size & "H-pipe"

[Lonewolf3165]

disagree on 2 1/2" pipe. had 3" on a stout 406 sbc,had tail pipes put on it, out behind the rear wheel wells. wasn`t mandrell bent. ( BENDS CAME OUT ABOUT 2 1/2"). I could tell the diff. when I started it and backed it out of the muffler shop. put about a hundred miles on it, pulled them off, went w/ two 3" into 3' flowmasters, then dumped before the rear wheels. get this, those tailpipes made almost 3 tenths diff. on the dragstrip!
if anyone wants 3" dual tailpipes for an 88-98 chev-gmc pick up, (mufflers back, (will have to move gas tank to runem) I gotem layin in the barn, not even rusty yet>-------------bob

3/10, you had more problems than just tube diameter. Just saying.

 

[Mad Dart]

3 inch is what you need. And X pipes are useless. Get an H. I have 3 inch with Tail pipes. and tips with 2 1/2 H. Mine don't hang down or hit anywhere with a large solid roller. Sounds like a new Cadillac and flows like the Hudson river during a flood.

So your exhaust dumps in 2 places, at the rear axle and at the bumper?

 

[Lonewolf3165]

So your exhaust dumps in 2 places, at the rear axle and at the bumper?

I saw that too. That is certainly an interesting system on that. Is there a cut-out?

 

[Oldmanmopar]

No there is no cut out. And yes it dumps at two places. The turndowns under the car are how I wanted to get rid of the exhaust. Mufflers are for the guys that look under. Tail pipes and tips are for the police walk around so it looks , sounds and , feels like its all on the car when out back and idling. The H was put in to get rid of the babble on a hard pull.

I have had the headers open. with the two bends on going passed the trans cross member detents. The car Doesn't pull as hard and it falls off at 7500-8000.

With the exhaust on crossover/H and tail pipes that only divert sound. I shift is at 8000.

The rev limit was raise to 9000 because I was hitting the limit on the shift and would sound like a RPM miss . I have seen the recall at 9300. Not intentially but because I got into a dirt tracking hard pull with the car it in second gear and couldn't shift for fear of losing it.

The car has 456's so guys with motors like this know how quick you can lose them on the street.

Its a High revving high HP SB. A different animal then a low RPM High HP BB or stroker.
It was built for the street to have fun with. And its Heart Therapy.

Lone wolf your close. Come by and I'll take you for a ride you'll talk about the rest of your life. Or never get to talk about it at all. You'll just have to sit back so I can see out the passenger side window

 

[1Fast340]

The system with the highest velocity would be the system with the least restriction. What changes in air flow in the header collector that doesn't happen in the rest of the system?

i believe you got the first part backwards:blob:

all im saying is that after the correct collector lenght you could build the rest of the exhaust with 6" pipes if you want to there wont be any loss of power,while going down in size and creating a restriction might cost power.

 

[Lonewolf3165]

i believe you got the first part backwards:blob:

all im saying is that after the correct collector length you could build the rest of the exhaust with 6" pipes if you want to there wont be any loss of power,while going down in size and creating a restriction might cost power.

I disagree that just going bigger has no effect. I'm not saying that smaller pipe is always better. Obviously you don't want a diameter that is restrictive. All I'm saying is bigger isn't always better. There is such a thing as too big. Remember the OP asked about what works on a mild BB engine. The entire system has to be efficient, right up to when it exits.

 

[Lonewolf3165]

No there is no cut out. And yes it dumps at two places. The turndowns under the car are how I wanted to get rid of the exhaust. Mufflers are for the guys that look under. Tail pipes and tips are for the police walk around so it looks , sounds and , feels like its all on the car when out back and idling. The H was put in to get rid of the babble on a hard pull.

I have had the headers open. with the two bends on going passed the trans cross member detents. The car Doesn't pull as hard and it falls off at 7500-8000.

With the exhaust on crossover/H and tail pipes that only divert sound. I shift is at 8000.

The rev limit was raise to 9000 because I was hitting the limit on the shift and would sound like a RPM miss . I have seen the recall at 9300. Not intentially but because I got into a dirt tracking hard pull with the car it in second gear and couldn't shift for fear of losing it.

The car has 456's so guys with motors like this know how quick you can lose them on the street.

Its a High revving high HP SB. A different animal then a low RPM High HP BB or stroker.
It was built for the street to have fun with. And its Heart Therapy.

