91yellowfellow

Well like the title says I replaced my Front Y with one with out precats in it. I dont know if its just the extra noise or not but it does feel like she has a little extra pep in her step. Not a 50hp gain or anything crazy like some of them air foils and K&N air filters offer but it does feel like I picked up a handfull anyway. Anyone else remove theirs and notice a diffrence or is it all in my head.

ch@0s

I does help, not as much as an airfoil.
Your SOTP meter is working correctly.

ggrassmid

I gutted my cat on my '85. Before stock tires 255 could go from stop/brake to WOT and spin tires. Gutted cat and now can spin 315's without thinking twice. Made a big difference in how my car ran and reacted

eaglevision993

My pre-cats are also gutted. I did this when one broke into pieces and rattled.
I plan to install a new front Y pipe when I do the exhaust system this summer. The hollow cat chambers might cause resonances.

The car feels stronger without them, I felt that too. Noise level increases of course.

harrisr

noticed a better response and of course more noise right away.

redvetttes

Did you guys pick lots of drone
somebody said to cut the pre cats off and weld straight pieces of pipe on
Want to do that 1st thing when spring gets here
Just like to know what I will be getting into with the extra noise

CREWZIN

I have the "Y" without the pre-cats, a gutted main CAT and the air foil. Goes like a scalded cat. No pun intended.

Sweeride39

Does anyone produce a front Y pipe without the cats that mount to the stock headers?

CREWZIN

Got mine from either Mid America or Ecklers and my headers are stock.

coupeguy2001

I bought an 85 front Y pipe out of a wrecking yard. It doesn't have precats. I could barely keep up with traffic on a major hill here in Phoenix, and when i got rid of the precats, wow, what a difference. I also ported the exhaust manifold flanges, and I really noticed some oomph when I did those two things. If you port the exhaust manifolds, grind away the material that chokes down the pipe weld at the flange, but don't get rid of all the discoloration on the flange. It will flow better, and be strong enough not to crack.

ch@0s

There is a lot of material there also gring the air tubes flush. On my 86 i cut the y right behind the cats gutted them then had it welded back together.

prinzSD455

CREWZIN, who drew up your avatar? I am looking for someone to do a couple of carictures of my 3 cars.

coupeguy2001

Wel, I also did grind the air tubes flush. I bought small bullet cats to replace the precats and welded in a "test" tube instead of the main cat.
This is going on soon.
I am going to ditch my true dual setup soon. One of the bricks in the cats broke and part of it is banging around inside the muffler. Such an annoyance. The cats are too far back from the engine to lightoff properly so I will get the other setup installed.
The other thing wrong with it is the pipe welded right ahead of the cats isn't stainless, and the inside of the pipe is flaking off a little bit of metal. The flakes bunch up and choke off the cats then the next time i start it up, it runs fine, every start is different, and depends on where the flakes lay.

TIMSTERS VETTE

Please pardon my ignorance, I am just a shade tree mechanic. But when I hear gut the cat convertors, is it an easy thing to do?

pmihaltian

You can get a cat-less front Y-pipe at most of the Corvette Parts houses. Here is one with a high output main cat:

http://www.ecklers.com/corvette-y-pi...1986-1991.html

ggrassmid

I busted mine out with a piece of metal rebar I had laying around

8valve

WHen you replace the front Y pipe with one without Pre Cats, and also remove the Main Cat, will you have any problems with the Oxygen sensor operating correctly ? I am also considering running duals all the way back. Somewhere I think I read on the forum that removing the cats woudl cause Oxygen sensor problems. I have a 87 with only one Oxygen Sensor on the left pipe.

Thanks
8Valve

Casket86

ch@0s

No it won't.

GREGGPENN

www.allencorvetteexhaustsystems.com

They are the only one I know of that makes a 2.5" front "Y" w/o cats. Not sure if the OP went 2.25 or 2.5. Either one would help.