I have been running a 2 1/4 reducer on my headers with about 12-16 inches of 2 inch pipe, followed by a 17in long, 2 in diameter glasspacks. The glasspacks are not fiberglass packed.

I think it runs good with the 2 inch pipe, and sluggish with open headers. Anyways am I choking my exhaust with the 2 inch pipe, and should i try 2 and 1/4 min?

what do you guys think? BTW i have ball and socket hedmans.

 

looks like from i am running 32-34 inches worth of exhaust, waiting to get some money for a full exhaust.

 

I'd go the same size as the collectors, then I'd throw out the glasspacks and get some real mufflers.

I had a glasspack on my old Exploder. It was cheap, and the old muffler, and surrounding pipe, rotted out. Cheap-o glasspack, turndown, fixed! Well, the fumes eventually worked their way into the cab, so I did it right. Cheap cherry-bomb muffler, real tailpipe, weld all the connections.

Something happened I didn't expect: Not only was it 1000% quieter, it had more power too!

 

i kinda like my glass packs, they don't sound like turd turbo mufflers. But what i like better is no glasspack, the louder the better. That only used to be $28.50.

So Kurt are you saying 2 and 1/4 reducer and pipe?

 

I think you're OK with that exhuast. The 901 cam isn't enough to stress any of your other components. I ony run dual 2.5" exhaust at the recommendation of Stan at FPA (header guru). And, I've got a good bit more cam. I'd work on other stuff before messing with your exhaust.

 

I also like the little 901 in my boat. I think its about time for me to make a gallery and show you guys what a 901 can do. I am not doing anything else to the motor, just want to finish up the exhaust.

Imo i think the rpm intake is holding back my heads. Along with the cam, and carb.

 

I'll disagree about the RPM intake. Even with my poorly tuned dyno, the HP peak was right where Desktop Dyno said it should be (indicating that the components were working as planned). But, I am running Edel heads as well, they probbaly match well with the Edel rpm intake.

I'm not criticising the 901 cam. I think the FE responds well to small improvements, including the cam. It's also a lot easier to get a smaller cam to run well. Another advantage to the 901 cam (so long as it's in the appropriate comp ratio).

I like beer.

 

you like beer too? I know you will be drinking tomoorow night after running a 13 second slip, hell you probaly get paid tomoorrow as well.

Greg, I don't know about you but i am a bit of a bench racer. From what i found the RPM intake flows 229cfm on the upper plane and 215cfm in the lower plane. Don't get me wrong, the rpm is a great intake but I got a big itch for a MR blue thunder. And i think you would benefit as well. 229cfm is a choke on an advertsied 270 port. I am not sure what the specific flow is at your lift.

LIke i said Greg, you would benefit greatly from a MR BT.

 

Well, what I am saying is, whatever the diameter of the header collector is, run that diameter pipe! Go smaller, you restrict it, go bigger, it creates an expansion chamber, turbulence, and that restricts it. Go to the same size pipe as the collector is, and everything flows happy! Make any sense?

 

gtex's got the right idea.... i run 2.5" into dynomax and then 3" straight out the back.... nice and quiet in the cab when cruising- loud as all get out with the stupid pedal to the floor!!!

 

The glasspack is a restriction to flow. A good turbo type muffler(Hooker Aero chamber, Walker Super Turbo, etc.) will far outflow any glasspack. BTW, I thought a glasspack was, well, packed with fiberglass????? They quiet noise by directing some exhaust into the packing.

 

The first question is, what RPM do you run your truck at? The lower the rpm range you run, generaly, the smaller the pipe you need. Too big of a pipe and it will act like it did with the open headers; it Bogs down. I'm running 1 7/8's dual pipes, but my truck rarely gets over 4500 rpm, and spends most of its time between 1k and 3k.

A glasspack without the glass is actualy an Expansion chamber, also called a resonance chamber, or a reflective Muffler. They work fine with low restriction. All mufflers work by trying to remove the soundwave from the exhaust gasses, either by canceling it with reflection or absorbing it is a dense material, or distorting it by compression. A turbo muffler is designed to be on a system behind a turbo. because the turbo is compressing the exhaust to spin it's turbine, the gasses come out with most of their soundwave stripped.effectivly, the turbo its self is a muffler. The turbo muffler is then designed to deal with the specific shapes of soundwaves left behind. It does Not flow better than a comparibly built glasspack or expansion chamber,unless you have a turbo on the engine. It doesn't muffle the noise as well as a muffler ment for a normaly aspirated engine either.

Most of this is unimportant. Choosing the wrong muffler, as long as it's the right size and relitivly prefomance basd is not going to cost you more than a couple of horse power. Muffler choice is more about the sound; Making the truck sound good while keeping the cops from ticketing you every trip around the block. Pick the one that sounds the best to you. personaly I like the sound of those resonance chambers that look like cherry bombs when they are set up near the headders. Deep throaty growl, but quiet.

The real gains from your exhaust come from the pipe. As you found out, open headers will make the engine bog down. The reason for this is that when the exhaust gasses leave the combustion chamber, they leave in a pressure wave. The wave has 2 parts, the highpressure head, and the low pressure tail. Its this tail thats important. think of it like a mini vaccume. the Ideal sized exhaust will line this low pressure tail directly infront of the highpressure head of the next cylinder's pulse. Aside from helping to scavange and empty the cylinders, this also helps to pull the exhaust down the tailpipe. what you end up with is a pipe full of pressure points, high, low, high, low, and all averaging out to zero. with this over all average of zero, and the inertia of the gass already moving, engine doesn't have to work very hard to clear the exhaust.

If the exhause pipe is too large, then these pressure waves slow down. the high pressure head of one pulse may sit ontop of the low pressure wave of another pulse, ruining its scavanging effect, and ruining it's ability to pull the next wave along. what you end up with is slow moving exhaust with no low pressure points, so the average pressure in the pipe is high, and the engine has to work harder to move it out.

Too small is also a problem. the exhaust gas pulses may line up like they should in a correct size pipe, but with the restricted size, the low pressure pulse won't be low enough to be effective, and the engine will have to then work to overcome the high pressure in the pipe.

 

66beater's got the goods in his first sentence.. what RPM? I spin my 390 6200 on the street and twist it up to 6800 when i'm racing.... i gained some top end when i went to that 3" from the mufflers back.. low end isn't an issue with 4.10 gears and a 4 speed and 10.5:1 compression.... depends on ur usage though.

 

66beater...the turbo muffler was originally designed for the Chevy Corvair turbo car, the term has become somewhat "generic" in that it simply refers to the shape of the muffler. It needed to flow BETTER than the typical mufflers available at the time, because the turbo causes a higher flow of exhaust once spooled up. I have not seen a flow test yet that showed the glasspack flowed better than a good performance turbo STYLE muffler. The Hooker Aero Chamber flows as much CFM as an equivalent size straight pipe.

 

Wow..... I'm not sure I understand all that but suddenly I feel like the 2 1/2" hemi turbos I'm going to have installed next week are too big.... the motor might see 5000rpm....I'm running reducers right off the headers but I feel like I should have some 3" pipe coming a little ways off the headers to extend the collectors...maybe I can have the shop do that...

I have the same headers and about the same exhaust except 2 1/2" into summit turbos.....but way to loud for me.....I'm not going to run tailpipes so I'm hoping that the hemi turbos (dynomax) and a balance tube will get me the sound I'm looking for...good luck with whatever you decide.....I would think 2 1/4" min ....but I'm hardly an expert