1987C4

I want to get some opinions from the group on an idea I had. I have a 1987 coupe with the typical pre-cats that I'd like to eliminate. I have seen the front Y-pipe that is already premade and ready to bolt up to the exhaust manifolds and goes to the main cat. I believe Dyomax makes that one.

Here's my question. Would it be possible to just cut the pre-cats out and put in a straight section of pipe in it's place? I was thinking I could easily save some money by using my reciprocating saw and carefully cutting the precats out and using some unions and straight pipe with some good quality band clamps, it would be a cheap and easy modification. Is there any way this could hurt the O2 sensor? I may remove it while I do the work anyway. Is there any performance gain from something like this?

In this same vein, does anyone know off the top of their head the size of these pipes? I have some brand new 2 1/2 inch pipe left over from a Firebird exhaust modification I did recently, so if it's 2 1/2 inch, I'm almost set! Sorry for the dumb question, just too lazy right now to crawl under there!

Thanks for an insights. I just can't imagine it would be a problem. Anyone know how much more noise it will create if I eliminate them? Thanks!

Brad

VAHROOM

I had a local muffler shop remove my precats. I had a short piece of pipe welded in where the cat used to be. I also had them remove the mufflers and make eliminators with stock looking chrome tips. The whole thing cost me $120. $40 for the cat elims and $80 for the mufflrer elims. They were done in less than an hour and did a professional looking job.

skateparkdave

I did it in hopes of some gains but honestly I just didn't feel much. Maybe a little, but not much. At the time I also did a cat back with monza mufflers so I did get a nice rumble.

I have since gone with long tube Hooker headers and there's the difference I was looking for.

If you do it you should just take it to a reputable muffler shop and get them to just cut out the pre cats with a torch and weld in some tapered sections. They can, or should, be able to do it for around $35. Band clamps and all that just seems like an exhaust leak waiting to happen if you ask me. JMHO

Aardwolf

Well if you can learn anything from what I did.. I used a combo of a cutting wheel (it must be large enough dia to cut around a 2.5" pipe without the shaft of the wheel causing the cut to be to shallow) and Sawzall to remove mine. It was not hard nor long work, but you must have good tools and decent elevation of the car. I did nothing with the O2 except make sure the wire was protected. You'll cut the pre-cat off about 4-5" from the O2. I started the car up with just those down pipes. One because she sounded fricken awesome and is not a muffler virgin anymore! And two, to blow out any metal bits. Ya gotta start her up just once!
Then I had a local guy weld in some pipe. I thought he charged kind of high. I have some mandrel bent tube but I do not have a welder, YET. So I went with the welding. The car sounds MUCH better at WOT and has more power. SOTP! At low RPM the sound is deeper but not really louder. In some ways I swear the car is quieter, but at the same time the sound of rumbling behind is slightly more noticeable.
I spent about half what the Y pipe sales for but spent my time.

1987C4

Thanks for the replies. I may just try this as I can do it for little cost. Not much lost if it is not a great improvement. The band clamp idea is one that I would not normally consider, but after modifying the exhaust on my Firebird this past week, I'm sold on them. Great seal and very heavy duty pieces. I may just take it to the shop anyway, but since I can do this for so little, I may try it anyway. I'm concerned about the increased sound, but it doesn't appear to be much louder than stock from what you say. Thanks for the observations. Anyone else care to weigh in on this?
Brad

IBEAM700

Can i have your old pre-cats?

AGENT 86

I did my cat removal myself but brought it in for the pre cat elimination. Plasma cutter made quick work of removing them. They then formed and flared 2 pieces of pipe and mig welded them in. In and out in less than 30 min.
Some things are best left to the pros with the right tools.

1986Z51

I bought a main cat (Catco) and Y-pipe combo on Fleabay last year. The pipe was stainless and decent quality but the fit was crappy. The flanges at the exhaust manifolds leaked and there wasn't enough clearance at the rear Y to remove the 4+3 O.D. pan for changing ATF. I decided to replace my original pipe after gutting the cats -- pried off the heat shields, smacked cats all around with a rubber mallet, then bent and drove a 3/8" rod into the cats through the flanges (alternated with a 1" or so wire bundle, the kind used for wiring up an electric stove, stiff yet flexible). The last thing that came out from each cat were a couple of oval wire braids and I knew I was done. It took a couple of hours. Thought about cutting and welding pipe sections but that wouldn't have been a DIY job for me. Car has more rumble now (Borlas) just as others described above. A bonus is a lot less heat radiated through the floorboards, also less heat cooking the clutch hydraulics and underhood wires.

Runum

I bought some 2 1/2" mandrel bent U bent pipe from Summit and welded up my own complete mandrel bent front Y for about $100. Did a lot of other mods at the same time. Can't tell if the Y pipe alone was worth it. From what I understand I really need to go with headers though. Maybe in a year or two, when I get enough energy built up.