2 inch exhaust with 300+ hp 5.7

[YukonKyle]

Hi Everyone, posting this question here as well as the tahoeyukon forum.

Is anyone running 300+ hp through 2 inch down pipes?


I have a 97 Yukon with the MPFI upgrade and just recently the 0411 pcm with the Vortec express van tune. what a difference that made! increased mpg by 3 and the engine feels more alive.

Anyway... back to the exhaust kit. I mistakenly bought the Magnaflow 23453 cats & pipe kit thinking it was 2.5 inches, but it is only 2 inches. Still ok with the stock 255 horsepower Vortec 5.7, but I am planning a camshaft swap in the near future. I already bought the cam, it is the SPO 350/357 crate engine cam from Chevrolet performance part number 12677151.

Camshaft Type (P/N 12677151): Hydraulic roller
Camshaft Lift (in): 0.473" intake / 0.473" exhaust
Camshaft Duration (@.050 in): 215° intake / 223° exhaust

So, maybe it isn't going to achieve GM's 357 hp, but it will be over 300. If you look at all the exhaust charts 2 1/4 is the lowest I should go.

SO should I ship it back? It seems there are few other bolt on solutions.

 

[Supercharged111]

Ship it back and get some headers and do a full exhaust. That makes as much difference as the cam.

 

[sewlow]

I'd be leanin' towards the 2.5".
With an 'H' pipe.

 

[Supercharged111]

I'd be leanin' towards the 2.5".
With an 'H' pipe.

That or an x. They're about equally effective on the dyno. H does a little more down low, x a smidge more up top but adds more to the sound. Not the noise level, rather it gives a higher pitch when you lay into it. Or could do a y pipe with single 3", it too benefits from scavenging, but the duals would be ideal.

 

[PlayingWithTBI]

I have 2-1/2" shorty headers and a JBA mandrel bent Y pipe into a 3" high flow cat and 3-chamber muffler (nice low rumble). I'm thinking my motor is close to 350HP (best guess). I think I might gain some with a dual exhaust system but I have to pass inspection/emissions here.

 

[YukonKyle]

Thanks for all your replies! So yeah it is heading back.

I do want to keep cats and all my 4 sensors. I already have a big magnaflow muffler with 2.5 dual in and 3 inch out. I’d like to keep that.

I was also trying to avoid a custom exhaust due to the high cost.

Suggestions are welcome! Thanks

 

[b454rat]

Gonna have to go with 3/4 or 1 ton down pipes. Summit n jegs only sells the smaller pipes, I looked for the bigger n doesn’t matter size, it’s all 2 1/4”.

 

[YukonKyle]

Gonna have to go with 3/4 or 1 ton down pipes. Summit n jegs only sells the smaller pipes, I looked for the bigger n doesn’t matter size, it’s all 2 1/4”.

Nobody posts what size their pipes are, I have been looking through rockauto at K2500 cat kits and its all a guess...

Maybe the jegs off road can be used, and then weld in some highflow cats?

 

[b454rat]

I have the jegs pipes, should be very easy to weld cats in.

 

[Supercharged111]

The 2500 trucks had bigger head pipes and bigger cats stock. They're about 2.5" at the manifold, but flare up to 3" leading into the cat and back down to 2.75" post cat.