Exhaust manifolds

How much HP do you lose useing stock exhaust manifolds?

Thanks
ChevyDave

Good thread – Common thought used to be that cast iron manifolds will give you a quieter engine with increased torque in the midrange RPM typically associated with street use and that headers were noisier, but certainly improve breathing at the higher RPM associated with performance and race application.

I personally like the sound of headers but have factory Corvette cast iron manifolds on my ’63 Nova running a slightly modified small block. The most desirable cast iron (factory) for SBC are the 2 ½" ram horn manifolds found on the 60's Corvettes. Good looks and good sound.

Recent article in Mopar Muscle Magazine gives some great info on crate motors with various manifold/headers. Not exact comparison with SBC, but should be close and it's a great article.

http://www.moparmusclemagazine.com/t...t/headers.html

So if I am going to be useing the truck to teter around town and occacianally pull a small boat it might be a good idea to use the stock intake manifolds.


Thanks FisherDave

One thing you will notice on that chart is that bigger is not always better and that is definitely the case with most small block Chevies.

To improve pulling power you will get a torque increase by adding a balance tube to your dual exhaust.:)

You didn't tell us what size your engine is, but I'll assume 350. For the application you're talking about, I would recommend that you go to a good muffler shop and have a 2-1/2" dual exhaust installed with a cross-over pipe (balance tube). Use Flowmaster 40 series and go as straight as possible. You can call a couple shops and get bids, but figure on spending 4-500 bucks.

If you have a big block, you can use 3" pipe but it will add to the cost.

This will give you a sweet sound and a dependable system that will last for years.

Note of caution - if you're launching you boat in salt water, make sure to keep the tips close to the rear bumper and try and keep them out of the water. They'll get real icky real fast if the warm chrome gets exposed to salt water and it doesn't get flushed off and dried .

Have Fun,
Glenn

Thanks for all of the replies I am not looking to pull anything massive its a 16ft alum. v-hull boat and its going to be launched in freshwater.Glenn you were talking about that 2 1/2 is that off a set of headers or stock manifolds or does it matter?


Thanks
ChevyDave

I'd stay with the stock manifolds and have muffler shop replace from the manifolds back. That way everything fits nice and tight.

Thanks for the info. Glenn. I believe thats what I will do.

ChevyDave