Exhaust system questions

[TommyD11730]

Ok guys so here goes....
84 GMC K2500, bone stock 350 4V w/700R4.

I currently have a bone stock exhaust system. Air tubes (no air pump), heat riser (actually works!) you name it.

I would like to try and free up the exhaust flow some. Trying to stay away from Headers as a decent set cost $$$. Figure the cheap sets rot out/leak and I'm a little old for that.

So I take note it looks like the Y pipe has a 3" outlet on my 91K5. I could deal with a single 3" exhaust. Problem however is I'm thinking no way will that Y pipe for a K5 fit my K2500, especially with the heat riser. Little more looking around shows the 87 TBI trucks also used a 3" Y pipe.

Best guess is to run the TBI 3" Y pipe I need to run the TBI exhaust manafolds? (plug the O2 bung).

Any ideas?? Just trying to get a decent exhaust on the cheap.

 

[76zimmer]

Until you change manifolds IMO your gains will be negligible. Try some of the aftermarket Rams horn manifolds and tru 2-1/4" duals, then tune the engine to take advantage of it.

 

[TommyD11730]

Do the Ram Horn manafolds work on the squares?
If they dump in a unique position (stock vs LT headers) then your talking about custom exhaust. That's $$$.

 

[dyeager535]

Forget it. IMO. Headers are worth ~25hp on a SBC, and look at the complexity to get that. The problem is the manifolds. Until those are gone, nothing past the manifolds (That is not blocking flow) is worth any effort at all.

 

[76zimmer]

Im not sure if the Rams horns would work now that you question it, but as mentioned those manifolds on there now are your biggest problem with flow. And then there is the intake side of the equation.

 

[diesel4me]

Though I've never tried using ram horns on a square body,I think they might work only if you get two of the ones off a pre-73 small block that has the outlet at an angle,(used on the passenger side only I think,)-rather than straight down,a straight down outlet will most likely point directly at the engine cross member and clam shell motor mount and you'd need a very tight bend to connect a pipe to it,if you could at all...even with the angled outlets it'll be a challenge to bend the pipe to fit properly ...you may gain nothing in the end with those tight bends in the pipes..

I hate headers,all they do is leak at the heads or at the collectors,and rot away in 2-3 years around here--stainless steel ones are the best for rust resistance but they can blow out gaskets and leak just like the rest of them..

I've had stock engines with headers and never felt that big of an improvement on street driven vehicles...you need other mods to go with them,like a hotter cam,more fuel delivery,etc to gain full benefit from them..

 

[Bent77]

Had good luck using an aftermarket high flow cat and muffler

The 90s up vehicles actually aren’t terrible systems if they are 3” factory. Probably only gained 15 HP on my LT1 making those changes.

 

[dyeager535]

I hate headers,all they do is leak at the heads or at the collectors,and rot away in 2-3 years around here--stainless steel ones are the best for rust resistance but they can blow out gaskets and leak just like the rest of them..

I've had stock engines with headers and never felt that big of an improvement on street driven vehicles...you need other mods to go with them,like a hotter cam,more fuel delivery,etc to gain full benefit from them..

Cheap headers, with poorly hung exhaust, leak. I'm still considering using springs like GM did to solve the problem with flex between the engine/header collector and the frame mounted portion of the exhaust. The headers aren't the problem, even if they are cheap, thin collectors. If they were solidly mounted, with no movement, they wouldn't leak until they rotted out.

You can't just throw headers on and expect things to get better. Fuel needs to be increased, otherwise you just run lean, which isn't making more power. This is where the "engines need backpressure" myth came from. People might have burned valves after freeing up exhaust flow, but it wasn't because there was lack of backpressure...it is lack of fuel.

 

[TommyD11730]

For the price of a cheap set of headers (240$) I can replace both manafolds with 87 models and add a factory Y pipe (87) with a 3" outlet.
Advantages are should be leak proof and plug / ignition wire friendly. Also things like driveshaft / shifter linkage interference should be nill.
Single 3" exhaust out the back would be a no brainer.

Disadvantages, not much gain for the $$$ and labor expelled. (Story of my life)

I got some thinking to do!