Exhaust 3 Inch Exhaust

[GoldenEagle91]

Hi guys,

I am in the early stages of planning for the exhaust that I would like to do on my 306 when I finally get it installed and I wanted to know if anyone had any experience or input on the matter of going with a 3 inch exhaust all the way out. My plan was to pick up summit racing headers ( http://www.summitracing.com/parts/sum-g9030/overview/make/ford ), their 3 inch exhaust pipe kit ( http://www.summitracing.com/parts/sum-670147 ), and Flowmaster super 44 mufflers ( http://www.summitracing.com/parts/flo-943045/overview/ ). The car will be a weekend driver for the mean time and I plan to eventually do some drag racing with it so noise isn't a real concern. Please let me know if you have any experience with doing a similar setup or if you know of anyone who has done it and their results.

Thanks,
Andrew

 

[A5literMan]

No expierience with those parts. Just a fwiw a 2 1/2" exhaust is more than enough for 450-500hp. Also 3" tails can be a problem with most cars. They tend to hit on the fuel tank and/or suspension parts.

 

[liljoe07]

I went from 1-3/4" equal length shortys and a full 2-1/2" Flowmaster system, to 1-3/4" long tubes with 3" spintechs and 3" straight pipes. This was on my 302. I didn't notice anything substantial. But it's a daily driver. Biggest difference was no drone.

I've got the same 3" system on my 347 now.

 

[f8tlfiveo]

I think you stick with 2.5.... I think 3" looks ricer unless you have the motor to back it up.. Plus like previously stated 2.5" is plenty big


Sent from my iPhone

 

[Mustang5L5]

Horsepower goals??

2.5" is enough for most daily driver type cars with modest power. Anything more and you run into issues with pipe clearances and banging on the gas tank.

 

[GoldenEagle91]

Thank you all for your input. I guess I was just aiming to have the best flow possible and that is why I was planning on 3". I am hoping to break into at least 400 at the flywheel but I guess we will see. It sounds as though 2.5" will be plenty for what my goals are though from what most of you guys have stated. I was a little bit nervous about potential clearance issues near the gas tank as many of you have stated. I suppose its going to be 2.5" after all cause 3" doesn't sound like it would benefit me enough to warrant the extra money for the exhaust pipe.

 

[madspeed]

No expierience with those parts. Just a fwiw a 2 1/2" exhaust is more than enough for 450-500hp. Also 3" tails can be a problem with most cars. They tend to hit on the fuel tank and/or suspension parts.

actually 3" tailpipes give a bit more clearance due to the routing. They go under the front corners of the fuel tank as opposed to around them like 2.5" pipes do

 

[7991LXnSHO]

Horsepower goals??

2.5" is enough for most daily driver type cars with modest power. Anything more and you run into issues with pipe clearances and banging on the gas tank.

2.5" duals are plenty for much more displacement than 302 cu in.
The Dronemasters will flow plenty with plenty of noise. Unless you are going to big block displacement or a lot of turbo, you will be fine. Too big of pipe can even cost torque from flow velocity issues. Save the weight, and make sure you have a cross over pipe, X or H.

 

[GoldenEagle91]

actually 3" tailpipes give a bit more clearance due to the routing. They go under the front corners of the fuel tank as opposed to around them like 2.5" pipes do

I guess it would be cool to see an undercarriage shot of the routing for a 3 inch exhaust setup to get a better idea of how it would have to be set up.

2.5" duals are plenty for much more displacement than 302 cu in.
The Dronemasters will flow plenty with plenty of noise. Unless you are going to big block displacement or a lot of turbo, you will be fine. Too big of pipe can even cost torque from flow velocity issues. Save the weight, and make sure you have a cross over pipe, X or H.

I think upon further investigation that I am going to go with the slp lm1's again. I had them on my other fox before it was stolen and they sounded pretty sweet through straight pipes. It really didnt drone at highway speed either which was nice cause like you said about the flowmasters, they tend to drone pretty bad. My dad has a super 44 muffler on his ram with a hemi and drone it does.

 

[GoldenEagle91]

does anyone have any experience with hedman hedders? They appear that they will have better flow than the summit units based on the photo from hedman's website. Standard Duty Uncoated Hedders .

 

[mikestang63]

2.5 inch gives you a total of 5" in exhaust- more than enough to support 600hp. I think 3" is overkill and can actually hurt performance as it will have lower backpressure, reducing torque..

 

[GoldenEagle91]

2.5 inch gives you a total of 5" in exhaust- more than enough to support 600hp. I think 3" is overkill and can actually hurt performance as it will have lower backpressure, reducing torque..

Is there some sort of information regarding how many inches needed for supporting a certain amount of horsepower somewhere? I'm curious just so I have a reference down the line. Thank you for the info!

 

[mikestang63]

Is there some sort of information regarding how many inches needed for supporting a certain amount of horsepower somewhere? I'm curious just so I have a reference down the line. Thank you for the info!

The complete performance exhaust system. An explanation on how to setup the exhaust system on your street rod.

 

[GoldenEagle91]

The complete performance exhaust system. An explanation on how to setup the exhaust system on your street rod.

Great information my friend. Thank you

 

[liljoe07]

2.5 inch gives you a total of 5" in exhaust-..

That's way off in terms of area. Dual 2.5's is no where close to 5".

 

[mikestang63]

That's way off in terms of area. Dual 2.5's is no where close to 5".

really- tell me how I'm wrong. On a dual 2.5" ehaust system, how is that not 5" of total exhaust. I guess Flowmaster, Dynomax, and every other exhaust company is wrong as well.

 

[liljoe07]

Compare the area of 2- 2.5" tubes vs one 5" tube. Its not even close.

 

[madspeed]

I concur

 

[hoopty5.0]

I have 3" VRS tails. They do rattle in places. I recently got a few of them fixed, but it still hits on the UCA mount on the body and rattles sometimes. Excuse the dirt, it's been raining like crazy.

 

[90lxcoupe]

3" exhaust will not have any noticable drawbacks in performance in a 400 hp application and it may be a smart idea to do the 3" now if you plan to make more power later. If you think there is any chance you will be using nitrous just do the 3" exhaust. There is no magical number where a 3" exhaust is needed. There are so many factors to this that it would be nearly impossible to test because one camshaft could have exhaust timing events that favor the bigger exhaust and one could favor the smaller exhaust.

Here is something to really consider though, and a reason i like the summit universal X-pipe. When you have a mid pipe, the merge section will actually add collector length to the headers. The placement of the X is very important and i believe that placing the X as far forward as possible will help the combination as a whole because when you have the x or h joint way back near the mufflers you have all kinds of collector length added for no reason. I think the exhaust pulses should be equalized ASAP. Also, the exhaust will sound much better with the X closer to the collector.