location.

 

It may be cheaper to build your own depending on how confident you are. I think I had around $200 or so in my 4" 'Catback' including the hooker 4" in/out muffler and the turndown on driverside rear bumper. That's with going over the axle with a stock panhard bar and no reallocation bar kit.

 

Well my goal was to have a nice flowing exhaust system working with little money, so in that sense I accomplished what I was trying to do. Plus its cool that I built it myself and now have that experience. Buying an aftermarket Y-pipe and cat-back would have been almost double what I spent. But eventually I will build or buy a nice full length system.

 

I'm hoping to hit the strip within the next month or so. My first time was last fall and only managed a 14.5 @98mph. I found a cool website with a ton of different performance calculators.

http://www.wallaceracing.com/Calculators.htm

Using the HP calculator from my MPH, it said 230hp which was pretty close to my dyno. According to this calculator every MPH is about 7hp gain. So I know if I gain anything over 2MPH the exhaust deffinately made a difference.

 

so how is the project coming along now?

 

Its been pretty good, managed to have no tickets, still can hear, car rips through the gears much better... especially 4th gear. Unfortunately have not been to the strip yet to really see the results. Just got a nice job so some more performance goodies will be bolting on soon.

 

in for future updates

 

Picked up a used performer rpm intake today, getting a holley 750dp mechanical secodaries soon. Gonna get those babies cleaned up and looking nice and pop them on. Also doing an oil splash shield and egr block offs to keep the intake cooler.

Was going up to New England Dragway on friday but weather was no good. Gotta make it up there at some point soon.

I'm also really interested in 1.7 roller rockers but read that the S/R torquers require modifications to the pushrod guide holes to allow this. Anyone have any experience with this?

 

Well, for whatever reason, not sure why, my cam lobes decided to take a vacation. Oil pressure dropped to 15psi at idle due to the metal dust that is coating the internals. So I am rebuilding and replacing bearings, gaskets, cam, lifters, springs, intake, carb, and possibly gasket matching/porting. Would love to hear what everyone thinks for a cam choice and anything else. I started a new thread dedicated to the rebuild located here.

https://www.thirdgen.org/forums/tech...-re-build.html

 

Hopefully pulling the engine saturday or sunday. Pretty much ready to pull out now. Heres a pic a few days ago. The exhaust is off now and tranny unbolted along with clutch linkage.


Hopefully I will be able to clean up the engine bay some and throw some black paint on it.