What size exhaust should I run

[baclay9]

I am going to be running a well built 454 in my truck. I will be running Sanderson headers. They are 1 7/8" primary tubes. I also want to run 40 series flowmasters and am going to dump them just before the rear axle.

What size exhaust system should I be running behind this beast? Should it be 2.5" or 3"? X pipe or H pipe?

Thanks formthe help!!!
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[bigsnookmaster]

I'd go 3" with an X.

[ProStreet68SB]

2.5" at the most. And dump the flowmasters, they are one of the worse flowing mufflers on the market.

[baclay9]

What muffler would you reccomend? I really like the way flows sound.

[Alex Hayley]

I like my 3" with an x dumping behind the rear wheels. I went with Borla XR-1 Sportsman 3" in/out which I really like.

http://www.borla.com/products/produc...?cat=2&type=72

When looking at mufflers, I noticed that Flowmasters are baffled and have a number of 90 degree turns within them. The Magnaflows are not baffled BUT reduce to 2.5" even if the inlet and outlet size is 3". The Borla is 3" all the way through. All of the previous information is what I noticed as I looked at mufflers and could be incorrect based on the exact muffler I looked at.

[Super73]

The hooker Aerochamber sounds very good IMO and crushes the blow master.

I recently switched from a 3" x pipe that had warlock muffles which had electric cut outs hung on them, to, dual electrich cut outs right off the collector knecking down to 2.5" and in to dual 2.5" turbo mufflers. To tell you the truth, for driving around, I could not be happier. Picks up 20rwhp on the dyno when the headers are open. So I get the best of both worlds, quiet or mean..

[bradh]

Someone posted this in another thread and I bookmarked it. Really good article. I'll be reading it again before I do another exhaust.

http://www.pontiacstreetperformance....p/exhaust.html

[baclay9]

Anybody heard anything about spintechs. I have been reading good things today and some of the clips on youtube are mean sounding. This is a link to the muffler.

http://www.spintechmufflers.com/muff...gr0qc4vdrdvtp4

Here is a link to a 454 with these mufflers behind it.

YouTube - 1971 454 Monte Carlo with...

Sounds pretty darn mean to me.

[baclay9]

After looking around I may go with the Spintech Pro Street mufflers. I am thinking 2.5" exhaust with an H pipe.

[nomrlz]

i wanted spintechs when i did my wagon but they were gonna take too long to get. i ended up with magnaflows and am happy with them. still like the spintechs prostreets tho.

[ProStreet68SB]

Originally Posted by baclay9

After looking around I may go with the Spintech Pro Street mufflers. I am thinking 2.5" exhaust with an H pipe.

that would be a great idea! very good choice of everything there.

[RatPwrd72]

x4 on the 2.5" pipe, it'll make more torque than the 3" and keep the sound to a minimum. It takes alot of motor to justify 3" pipe.

[tonypaul]

This came up in my search-
http://67-72chevytrucks.com/vboard/s...d.php?t=263014

I recently went through this same process on my BMW 850I (V12) when I wanted to replace the exhaust system. I tried 4 different mufflers, I ended up with the Borla's. For some strange reason I liked the sound of the flowmasters on the BMW at idle but the Borlas had better power through the powerband of the engine.

But as of now I have a 3" x pipe with Flowmasters waiting to go on the truck Im building now..... But its only because what I had laying around. Im sure I will be changing out the mufflers in the very near future....

[shortbed70]

I have spintek's on my 65 but cant really get a good video in the garage of it running. They are the prostreet type and man they sound racey!!! BBC go 3"

[baclay9]

Originally Posted by shortbed70

I have spintek's on my 65 but cant really get a good video in the garage of it running. They are the prostreet type and man they sound racey!!! BBC go 3"

Can yu keep them somewhat quiet if you are trying? Like say taking off from a stoplight with a cop sitting beside you? Are they just really loud when you punch it? How is the in cab noise? Can you listen to the radio ect...
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[Super73]

Originally Posted by RatPwrd72

x4 on the 2.5" pipe, it'll make more torque than the 3" and keep the sound to a minimum. It takes alot of motor to justify 3" pipe.

Why do you say this, because I have to disagree about the making more TQ.. I can show you countless dynos featuring different vehicles and exhaust designs where an open headered dual cut out design makes more power. Many of the ones I can show you show the same HP/TQ from aprox 2,500ish rpm to aprox 4,000rpm, then from there it's all win for the open system. I have never seen 1 case personally where this has shown to loose low end. I think it all comes down to proper design and scavaging.

I have tested this personally with:

My Old Camaro SS:
Long tube headers
Dual 3" electric cut outs off the headers
Knecking down to dual 2.5"
Flow Master Y collector dual 2.5" to single 3"
Single 3" in hooker Aero chamber with dual 2.5" out



Buddies 2002 Camaro SS with something similar to mine mentioned above



My truck with a couple different set ups:

347ci motor
3" X-pipe off the headers
Dual 3" warlock mufflers corked and uncorked

418ci motor
Dual electric cut outs right off the headers
Knecks down to 2.5" in to turbo mufflers


Several other cars I have dynotuned for others with various cut out set ups.

