Punching out a HF cat

[caverman]

I picked these up used. One cat was already done this way. So I had to either buy another cat (for almost $200) or try this. It's not a good idea to run one cat empty and another one with the honey comb inside. It needs to be either one way or the other.

[IndeedSS1]

Originally Posted by caverman

I picked these up used. One cat was already done this way. So I had to either buy another cat (for almost $200) or try this. It's not a good idea to run one cat empty and another one with the honey comb inside. It needs to be either one way or the other.

You have to tell us if it stinks or not.

[caverman]

Originally Posted by IndeedSS1

You have to tell us if it stinks or not.

I haven't decided if I'm going to keep them or not. One way or the other I'll have some headers for sale soon.

[greenmachinedriver]

to anyone else who may read this, do not leave any catalist material at all in the cat. when it breaks up into dust it is extreemly abrasive, and belive it or not the exhaust pulses can push the material back into your engine. you can imagine the bad things that happen next. i know it seems counter-intuitive that it can move the wrong way inside the exhaust but it will, your exhaust valve does not close the instant your piston reaches top dead center on the exhaust stroke. it stays open for a short time as the piston starts its downward travel, couple that with another cylinder on the same bank starting to push out exhaust and you start to get backwards movement through the exhaust. i have seen this happen on bone stock cars that had a cracked or broken catalist, the carnage ranged from ruined piston rings to the engine ingesting its own valves. just somthing for you to think about before you leave those little pices in there.

[RANGERGOD]

Originally Posted by mikeSS

he did... there is no cats on his car. its also cheaper to do it this way.

Obviously he does...why not just run straight pipe from the LT if you are going to modify the cat?

[Bumblebee2012]

If you live in a state that requires emissions testing and a visual of all emissions devices, this is the common way around the law of the tree hugger land.

Here in the great state of Pa this is a common thing to do. You normally will also need to get a custom tune so that you don't throw codes because you can not have any OBDII trouble codes, otherwise you fail the emissions test.

Pain in the butt! But straight pipes are obvious criteria for failure, hammered cats are invisible to the technician and can get you your annual state sticker.

Sent from my Galaxy Nexus using Tapatalk

[caverman]

Originally Posted by greenmachinedriver

to anyone else who may read this, do not leave any catalist material at all in the cat. when it breaks up into dust it is extreemly abrasive, and belive it or not the exhaust pulses can push the material back into your engine. you can imagine the bad things that happen next. i know it seems counter-intuitive that it can move the wrong way inside the exhaust but it will, your exhaust valve does not close the instant your piston reaches top dead center on the exhaust stroke. it stays open for a short time as the piston starts its downward travel, couple that with another cylinder on the same bank starting to push out exhaust and you start to get backwards movement through the exhaust. i have seen this happen on bone stock cars that had a cracked or broken catalist, the carnage ranged from ruined piston rings to the engine ingesting its own valves. just somthing for you to think about before you leave those little pices in there.

I made sure that every bit of the material was out. Nothing at all in there and since it wasn't welded in or anything it all came out with a little persuasion.

Originally Posted by RANGERGOD

Obviously he does...why not just run straight pipe from the LT if you are going to modify the cat?

I posted the answer above but ultimately that would cost either $250 for a new set of HF cats or $120 for off-road connection pipes or this for free. Kind of the cheapest way out.