2.5" vs 3" pipe size for high powered FE; which is better?

[robroy]

Good morning,

It seems that the two potential choices for exhaust pipe size for my high powered FE project are 2.5" and 3".

As I understand it, 2.5" will provide more low RPM torque, less high RPM flow, and less noise.

And 3" will provide less low RPM torque, more high RPM flow, and more noise.

Naturally this choice is a matter of preference, but what are your inclinations and why?

My initial inclination is to go with 2.5" pipes, since I like quiet and I'm thinking of using Borla mufflers (which only seem to come in 2.5").

Thanks very much!
-Robroy

[robroy]

Sorry about the truncated subject line. I'd intended it to read, ``2.5" vs 3" pipe size for high powered FE; which is better?''

[sideoilerfe]

If you go duals, then 2.5.

Honestly, I think a 2.5 into a single 3 is your best bet for lowend torque but your exhaust alone isn't going to give you noticable power unless your motor is at least mildly built.

On a stock motor like a 360, you have a single 2 inch tailpipe. I changed mine to a 2.5 because it didn't like going over 70. That made a noticable difference at about 55-60 MPH but in the lower RPMs it stayed the same. If I would've went to Dual 2.5 with Borla or Dynomax mufflers, I would've gotten the same results.

I had a 65 F250 Camper special with a 352. When i bought it It had an exhaust leak from hell and the manifolds were broken. This engine ran great! it had plenty of power. People thought I had a 390. I was 19 at the time and thought, "I'll put headers on it and I'll have even more power." SO, I put headers on it and 2.5 duals and Dynomax mufflers and it sounded so much better but it made NO difference at all in performance.

Unless your engine is pushing 350+ HP, a fancy exhaust isn't going to make a big difference.

[robroy]

'Evening Sideoilerfe,

Thanks for the reply! The motor is a 400HP FE I've ordered from Proformanceunlimited. It'll arrive in about four weeks so I'm trying my best to prepare for it in advance.

Would you say dual 2.5"s is the best choice for this setup?

Thanks!
-Robroy

[td]

i put 3'' pipe on a stock 360 one time before i learned any better, and it absolutely killed the bottom end power. in my opinion 2.5 inch pipe is good for 400 ponies, probably even more.

[mrtleavitt]

Dual 2.5" pipes are the way to go. That's what I run on my 390 and my brother just had a professional "X" style exhaust built for his radically built 390. The owner of the exhaust shop explained it to us and that's the best setup he said. He runs it on his 600 hp chevy as well. 3" dual would be over kill and non-profitable. If you are going single, then the 3" would probably be better, but I say duals all the way!

[rubiranch]

I don't really know which one is best.

I installed a new cam and a set of Heddman Hedders. I chose a 2 1/4" Y-pipe into a single 3" exhaust. I chose a Magnaflow muffler and a mandrel bent tail pipe than exits just like it did when it was stock

I am 100% please with the sound and performance. I have no idea if 2 1/2 dual would perform better but I was told if it did I couldn't tell the difference by the seat of my pants.

I would think that 3" duals are too much for a 390.

[F10YRB12118]

robroy,

Great questions, same one I was starting to mull over.

What kind of 400HP FE motor did you order from Proformanceunlimited? 360, 390, 410, etc.?

I'm working on rebuilding my 360 and I'm learning all sorts of good stuff from your post.

Have you decided what brand of header yet? I have Hooker Comps on my Bronco 302 and they're nice.

Yours,

[robroy]

i put 3'' pipe on a stock 360 one time before i learned any better, and it absolutely killed the bottom end power. in my opinion 2.5 inch pipe is good for 400 ponies, probably even more.

Hi Td! Does this mean you put on a single 3" pipe or dual 3" pipes? And about the 2.5" pipes, do you mean single or dual?

Thanks very much!
-Robroy

[robroy]

Hi Mrtleavitt and Rubiranch,

Thanks for the advice! It seems like dual 2.5" are the best choice. And this makes things simpler because the Borla Turbo XL mufflers come in 2.5".

-Robroy

[robroy]

robroy,

Great questions, same one I was starting to mull over.

What kind of 400HP FE motor did you order from Proformanceunlimited? 360, 390, 410, etc.?

I'm working on rebuilding my 360 and I'm learning all sorts of good stuff from your post.

Have you decided what brand of header yet? I have Hooker Comps on my Bronco 302 and they're nice.

Yours,

Hi F10YRB12118! Thanks for your reply; it's nice to know I'm not the only one benefiting from all the great advice that I receive!

This is the 390 motor I bought from Proformanceunlimited, with a few minor upgrades (Edelbrok high flow water pump, Moroso oil pan, and Ford "Cobra" valve covers):

http://www.proformanceunlimited.com/spe ... 425hp.html

I haven't picked out the headers yet. Steve at Proformanceunlimited recommended Hedman headers to me on the phone, but I was planning on starting a forum thread about headers (if I can't find one burried in the forum history somewhere). Thanks for the recommendation on the Hooker Comps; I'll check those out.

As for the rest of the exhaust, it seems that Borla Turbo XL mufflers and dual 2.5" pipes (mandrel bent) is what I'm looking at.

Thanks F10YRB12118!
-Robroy

[sideoilerfe]

i put 3'' pipe on a stock 360 one time before i learned any better, and it absolutely killed the bottom end power. in my opinion 2.5 inch pipe is good for 400 ponies, probably even more.

Dual 3" is overkill, I agree. But single 3" or dual 2.5 with an "X" if you've got the ponies for it.

[robroy]

Good morning Sideoilerfe,

What's an "X?" And is 400HP sufficient ponies for an "X?"

Thanks!
-Robroy

[Redcap]

Good morning Sideoilerfe,

What's an "X?" And is 400HP sufficient ponies for an "X?"

Thanks!
-Robroy

That is an X pipe.

[robroy]

'Morning Aaron, thanks for the photo (worth a thousand words)!

Why are these gadgets desirable?

Thanks again,
-Robroy