Lone wolf your close. Come by and I'll take you for a ride you'll talk about the rest of your life. Or never get to talk about it at all. You'll just have to sit back so I can see out the passenger side window

Lol! Steve, looking at the car in some of your pictures & posts I don't think you have to worry about me sitting too far forward! I think I'd be back against the seat like it or not! It certainly doesn't look like it was built for the meek of heart! Just reading that made my you-know-what pucker! If I get up that way I'll PM you & you can give me directions. Do I need to bring Depends? LOL!

 

[airwoofer]

I am not trying to argue with OMM but my TTI step into 3" collectors, Jegs or Summit (cannot remember) X pipe kit, 3" x 8" cherrybombs before flowmaster 40's into dumps at the axle picked up ET and speed over open collectors and to me sound perfect. 3" all the way.

 

[Oldmanmopar]

I am not trying to argue with OMM but my TTI step into 3" collectors, Jegs or Summit (cannot remember) X pipe kit, 3" x 8" cherrybombs before flowmaster 40's into dumps at the axle picked up ET and speed over open collectors and to me sound perfect. 3" all the way.

Some motors do need more back pressure. Some don't. I feel My car runs better with the exhaust on, Then with it just open headers. An X pipe has to be more restrictive. Your motor needs a smaller exhaust. Mine likes a big exhaust.. If I could get a 6 inch pipe under my car I might need an X pipe too.

 

[jerry6]

I ran a 440 with a torker , 850 holley and 11.75 trw pistons and it ran best with 2 1/2 inch pipes , no H pipe . Had 3 inch pipes that ended at the dif , but the low end was not as strong , not as much fun on the street , a bit better at the track once the revs were over 4000 . Maybe a tenth or 2 at the track , hard to tell so many factors go into run times .

 

[Oldmanmopar]

I ran a 440 with a torker , 850 holley and 11.75 trw pistons and it ran best with 2 1/2 inch pipes , no H pipe . Had 3 inch pipes that ended at the dif , but the low end was not as strong , not as much fun on the street , a bit better at the track once the revs were over 4000 . Maybe a tenth or 2 at the track , hard to tell so many factors go into run times .

I like that lime green on 70 darts. 70 A-bodies look the best in that color. especially Darts with the BB stripe

 

[Mattax]

OMM, your example reinforces my point to the original poster (who has now disappeared or run for cover). The biggest determinants in figuring best pipe size, length, and cross-connection are engine displacement and rpm range. The OP wrote that he had a "Mild street 440 4bbl" from which we could guess that powerband of interest 3500 to 5500. Maybe even lower if never racing.

velocity is important for primary tubes on the headers,collector sizing is also important but after the correct collector lenght has been achieved all you want is minimum restriction.

On this I have to agree with Lone Wolf. Here's why. First, in a full exhaust system, the 'collector' length becomes the distance from the primary pipes to the first interuption - be it an H, an X, a muffler, or a resonance box. Second, as the exhaust temperature drops going from the primaries to tail pipe, the exhaust gas density increases and takes up less volume. From these two points, lets look at the question of achieving the highest flow possible at all rpms. (All because we're looking street or street/race situations).

Agreed that the maximum flow is achieved with the least resistance in the exhaust system. Therefore agreed that a restrictive system increases pressure for a given volume per minute. In other words, a restrictive system hurts flow. At the same time, allowing any point inside the exahust system to reach atmospheric pressure will cause the exhaust flow to stall inside the pipes. This actually happens on some race oriented vehicles (especially motorcycles) and causes problems for low rpm readings on WBO2 in the tailpipes. In many cases its an easily accepted price for more power where it counts.

In a long exhaust system, the diameter can be reduced slightly getting closer to the exit for purposes of maintaining mass flow and velocity. If the exhaust gas temperature dropped about 300 F, about a 1/4" diameter smaller could be used at the tail pipe to maintian velocity. Think of the tailpipe as a nozzle and the objective is to keep the mass flow of the exhaust moving beyond the tip.

I don't know if 300 F is a fair estimate, although I do intend to take some measurements if given a chance. My Innovate datalogger accepts K type thermocouple, but its one more thing on my to do list.... I think the temperature drop will be rpm dependent, with more cooling at lower flow.

 

[ir3333]

didn't 340 exhaust start at 2 1/4" and finish through a 2" tailpipe from the muffler back?