exhaust sizing

[bigbadchev72]

I have a fairly beefed up 400 flat tops, balanced, cam, aluminum intake and carb, I am taking my truck in for exhaust next week and I was originally gonna go with 2.5" duals with H pipe off of stock ramhorns and into 2-1/4 flowmasters.

I already have the flowmasters, But I put 2.5" duals into 3" flowmasters with an H pipe on my blazer. It sounds sweet, but i lost alot of bottom end on it, It is a 350 with and rv cam.

What are you guys running on your rigs? I will not do a single pipe I want the look of duals for sure

[LuckyHenriksen]

Roll the 2.5, especially if your motor is a little beefed up. I will probably be hacking off all my brand new 2.5 X pipe and replacing it with 3 inch for the new motor

[AlienYouth]

i run 3" dual with moroso auger type mufflers, no crossover at the moment, probably do an H pipe, i like it, i run homemade silencers on the street, take em out with 1 bolt at the track

[Cunit69]

I have dual 2.5 into flow masters with no h pipe. 3" is an overkill in my opionion, but then again I have never really got any measurable results from exhaust other than sound. Just my.02

[LuckyHenriksen]

It's been tested many times that if your motor makes like 500 HP or more 3 inch pipe is better

[bigbadchev72]

Ok I already own the 2-1/4 flowmasters that i will be using on this truck.

I have 2.5" duals with H pipe and 3" flowmasters(picked them up for $80 In boxes) so thats what i used on my blazer. It had dual exhaust on it before i had it redone and it was small, I just noticed I lost alot of lowend by upsizing. Just curious what everyone else was running and there results

[texanidiot25]

Headers and bigger pipes create less back pressure which open up top end power while sacrificing low end torque. Even as much as tossing a glass pack in place of the suffocating "muffler" on my Firebird opened up it's top end a good bit... but it never had any noticable drop in the low end.

I'll have a drive soon enough to see how my truck goes with 2-1/4 pipes

[chris71]

with stock ram horns i would bet that it wont matter 2.25 versus 2.5, if you really want to let her breathe better, you need a set of headers. ever hear the phrase "a chain is as good as its weakest link" i think exhausts are the same way, it doesnt matter if you have 2.5 feeding into your 2.25 mufflers, because the flow will get restricted and slowed down at the 2.25. i would probably just get 2.25 from the manifolds into the 2.25 mufflers, even so, your not getting the full benefit of the bigger diameter pipe because the manifolds are restricting it right from the start. dont get me wrong, the 2.25 with manifolds will help over stock. LuckyHen... is right, 3" on a 400HP engine lets say, will probably loose back-pressure, which helps get the exhaust out of the engine, so it would most likely hurt you if you run 3"

[Sport/Truck]

Originally Posted by LUV2XCLR8

This is thread #1,000,000,000,000+ on Exhaust questions and I'm not even
going to put my dog in this fight, however I always post this chart to helpout
others here, it is out of the Dealers Part book for Flowmaster products, cya

Here you go.
s/t

[chris71]

that is a neat chart, seems to make sense to me, thanks S/T