Cat removal
Thread Starter
Instructor
Joined: Aug 2014
Posts: 185
Likes: 0
Cat removal
On my 85 vette I have the original cat on there. I'm assuming it's clogged up and I was wondering on what type of performance increase that I would gain if I just took them off or cut them open... Thanks in advance!
Safety Car
Joined: Oct 2007
Posts: 4,426
Likes: 229
From: Pennsylvania
I don't have a cat on my 85. Antique plates so it's legal in my state. I have true duel outlets on each mufffler. In other words, both outlets on each muffler are open. It's not loud at all. But it does sound much better and deeper than stock. I would estimate another 10 hp without the cat and an additional 10 hp with true duel exhaust.
Last edited by FOURSPEEDVETTE; Oct 8, 2014 at 09:56 PM. Reason: typo
Instructor
Joined: Jun 2014
Posts: 133
Likes: 6
From: Minnesota
I haven't gotten around to messing with the cat on my '85 yet, but I can share what I know about the Monte SS (almost identical exhaust system).
it is a remarkably high flowing design, so if it's intact there won't be a big difference. 10-15hp is anout right, about like a/c con vs off.
If the case has any serious dings in it, the "tunnels" will be shifted and therefore blocked off and you could see a big improvement over what you currently have.
Rather than cutting it out, just remove it and bust the innards out. It'll have a nice muscular tone and will be easy to put back a good one if the need arises.
You only have to actually remove 2 bolts on each end, the others are slotted.
I had an '84 and '88 Monte SS and one good convertor that I would stick on just for inspection day.
it is a remarkably high flowing design, so if it's intact there won't be a big difference. 10-15hp is anout right, about like a/c con vs off.
If the case has any serious dings in it, the "tunnels" will be shifted and therefore blocked off and you could see a big improvement over what you currently have.
Rather than cutting it out, just remove it and bust the innards out. It'll have a nice muscular tone and will be easy to put back a good one if the need arises.
You only have to actually remove 2 bolts on each end, the others are slotted.
I had an '84 and '88 Monte SS and one good convertor that I would stick on just for inspection day.
Thread Starter
Instructor
Joined: Aug 2014
Posts: 185
Likes: 0
I haven't gotten around to messing with the cat on my '85 yet, but I can share what I know about the Monte SS (almost identical exhaust system).
it is a remarkably high flowing design, so if it's intact there won't be a big difference. 10-15hp is anout right, about like a/c con vs off.
If the case has any serious dings in it, the "tunnels" will be shifted and therefore blocked off and you could see a big improvement over what you currently have.
Rather than cutting it out, just remove it and bust the innards out. It'll have a nice muscular tone and will be easy to put back a good one if the need arises.
You only have to actually remove 2 bolts on each end, the others are slotted.
I had an '84 and '88 Monte SS and one good convertor that I would stick on just for inspection day.
it is a remarkably high flowing design, so if it's intact there won't be a big difference. 10-15hp is anout right, about like a/c con vs off.
If the case has any serious dings in it, the "tunnels" will be shifted and therefore blocked off and you could see a big improvement over what you currently have.
Rather than cutting it out, just remove it and bust the innards out. It'll have a nice muscular tone and will be easy to put back a good one if the need arises.
You only have to actually remove 2 bolts on each end, the others are slotted.
I had an '84 and '88 Monte SS and one good convertor that I would stick on just for inspection day.
Thread Starter
Instructor
Joined: Aug 2014
Posts: 185
Likes: 0
I haven't gotten around to messing with the cat on my '85 yet, but I can share what I know about the Monte SS (almost identical exhaust system).
it is a remarkably high flowing design, so if it's intact there won't be a big difference. 10-15hp is anout right, about like a/c con vs off.
If the case has any serious dings in it, the "tunnels" will be shifted and therefore blocked off and you could see a big improvement over what you currently have.
Rather than cutting it out, just remove it and bust the innards out. It'll have a nice muscular tone and will be easy to put back a good one if the need arises.
You only have to actually remove 2 bolts on each end, the others are slotted.
I had an '84 and '88 Monte SS and one good convertor that I would stick on just for inspection day.
it is a remarkably high flowing design, so if it's intact there won't be a big difference. 10-15hp is anout right, about like a/c con vs off.
