exhaust

[bhuddah]

has anyone ever taken a die grinder to the inside of a stock exhaust manifold and opened it up inside to match the round opeing from each port? It looks like they just cut a slot in the main tube and welded on round ports causing each one to be almost half the size it could be, might save on the expense of at least $600 for headers?
what ya think?

 

[cypherbane139]

yeah it will free up some ponies, but dont expect the same performance out of them that you would expect from headers. a good set of tuned headers are designed to create a vacuum, pulling the exhaust out of the combustion chamber.

i suppose it depends on what you are going to do with the engine. personally i wouldnt have headers on my 2.8 if the previous owner hadnt already installed a whole new exhaust setup. (albeit it does sound freaken awsome )

 

[Oreif]

Yes, This is a common modification. Remove the exhaust manifolds, weld a seam on the outside and port the inside. Next take the crossover pipe and have an exhaust shop cut out the "Y" and port that as well. (GM crushed the pipes so they fit into the "Y") When all done you will gain around 7-8 horsepower. Add in a good muffler, and slightly larger pipes with a catco hi-flo cat you can then gain around a total of 12 hp.

Go to www.fierostore.com and buy their big bore throttle body and this will add another 2-3hp.

 

[bhuddah]

I thought it would help some as the factory really constricted the factory manifolds. good hint about y pipe, I've been staring at it as I go through all these parts. I'm getting ready to put a good running 2.8 into my '87 GT which died. the replacement motor is out of another one I had, it's a stock motor but just looking to do some minor things to it before it while it's on the engine stand. Replacing all the hoses, belts, plugs, fixing exhaust, might clean it all up and re-paint and powdercoat the block, brackets etc... I also have a complete set of brackets, heads, exhaust manifolds, intake, plenum, valve covers, throttle body you name it to sell or trade or who knows hold on to parts to do something with.

______________________________

 

[latravelingman]

I ported my manifolds and the difference was very noticeable. Also I removed the cat. and got no difference just lots of great sound. It went from a wisper to a scream so the muffler can not be very restrictive at all.