Exhaust systems
 

I need to replace my exhaust system soon. All I can find is 2.25" exhaust. I was hoping to go with a 3" system, since I think that 2.25 is wayyyy too small for a 400 sbc. Is it possible to find any after market systems that are 3"?

Re: Exhaust systems
 

Doesn't summit offer one?

Also have you taken you truck to a shop who does custom installs? This way you can get a wider selection of mufflers.

Re: Exhaust systems
 

Well it gets pricey fast but I mean I tried to find a full system that I wanted ended up buy mufflers that were 3' in and 3' out and had an exhaust shop just do the piping.

Re: Exhaust systems
 

I don't think you are losing anything with a 2 1/4 inch system. Headers and a single three inch system would prolly be the best for horsepower numbers, but prolly only a few more ponies 2 1/2 duals. 2 1/2 duals prolly make more power than 3 inch duals. Not to mention the packaging issues that come with using 3 inch pipes.

Re: Exhaust systems
 

Actually, Dual 3" is wayyyy to big for your 400! For 3" duals you better be paicking a big, big block at over 500hp.

http://www.exhaustvideos.com/faq/how...pipe-diameter/

Re: Exhaust systems
 

Really? I see the newer 2500HD silverados and their exhaust looks huge for a 6 liter. My neighbor drives one and the pipes on his truck look massive compared to mine. So I figured if my truck has a higher displacement, that it would be better with bigger pipes. So would a 2.5 work? I just think that 2.25 seems way too small for a 6.6L gas job.

Re: Exhaust systems
 

Cubic inches has nothing to do with what size exhaust you have.... your buddys truck has a new motor that will eat yours alive. You have to have force to push the gases out; with a dual 3in system you need to have one stout engine. Go with a duel 2.5 in. with a crossover pipe and that will give you good sound and added performance. If your sold on a 3in spend the money and find out why its not very good for the application. ...
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Re: Exhaust systems
 

Well stated. That 6.0 is putting out prolly twice the power the OP's 400 is making. Plus a lot of the newer trucks use double walled pipe (pipe with in a pipe) to keep noise down, so that make the pipes look larger than they actually are.

Re: Exhaust systems
 

Your neighbor's truck is not a true dual 3"(if it has twin exhaust pipes).

A single exhaust in 3" will be fine, but if you are going duals, 2.25 to 2.5 will be more than adequate for your engine.

Re: Exhaust systems
 

Cubic inches factor in no mater what. And since the OP didn't post specs of his engine we can't say weather 3" is to big or not.
There's such thing as too small for exhaust but no such thing as to big, just inefficient at certain Rpms.

A 2.5 system accommodates a great range of engines for the street. A 3 in system can lose you as much as 25ftlbs at the low range of rpm but give that back at the top end.

There's a lot of factors that effect how a SYSTEM of exhaust works other than flow potential. Headers vs manifolds collector length tailpipe length. Balance tubes x pipes. Millions of mufflers. Firing orders, engine size, port size etc etc
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Re: Exhaust systems
 

My brother ran 2 1/2's straight back off his mostly stock 400 w/ quadrajet setup (1977 K10). I've heard those are really better motors for torque anyways, so I'd retain the low-end if I was you. Brother was really happy with the 2 1/2, great sound and power, no install issues. Good luck!

Re: Exhaust systems
 

He said it was a 400sb. I agree that my statement was wrong, but I meant to say that the op needs to pick a exhaust system on his needs and not assume that bigger needs a really big exhaust. With a 400 id treat it the same as a 350 on the stock levels.
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Re: Exhaust systems
 

On stock levels definitely. At which I wouldn't hesitate for a 2.25 system. Pipes also has some good 2.5 x pipe systems as well
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Re: Exhaust systems
 

looks like my question has been answered. I think I will start to search for a good 2.5 inch system. I already have an idea for what mufflers I want on too.

Re: Exhaust systems
 

2 1/4 inch dual systems should be outlawed min for any SBC above a 305 should be min 2 1/2, or a single 3 inch system. its all about scavenging the exhaust, you want the prior exhaust pulse to pull the next one out of the chamber so you and get more air and fuel in for the next cycle.

Re: Exhaust systems
 

Good that you decided. That said, you may find the 2-1/4" is more prevalent (and less $$).

Maybe a couple points that may have been missed. Factory was what? A single 2"? Muffler that was designed to be quiet and fit, not produce max flow numbers on a dyno. Are you regular cruising at 5k+ rpm?

K series truck. Unless the exhaust hangs way down, it's got to fit between the transfer case and frame.
Factory duals for my big block are 2-1/4 or less. The General may have been off on exhaust sizing, but the money they spent to do it would prob finish all my trucks in my lifetime.

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yea and that 2 inch single really helped choke down an already miserable engine in almost any size. add to it the pellet style convertor in the late 70's and you had a recipe for Sucksville pie.

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If I can't find the 2.5 I will go with 2.25, They just looked tiny for the truck so I figured they needed to be larger. Maybe I will just get some bigger tips on the end for a sharper look and sound. I just want my leak gone and a mean sounding exhaust by next year when I have more money and time to do it. Pretty hard being a student and wanting to do all these mods on a limited budget.

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take it to a muffler shop. 2 1/2 duals and some turbo mufflers should run ya $3-400. possibly less.. well worth the money for a leak free, rattle free system that looks nice out back and doesn't hang down all ****ty.
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Re: Exhaust systems
 

I've had 400's for the last 20 years or so. On a stock 400 I would probably go with a 2.25", On a mildly built 400, cam, headers, 4barrel, 2.5", on a real healthy 400, I would go 3". I currently have a 406 with 10.75 compression, mechanical roller.580 lift cam, Victor Jr heads,and a Pro Systems 830 carb. I'm running a mandrel bent 3" with Dynomax super turbo mufflers and an X- Pipe. This exhaust works real well with my setup. I had it on my older mild 400 and I lost some bottom end torque, but I was planning on building my current motor, and didn't want to do it twice.

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both my 78 and 79 are dual 2.25
yes it's a smaller block ,but my stock pipes were 2.5 not 2"

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I'm shocked how much exhaust shops are 300-400 for glass packs and exhaust is crazy to me for my c10 I got 2 1/2 from headers into flowmaster delta race 40s with hangers and turndowns for 100 bucks out the door
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where !?

Re: Exhaust systems
 

Man if i can just get 100 bucks to the axle i'd drive there!!! Lol
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