Author Topic: Factory or bigger (Read 1942 times)

Sleepychallenger · « **on:** June 22, 2014 - 04:26:40 AM »

So I have factory size exhaust (don't know what size that is)....if/when I go to headers should I keep the pipes or increase the size. And which should I do first

Bullitt- · « **Reply #1 on:** June 22, 2014 - 09:42:50 AM »

From what I understand for a street car headers gain you no appreciable performance and the headaches are numerous.
Stock exhaust is 2.25", most folks move up to at least 2.5" as that's what most aftermarket kits offer and may gain some performance. Other than Accurate Exhaust and other reproduction systems, which seem to be the priciest option, I don't see many 2.25".

Sleepychallenger · « **Reply #2 on:** June 22, 2014 - 11:11:54 AM »

I wasn't sure if I would get a noticeable gain by going to headers and 2.5's since I'm going with the new heads and eddy perf rpm intake.

brads70 · « **Reply #3 on:** June 22, 2014 - 12:08:20 PM »

Is the engine stock?

Sleepychallenger · « **Reply #4 on:** June 22, 2014 - 09:53:54 PM »

It has a 30 overbore, and a hemi grind cam. I will be putting on the stealth heads and RPM intake when I get home.

brads70 · « **Reply #5 on:** June 22, 2014 - 10:22:27 PM »

I like 2 1/2" exhaust big enough to breath but doesn't drone like 3" can. I'm using the magnaflow stainless system and love it! We just installed Dougs headers on Andys Cuda . I was REALLY impressed with the fit and finish. Much better than the headmanns I'm using . The key is using the good copper gaskets that don't blow out like the paper ones do. IMO

Sleepychallenger · « **Reply #6 on:** June 22, 2014 - 11:11:20 PM »

Quote from: brads70 on June 22, 2014 - 10:22:27 PM

I like 2 1/2" exhaust big enough to breath but doesn't drone like 3" can. I'm using the magnaflow stainless system and love it! We just installed Dougs headers on Andys Cuda . I was REALLY impressed with the fit and finish. Much better than the headmanns I'm using . The key is using the good copper gaskets that don't blow out like the paper ones do. IMO

Thanks. The dougs will be a couple years down the road with the pricing there, but if they are that nice then they will be worth it. Do you think it is something that can be felt?

brads70 · « **Reply #7 on:** June 23, 2014 - 06:20:12 AM »

Quote from: Sleepychallenger on June 22, 2014 - 11:11:20 PM

Thanks. The dougs will be a couple years down the road with the pricing there, but if they are that nice then they will be worth it. Do you think it is something that can be felt?

Not sure? I'd guess it adds 20-30 HP at least depending on the engine combo?

Bullitt- · « **Reply #8 on:** June 23, 2014 - 06:48:54 AM »

This is on a 340. On top chart phase-3 added headers, you can see max HP increase around 20 HP at 5800RPM.
Down where we drive 2000-4000 rpm the increase is 10-15.

On the street torque is where it's at, similar results on bottom chart +10-20 in lower RPMs

Chryco Psycho · « **Reply #9 on:** June 23, 2014 - 11:12:40 AM »

Quote from: brads70 on June 22, 2014 - 10:22:27 PM

The key is using the good copper gaskets that don't blow out like the paper ones do. IMO

As well as thick flanges that will not warp .

As stated before Backpressure is not good But Velocity is very important if a combo is well tuned more air is pulled into the cylinders with scavenging using headers than the pistons pull in , this is where the hot air leaving at high speed creates a vacuum behind it pulling air into the cylinders with the exhaust & intake valves are both open during the overlap in the cam , at high rpm this can actually create mild supercharging where the cylinder can be filled to more than 100% volume . Manifolds do not have runners long enough to effectively create scavenging .
If the exhaust is too large the speed is lost inside the exhaust , too small & it becomes restrictive where the speed needs to be excessive & causes the engine to work harder to push the exhaust out so it is a balance .

dfrazz · « **Reply #10 on:** June 27, 2014 - 11:29:20 PM »

FWIW - I recently read this article in HOT ROD Mag on the proper size of pipes related to the engine output and displacement. I went with 3" TTI H-pipes on my 408 stroker that did 463 HP on the dyno.

Exhaust Pipe Sizes For Street Performance
Pipe OD (in)     Power (hp)   Engine Size (CI)
Single   Dual
2.0     2.0     100     150�200
2.25     2.0     150
2.5     2.0     200
2.25     2.0     150     200�250
2.5     2.25     200
2.5     2.0     250
2.5     2.0     200     250�300
2.5     2.25     250
3.0     2.5     300
3.0     2.5     250     300�350
3.0     2.5     300
3.5     2.5     350
3.0     2.5     300     350�400
3.5     2.5     350
4.0     3.0     400
3.5     2.5     350     400�450
4.0     3.0     400
4.0     3.0     450
4.5     3.5     400     450�500
4.5     3.5     450
4.5     3.5     500-and-up

Read more: http://www.hotrod.com/techarticles/1407_what_exhaust_pipes_work_best/#ixzz35tuFaM2S

Author Topic: Factory or bigger (Read 1942 times)

Sleepychallenger

Factory or bigger

Bullitt-

Re: Factory or bigger

Sleepychallenger

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brads70

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Sleepychallenger

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brads70

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Sleepychallenger

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brads70

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Bullitt-

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Chryco Psycho

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dfrazz

Re: Factory or bigger