[baclay9]

Looks like a pretty even split between 2.5" and 3" pipe. Is this like a edelbrock vs. Holley argument?

[nomrlz]

i can tell you. if you drive the car a lot. the loud/racey mufflers will get annoying after awhile. the drone will just drive you nutz

[baclay9]

This truck is just being built as a toy, weekend cruiser type vehicle. Not my daily driver by a long shot.

[Alex Hayley]

Originally Posted by baclay9

Looks like a pretty even split between 2.5" and 3" pipe. Is this like a edelbrock vs. Holley argument?

Smaller exhaust producing more torque is a very generalised statement that can be correct if the motor is small enough. If the motor is big enough and flows well enough, a step up to 3" may be necessary. With a 454 that is quite modified, I cannot imagine that a 3" would be too big. Why don't you post the specs (heads, cam, compression, carb, etc). That would result in recommendations based on the engine.

[nomrlz]

Here's a muffler flow comparison chart. The formula for required exhaust flow is: horsepower times 2.2.
Muffler flow in CFM

OEM............................................... ...................... ...........225
Gibson SuperFlow 788200............................................ ..311
TTS Bullet Cat Converter......................................... ........324
Flowmaster 40 series 42540..........................................352
Flowmaster 50 Series............................................ .........362
Flowmaster 40 series 43040..........................................392
Dynomax Super Turbo............................................. .......410
Flowmaster 62631............................................. .............435
Carsound Cat Converter......................................... ........436
FLP Cat Converter......................................... ..................440
Edelbrock Victor 5535.............................................. ........562
Flowmaster 40 series 435409..........................................57 6
Edelbrock RPM series 5511.............................................. 579
Flowmaster Delta Force Racing 54040-10........................634
Edelbrock 304 series 5560.............................................. .640
Edelbrock Gen App 5505.............................................. ....708
Dynomax Race Magnum Welded 17216...........................711
Borla XR-1 40600............................................. ................836
Borla XR-1 40615............................................. ................854
Dynomax UltraFlow SS 17263..........................................100 0
Dynomax Race Magnum Welded 17218...........................1000
Borla XR-1 40575............................................. ................1100
Dynomax UltraFlow......................................... .................1133
Edelbrock Victor 5537.............................................. ........1400
Borla XR-1 40450............................................. ................1400
Borla XR-1 40741............................................. ................1450
Dynomax UltraFlow SS 17296, 17268..............................2200
Dynomax Race Magnum Welded 17220, 17224...............2200
Dynomax Race Magnum Welded 17225...........................2600

[baclay9]

454 bored .060 (468)
Speed pro pistons .210 dome
781 casting heads
(Considering going to 2.19/1.88 valves but haven't decided if it is worth the money yet.)
fully balanced steel crank
Comp Cams XE274H Cam
Edelbrock air gap intake
750 Holley w/vac secondaries
Sanderson 3/4 Length headers 1 7/8 primary

The heads are at the machine shop right now. He is going to cc them for me. If they are 119 cc as I suspect I should be right @ 9.5:1 compression

I also have a set of Speed Pro Pistons that are .340 dome and would put the compression @ 10.2:1. I know that would be iffy on 91 octane though and really don't want to take the chance. I figure 9.5:1 make plenty of power.

[shortbed70]

Originally Posted by baclay9

Can yu keep them somewhat quiet if you are trying? Like say taking off from a stoplight with a cop sitting beside you? Are they just really loud when you punch it? How is the in cab noise? Can you listen to the radio ect...
Posted via Mobile Device

I really don't know cause I haven't drove my truck in almost two years. I would think they shouldn't be any louder than a short glasspack at mild throttle but get into it and they sound like open headers without the popping. They have several kinds I got the loud ones they have some that are quieter and louder.
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[baclay9]

Originally Posted by baclay9

454 bored .060 (468)
Speed pro pistons .210 dome
781 casting heads
(Considering going to 2.19/1.88 valves but haven't decided if it is worth the money yet.)
fully balanced steel crank
Comp Cams XE274H Cam
Edelbrock air gap intake
750 Holley w/vac secondaries
Sanderson 3/4 Length headers 1 7/8 primary

The heads are at the machine shop right now. He is going to cc them for me. If they are 119 cc as I suspect I should be right @ 9.5:1 compression

I also have a set of Speed Pro Pistons that are .340 dome and would put the compression @ 10.2:1. I know that would be iffy on 91 octane though and really don't want to take the chance. I figure 9.5:1 make plenty of power.

Wanted to bump this with my engine specs one last time for last minute opinions. I am ordering mufflers soon. I talked to the guy at the muffler shop and he acted like I was crazy for even considering 3".

[Alex Hayley]

Unless the guy at the muffler shop has alot of experience with high output engines, I would ignore his opinion and look to the guy who is working on your heads and your engine.

How big are the intake runners in your heads? I don't know chevy big blocks very well.

If you just want to make a quick decision, I don't think you would be crazy going with 3" but it might not be very necessary though.