Hi all, I know I probably could have searched this, but I need to step out very quickly, so don't flame me. I recently purchased a 87 se, and have taken off the cats. (stock exhaust).
I wanted to know which cats. (all three, just one/two, any?) could I hollow out, and still have enough back pressure to open my secondaries? The exhaust is stock diameter from the manifold right into the mufflers.
I am also considering replacing the muffler with a no-name apexi/HKS "fart cannon" type....will this still allow me to have enough back pressure to open the secondaries?
I know I can do one of the options to make the secondaries open, but wish NOT to at this point....any help is appreciated, thanks!!

 

It really depends on the car. Some people have seen the ports open with no cats to speak of. If your actuators are in good working order, it MIGHT work with no cats.

 

if you don't have enough back pressure take a knife and stab a hole in the tube from yor air pump and shove that line that went to the exhasut for the aux ports into the air pumpo and seal it with caulk or tape and then they will open with that instead

 

According to Aaron Cake, the third, final, main cat is all you need.

 

I used the pipe that connects directly to the manifold from a series five, because the one that was on my series 5 motor didn't have a cat. , and then went on to hollow out the second cat. and leave the main cat. in-tact.
Now all I've got to do is throw this thing back together, and probably add a set of cheap ebay "fart cannons" to complete my modded stock exhaust.
I know most of you are against the huge muffler look, but I'm not going to go all out 'till I go turbo.....
thanks for your help all!