whould a 3in cat back be enought to let my Big block breath easly... the place in my town wants 700$ to do true dual from headers back... i was thinking buy the cat back... a cut out on each side... cat back choices are

Hooker
Flowmaster
Edlebrock
Borla= to much money

 

What kind of big block? A mid 90's 454 barely making 230hp is going to have different breathing characteristics than a built 427. Does this engine have any sort of power adder? Does it have ported or aftermarket heads and a long duration cam? If so, I would recommend dual 2.5in. If you want to run a single pipe, consider a 3.5in or 4in the absolute minimum.

 

i cant find any where that sells 4in exhaust.....The motor is pretty wild its pushen around 650hp if not more

 

How about here.

 

for the 630$ 4in i might as well go to the guy in my town and pay 700 for the true duals

 

Yeah, you can also pay for the ground clearence issues that accure with dual systems.
Any exhaust shop should be able to make a dual exhaust for our cars for cheaper than 700 bucks, that is unless they are routing it with no compromise to ground clearence.

 

i still need a custom y pipe made

 

You dont need a ypipe for dual exhaust. To properly set it up, however, you do need an h pipe.

 

If you make all the bends required for the no compromise option, I wonder how they will be able to do it with mandrel bending for that price. If it is not mandrel bent, it will have all kinds of crimps in the pipe.