Racod

I am considering long tube headers and exhaust on my l98. It is registered as a classic car and will not need emissions tested.

My question is are there any negative effects of removing the cats? Smell? Rideability? Durability?

Thx

LD85

stock or modified engine?

Racod

Stock. I was going to add magna flow pipes too. What could be a good set up? From what I read TPIS seems to have the best product for the c4s.

LD85

You'll be fine with no cats, i took mine off way back and if you have a decent cat back, you'll get some seat of the pants improvement too

Magnaflows are good, i had them for a while but now i have Pypes true dual's and I love them

Magnaflow

Racod

Do you have headers???

65Z01

How about the "drone"; any change from cat-back to duals??

I had Magnaflow cat-back with OEM headers, hi-flow Y & cat and, though it sounded "mean" at WOT, the drone was a bit much...

LD85

Yes I have headers, 1 3/4"

I did not have drone with Pypes true dual.

Magnaflow Y system had a slight throne in a specific narrow RPM on the interstate

Keystring

I hate cats.

I'm more of a dog man myself..

shakedown067

With no cats you lose low end torque, but gain upper RPM horsepower. Personally, I say leave them be unless it's a track car.

GREGGPENN

I've never heard of no cats killing power -- anywhere. But, I agree that keeping them (unless you're tracking it) is the better option.

I don't remember anyone without cats not complaining about smell (even eye-burning). LD85: Didn't you complain about that too?

shakedown067

I actually JUST saw before and after dyno results. I believe on a LS-1 Corvette. I'll have to try to hunt down that article. Was on facebook, so I'll probably never find it again.

vader86

Removing cats won't change the torque on an L98 motor, the stockers are very restrictive.

I initially had more drone with a straight pipe instead of the main cat with the TPIS headers. Going to true duals helped some of the drone, but its strongly dependent on the muffler you are using. My 88 has the same exhaust as the 86 - TPIS into duals- but the mufflers made a big difference.

Racod

Has anyone keept the stock manifolds and just replaced the pre-cats with a free-flow Y pipe?

shakedown067

Ah, didn't think about that.

Racod

just a little tight on cash. If I can remove the precats and install a magna flow exhaust with the secondary cat in the Y it will be a lot less. The only stock part would be the exhaust manifold.

magna flow $599

c4cruiser

My '87 is primarily an autocross and track day car. I removed all of the original exhaust and went with true duals, an X-pipe, and DynoMax Ultra Flo mufflers. I stayed with the stock 2-1/4" pipe.

One caution with removing the stock exhaust (classic car plates or not) is that mufflers shops may not want to do the work. Removing a working cat from a car could result in a 5-figure fine from the EPA if they get caught. What you can do is to remove the plates, remove the exhaust yourself, then trailer the car to a muffler shop and tell them you are building an "off-road" car that won't see street use.

The Dynomax mufflers are very quiet at city and highway cruise speeds. At WOT they are loud. But there is very little interior resonance at cruise which I found surprising as all of the carpeting/padding has been removed. Members that have installed Flowmasters reported lots of resonance especially with the 40 or 44 series.

Racod

it will will have the main cat. Just taking out the pre-cats

LD85

Pypes true duals are @ that cost

http://www.pypesexhaust.com/sys-vette2.html

mixalive

For the folks whose cars are not registered as classic cars: In Texas, cats are not required on vehicles 25 years or older. Even if factory equiped. Check with the DMV in your state.

GREGGPENN

What's reality and what's law can be two different things. Internet search of Texas converter law seems to indicate the need to maintain existing factory converters. It's also been repeatedly posted that EPA regulations outweigh state law in this area.

But, local inspection is the bottom-line and what you have to answer for.

I would also add that your eyes and nose will have to answer too!