exhaust setup

[dirtautoguy]

I have a 1996 chevy k1500 with the 350 vortec that has 230,000 miles and is still going very strong. my question is a little technical but I hope someone can give me some insight. it currently has the stock manifolds and pipe/cats to the point where they bolt together. after that I have dual 2 1/4 pipe going into 2 cherry bombs and then exiting out the driver and passenger side. I love the throaty groul I have right now.

One thing that has bugged me since is the dinky 1 7/8" pipe from the headers on it. it just seems like thats way to small and its even smaller in some of the bends! so my question is how much gain would I get from replacing the dinky pipe with 2 1/4' or 2 1/2" pipe. I figure I can do it for about $150 and I also think it would be a fun project. I read somewhere that someone replaced thier exhaust with one from a 2500 truck and gained like 2 mpg. would the difference be that dramatic? I would also like to put in a H pipe but Im not real sure how much difference that would make overall. my other question is the cats would I be able to stretch the pipe on the cats big enough to fit the bigger pipe or would I be better off getting new high flow ones? any recomendations? My last question is what size collector do the stock manifolds have so I can know what size flange I need. I want to stay with the stock manifolds because of reliability. thanks guys any help is greatly appreciated!

 

[nrowensby]

No forced induction? Then you are looking at little to no gain on bigger exhaust piping...

 

[GMRedline]

The 2500 exhaust looks like a nice upgrade. I don't have the measurements though.

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I don't think you would be able to get the stock 1500 cats to fit on any pipe much larger than it is. There are some budget high flow cats out there that won't kill you in the pocket book.

Or if could find a full 2500 exhaust you could reuse those stock cats as they appear much larger than the 1500. But you take the risk that they are clogged.

You have a lot of options but there is really no way to know the exact gains. Is it worth it? That's up to you and your pocket book?

 

[dirtautoguy]

I agree! and apparently they had the bigger set on some of the 350 vortecs. from what I understand the 350 vortec should be somewhere around 255 horse power and from what I have read for a dual exhaust it should be somewhere between 2.25 inches and 2.75 inches. and also from what I have read the 350 vortecs that got the bigger pipes are like 2.75 inches with the heavier duty cats. I would hope they would both bolt right up to the same manifolds??

I am just thinkin that with the head pipes are only 1 7/8 inch pipe and even smaller in some parts when they need to be atleast 2 1/4 inches then there should be quite a restriction there. I have a pipe expander that I might be able to stretch the pipes on my cats to fit but I would have to see. I am suspicous of one that sounds loose inside anyway so maybe Ill just get new ones or leave them off. (no emissions checking). but then I would have to deal with the engine light.

if I gained 1-2 MPG from it I would be way happy! but I would have to see what it would cost in total to and see. I would love to just salvage a pipe setup off a truck but the closest junk yard is 2 hours away.... but I found a universal 2.25 exhaust pipe kit that should work for $100 depending on if the flange would fit my manifold

 

[Johnc1500]

When I changed my exhaust setup, I wasn't concerned with power I was just tired of the headers leaking/ full system leaking I ripped it all out lol, and went back with stock manifolds ordered a 3inch y pipe, and to a 3 inch inlet muffler with dual 2.5 outlet, and side-piped right before the back tire, the sound was crazy and honestly I gained more power because it wasn't leaking all the time. But I also live in Kentucky and they are not strict about Emissions or anything, so I said goodbye to the stock cat's.

 

[Mrich0908]

Changing your exhaust will also change your power band . You will gain HP up high and lose TQ down low. I would change out those exhaust manifolds first.

 

[polar]

Unfortunately I would say stick to 2" or 2.25" if you are doing anything. A dual 2.5" exhaust is usually used for 350-500hp based on what I've seen.


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[dirtautoguy]

ok thanks for the input. Im looking at going with 2 1/4 inch pipes. I also noticed the stock ones are kind of kinked on the corners as well. I want to stick with the stock manifolds because I dont want to deal with leaks and clearence issues. would I still lose bottom end power if I put smooth 2 1/4 inch pipe pretty much all the way through? I think I want to do it it would be fun, I would feel better, and if I gained 1mpg I would be happy

 

[dirtautoguy]

GMRedline is the smaller exhaust in your pic the stock from the factory? becuase those cats dont look the same as what are on my truck and I am curious if maybe they have been replaced.

 

[Chevy-Art]

Will this help you out? Look at what he did.
http://www.gmt400.com/forum/showthr...Pipe-on-a-Vortec-3%94-SI-SO-Exhaust-for-Burbs