Exhaust pipe size

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MoparFan

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Hi,

in the next weeks (hopefully in 3-4 weeks), I will have to have the exhaust completely redone.

I want it to be dual, as no header, it's a 318 2-bbl...for now
This summer I will install a 4-bbl (unknow carb, with a Edelbrcok performer intake most probably).
the future plan is to install a mild 360 (350-400hp)...
So what size of exhaust should I go for, 2.25 or 2.5...won't be mandrel bent.

Should I have one made for the 318, and then when the 360 is in, a new exhaust?

What is the effect of a too large exhaust (i.e: dual 2.5 for a 318)?
 
I'm running 2.5 on my 350-400hp 360.

So that would be my 2cent on when you get the 360. But for the 318. I don't think there is a major problem if the exaust is a little big on it.
 
I got a 71 duster with a stock 318 2bl and I run hedmans with 3 inch pipes all the way to my 3 inch 40 series flowmasters. I have had no problems and it sound awsome
 
Plan for the future..use 2.5" pipe. the only issue may be the flange on the driver's side manifold..getting a 2 1/2 " pipe to the 1 7/8 hole can be a pain..so your exh guy may go smaller right at the manifold, then go to larger pipe. If you are running headers in teh future, this is no big deal..if you are going manifolds the whole way, it's a big deal..
 
i would use 2 ½" when i make systems for 318s wee usuly make the first piece in 21/4" then as son as posible a step up to 2½" then there is no big problems
 
I Would Get The Headers That You Plan To Run W/360 And Put Them On And Have Your Exhaust System Made. This Will Also Help Out The 318 When You Do The 4bbl. You Can Get Good Headers From Summit For Around 100 Bucks(the Summit Brand). Exhaust And Headers Are A Pain In The Rear Do It Once And Get It Over With.as For Size Deffintly 2.50
 
well it looks like 2.5 would be the way to go....so 2.5 it will be.

As far as for headers, i'm really not sure what to do. Headers like Hedman (let's call them the affordable one), are a major pain to install and, from what i have read, have some clearance problem to ground.
So I tought that I would wait until I can afford a set of TTI, wich is not for now.
Will there be a good performance gain, even with these "affordable" headers?

...the other thing, is that yesterday I discovered (i'm newbie) that to install a big block you need a kit, like Schumaker, to swap, and that mostly it (well plus a couple of other thing a guess, but still...)!!! So will it be 383/400 8):D or a 360 ... i will have to think about that also.
 
The 2.5" pipe won't hurt the performance of the 318 and you wouldn't see any improvement either over the 2.25". Everything else being equal the 2.5" system will be a little lounder than a 2.25" system.
 
Does anybody have any dyno experince with this? 2.5" Duals seem a bit large but I am just guessing. from 4/6 cyl experiance you can see a big loss on an exhaust with an exhaust that is too large. On the Rally car we saw a 14 horse loss with a 2.5" exhaust 232hp @ 9000 vs 218 @ 9000 at the wheels this is on a 2.0L 16v DOHC BIG individual Trottle Body intake two injectors per cyl. Move a Lot of air any ways in theory the 2.5 was going to help on the top but didnt produce.
 
Just the butt Dyno test. I went from 2.5" to 3" on my pretty mild 340 and didnt notice any lose in torque.
 
Ok, so i'm pretty sure now that i'm gonna stick with the smallblock anyway, so I think of buying a set of header and to go with dual 2.5".

About the headers, in the affordable category wich one is the best fit/easiest (not easy I know) installation? Hooker/Hedmann/other???
By the way, I would like to keep my power steering and power brake.

Thanks again
 
Most of the cheaper $100-$200 headers are pretty much the same design. None of them fit great.
 
my old flowtech headers where ok for the price, but none of the cheap are realy good as addam said..
 
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