Milest

I am in the process of planning the overhaul of my L-48 for my 72 and have received some good ideas from this forum so far.

To avoid headers (I like the stock look) are there any modifications (porting, opening) that can be done to the stock exhaust manifolds?

I plan to do some head work, new cam, raise compression and don't want to choke it all off when it leaves the exhaust valves. I already have true duals (2 1/2") with an h-pipe, followed by Dynomax super turbos.

Appreciate your inputs, thanks.

KenSny

Articles have been written about smoothing out the runners and port matching the gasket. All recommend that you leave the step at the bottom of the port where it meets the gasket alone. Something to do with backpulse....

I doubt that it would make any difference as to "porting" them or not for a mild street applictation.

cardo0

Ya know I've seen some brand new ram manifold replacements that are 2&1/2" directly at the oulet. This was at the Pomona, CA swapmeet but a web search should find some. I don't know if they are opened up more inside but the stock rams are only 2" at outlet and then you need (I had) 2" to 2&1/2" connector pipes to use 2&1/2" exh system - added restriction.
Also a company called Brawsenski Racing used to specialize in porting these ram manifolds for class restricted racing.
Good luck and post your results. :chevy


[Modified by cardo0, 1:46 PM 3/4/2004]

markdtn

Stock C4 TPI cars have a mini-header with 2 1/2" outlets. That's what I have. C4 LT1 cars have a cast-iron manifold that has a 2 1/2" center dump outlet that is a nice swap into a C3 according to a friend of mine.

comp

:iagree: that is one of the Acid Porting Co.'s try to find or buy new the 2 1/2"
exit manifolds or your wastin time and money on most of the rest of the work,
the stock exhaust is a big HP/torque killer

Robert N

So is there any definitive answer on whether the C4 2 1/2 exit manifolds will fit the C3 block?

Milest

I just picked up a set of 2 1/2" ported Brzezinski manifolds off e-bay.

Hopefully they will clean up and all I will need are the studs and flanges. Where would be the best place to find those, I looked at a few vendors sights but did not find the 2 1/2" flanges.

Thanks

cardo0

Hey good catch! :thumbs: Were they straight from Brzezinski? Or from secound party? And if you don't mind, how many $. :D

Milest

I bought them from a second party, they said that they had surface rust and have only been used in three races. Won the bid at $102.50 + shipping. Should be here in a few days.
http://www.castheads.com is Brzezinski web sight, worth a look.