If the case has any serious dings in it, the "tunnels" will be shifted and therefore blocked off and you could see a big improvement over what you currently have.
Rather than cutting it out, just remove it and bust the innards out. It'll have a nice muscular tone and will be easy to put back a good one if the need arises.
You only have to actually remove 2 bolts on each end, the others are slotted.
I had an '84 and '88 Monte SS and one good convertor that I would stick on just for inspection day.
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Race Director
Joined: Oct 2005
Posts: 11,768
Likes: 175
From: Rolla Missouri
2021 C4 of the Year - Unmodified Finalist
St. Jude Donor '10 thru '25
There are Federal laws about tampering with any factory emissions equipment.
Now with that said, the chances of you being caught or fined for it are slim.
But a muffler shop could get in real deep trouble doing stuff like that.
Racer
Joined: Apr 2010
Posts: 372
Likes: 23
From: Harper Woods MI
This is the exhaust I installed on my '84. There are some fitment issues that needed to be handled by a local exhaust shop. But they do sound great once everything is set.
http://www.parts123.com/parts123/yb....5Z50000050F~~~
http://www.parts123.com/parts123/yb....5Z50000050F~~~
Burning Brakes
Joined: Apr 2009
Posts: 1,228
Likes: 10
From: That one city...you know that one. Idaho
Just because they don't do emissions testing in your state, does not make it "legal" to remove your catalytic converter.
There are Federal laws about tampering with any factory emissions equipment.
Now with that said, the chances of you being caught or fined for it are slim.
But a muffler shop could get in real deep trouble doing stuff like that.
There are Federal laws about tampering with any factory emissions equipment.
Now with that said, the chances of you being caught or fined for it are slim.
But a muffler shop could get in real deep trouble doing stuff like that.
You normally don't see cars getting fined for exhaust noise unless it is over the db limit in that area.
Team Owner
Joined: Sep 2003
Posts: 20,172
Likes: 672
From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
A gutted cat will only make the exhaust stink.
I found a good Magnaflow and the SOTP power didn't change.
The NOS sticker is always worth 15hp....
Safety Car
Joined: Oct 2007
Posts: 4,426
Likes: 229
From: Pennsylvania
Just because they don't do emissions testing in your state, does not make it "legal" to remove your catalytic converter.
There are Federal laws about tampering with any factory emissions equipment.
Now with that said, the chances of you being caught or fined for it are slim.
But a muffler shop could get in real deep trouble doing stuff like that.
There are Federal laws about tampering with any factory emissions equipment.
Now with that said, the chances of you being caught or fined for it are slim.
But a muffler shop could get in real deep trouble doing stuff like that.
OK, bad choice of wording. It's not what I meant. I don't have to get emissions tests done on a car with antique plates is what I meant. They're exempt in my state. I'm fairly sure everyone is familiar with the "federal Laws".
Last edited by FOURSPEEDVETTE; Oct 9, 2014 at 08:57 PM.
Instructor
Joined: Jun 2014
Posts: 133
Likes: 6
From: Minnesota
It takes roughly 10 hp to drive the A/C compressor when it is active.
When it's disengaged, it uses almost nothing. Also, I believe these cars disengage the A/C under heavy throttle.
I guess it's a bad frame of reference in these days of cputer controlled throttle, but on a carb'd car there is slight bog when the compressor engages. Almost unnoticable. That's what 10hp feels like.
Team Owner
Joined: Jul 2004
Posts: 28,366
Likes: 3,257
From: Hartford WI
I guess I should rephrase that...
It takes roughly 10 hp to drive the A/C compressor when it is active.
When it's disengaged, it uses almost nothing. Also, I believe these cars disengage the A/C under heavy throttle.
I guess it's a bad frame of reference in these days of cputer controlled throttle, but on a carb'd car there is slight bog when the compressor engages. Almost unnoticable. That's what 10hp feels like.
It takes roughly 10 hp to drive the A/C compressor when it is active.
When it's disengaged, it uses almost nothing. Also, I believe these cars disengage the A/C under heavy throttle.
I guess it's a bad frame of reference in these days of cputer controlled throttle, but on a carb'd car there is slight bog when the compressor engages. Almost unnoticable. That's what 10hp feels like.