Exhaust Manifold Flow Improvement?

[grubby65]

A few months ago I was reading in a magazine (I think it was Hemmings Muscle). In this article they talked about improving the flow through the exhaust manifold by running a type of abrasive liquid through it. If I remember right it was a '64 or '65 Plymouth that competed in the FAST series. I realize I'm being pretty vague, but does anyone know anyway to improve the flow through the exhaust manifolds. My car is a 1964 Dodge Polara with the 383, from reading on this website is a real bugger to put headers on.
Any thoughts would be appreciated.

 

[Kern Dog]

The "Extrude Honing" process is done to maximize the flow for those that are obligated to retain the factory exhaust manifolds. My understanding is that it is 3x the cost of a good set of headers while gaining about 3-4 HP.
Manifolds are for restoration purists and guys racing in FAST type classes.

 

[Johnny Mac]

It's called acid porting...it died with early class drag racing..and then the ricers dug it back up for their turbo manifolds. unless set on retaining manifolds, or trying to appear stock, i would imagine that headers would yield you much more gain in the long run. but anyways...here's some reading for you.

http://www.dsmtuners.com/threads/acid-porting-the-exhaust-manifold.445630/

they also did this on the powerblock a few months back on a flathead manifold.

 

[e-440]

I did this process to a set of factory set of hp manifolds from a company called EXTRUDE HONE, I believe they were on the east coast. They came out baby smooth. I would do it again as long as it is a stock or mildly built engine. The cost was about half again of a set of TTI coated headers. If you have lots of horsepower go with headers. that is my two cent.

 

[Longroof]

It's called acid porting...it died with early class drag racing..

Still quite a few NHRA Stock Eliminator cars have acid ported heads on them...

As far as headers the OP can get a set of headman's for pretty cheap that are a decent header... not as nice as a TTI but alot less money. As far as spending any money to increase the performance of the stock manifolds... spend it elsewhere.

By the way, really nice Dodge!!

 

[dvw]

Way more money than it's worth. The good manifolds are pretty decent. Beyond that buy headers, cheaper than extrude hone.
Doug