Hey everybody I have a 1998 2500 5.9. I was wondering how much I'm really going to get out of these headers. I have a spectre cold air intake. Let me know if u have used these headers before or if u have a 5.9 with shorty headers.

 

Not very much unless you address the Y-pipe as well. The Y is actually the biggest restriction in the exhaust....

 

Just getting a better y-pipe would yield more power then headers with a stock y-pipe

 

 

maybe 5 hp.

 

Where or what type of y-pipe should I get? And how big?

 

I would say the Best bet would be to go to a local muffler shop and have them fab you one up.

 

No smaller that 2 1/2" inside diameter. I think stock is 2 1/4"....3" may be too big, and maybe not. Someone that is more experienced in exhaust may chime in and enlighten...

The key is to remove the factory built choke point to allow exhaust gasses to move.

 

I always figured 2.5" at the collector all the way until they merge into one, which I would then make 3" all the way from there back, would be most beneficial with flow. 3" just seems too big from the manifolds.

 

Well You would have gotten the same amount of power and lifespan as if you went with the much cheaper stainless clones... And then you could have taken that extra 200.00 bucks or so you saved and used it towards some other performance mod and been further ahead... like 1.7 roller rockers which would have given you 3 times the performance gain...(4 times with headers and RR's)

Only longtubes would have any real benefit over shorties... and that depends on the rest of the setup too..