exhaust size???

[84socal]

ok iv kinda been checking out different builds on here and lookin for exhaust kits
my question is i see alot of 2.5 in kits and 2.25 kits on here and alot of people using them

i was just wondering if any one is using 3 in and if not why not

[Jim_PA]

Originally Posted by 84socal

ok iv kinda been checking out different builds on here and lookin for exhaust kits
my question is i see alot of 2.5 in kits and 2.25 kits on here and alot of people using them

i was just wondering if any one is using 3 in and if not why not

I'd go at least 2.5". I don't think there's anything wrong with 3", especially if it's bent bent up with an exhaust pipe bender (as opposed to mandrel bends...)

Pipe size does make a difference, but it largely depends on what you have under the hood.

[70cst]

On my 402BB Curt went with 2 1/2" and said 3" would be a bad idea. I'm not sure why but he has been in the resto business for about 35 years so it was ok with me. I'll let others chime in.

[steelhorse]

Unless you are building a high reving or really big inch motor 3 ince is overkill.

[Sinister]

You'll lose a lot of low end torque with a 3" setup. Exhaust velocity will be actually higher with 2 1/2"

[69GMCLonghorn]

Listen to Sinister. The dude knows what he's talking about. I have a fairly built 350 with dual 2 1/2 inch Magnaflow exhaust with an H pipe. It is a perfect balance for the motor. If you're running single exhaust (not sure why you would), then I'd run a single 3".

Another good reason NOT to own a Ford of a similar year; try running dual exhaust on a Ford. The undercarriage is so full of crap that it's dang near impossible! Gas tank's in the way, no room in the frame rails, etc...

[gintaras]

Well I'm kind of bummed.. I just got a new exhaust yesterday and they told me that they couldn't do a 2 1/2" because the manifolds were only 2". THey gave me a 2 1/4" from the manifolds all the way back. WHy would an exhaust shop tell me this? To save $$ ??

[07SSSC]

I have dual 3" coming right off the 3" collectors straight back and cut off before the axle. Has a 383 stroker now but I figured 3" leaves me plenty of room to 'expand' down the road.

[84socal]

ok so basically my truck is gonna be used pretty much for towing its got a 402bb in it right now thats stock headers exhaust are pretty much all i want to do for now so 2.5 in exhaust would be better than the 3 in from what im seeing every one is saying
and yes pplanning on dual exhaust
next question what does an h pipe or x pipe actually do
whats the differance and how will it benifit me

im new to this v8 stuff sorry for all the dumb questions

[Jim_PA]

Like I mentioned earlier, it depends on what kind of bends are being used to make it.

3" pipe with non-mandrel bends will be crushed down to about 2.5" at the bends. Your exhaust can only flow as good as the smallest point.

[big_al_71]

Fully built 406 and I have 2 1/2 exhaust and it works perfect...
Unless you are building a full race 14:1 compression motor I would stay away for anything bigger.

[VanceH]

What is the standard size on these trucks??

[So.Cal.Super]

Here is a really good article I read about the X vs H pipe a while back.

http://www.carcraft.com/techarticles...ion/index.html

I have a mildly built 402 with full length headers, x pipe , 2.5" pipe and Flowmasters

It performs really well and gets very loud when you open it up. I also stuck the mufflers under the bed and piped it out the back to keep cab noise down.

[nightmare]

most of the difference has to do with the amount of backpressure your engine uses to be efficient. too much and you loose hp (or the engine won't run at all). too little, and you loose torque.

[Tx Firefighter]

Originally Posted by gintaras

Well I'm kind of bummed.. I just got a new exhaust yesterday and they told me that they couldn't do a 2 1/2" because the manifolds were only 2". THey gave me a 2 1/4" from the manifolds all the way back. WHy would an exhaust shop tell me this? To save $$ ??

They did you fine. Like they said, your manifolds are 2 inch. It's pointless to run a 2.5 inch pipe behind a 2 inch manifold. The exhaust velocity would actually slow down when it hit the bigger pipe. For street driving, it's better to err smaller on exhaust size. This gives much better mileage and throttle response.

[bigsnookmaster]

I run a 3" mandrel bent with an X-pipe.It works great with a 406, mechanical roller cam,Jesel shaft rockers and Victor Jr. heads. Unless you're making in excess of 500H.P., I'd go with 2.5". Remember,these are big air pumps and they do have to breathe.My .02,Good luck