I have an 88 automatic that is mostly stock except for shift kit and open air lid. I am putting hedman full length headers , Y - pipe and magnaflow stainless exhaust on. My few questions are 1) how much power increase can I expect and will it be a sotp difference? 2)will removing the cats completely cause my car to trigger a check engine code at all? hoping it wont be too loud and be lots of fumes. Also will the mufflers provide enough backpressure without cats?

 

First, why the Y-pipe? Are you going to keep the main cat for emissions requirements (you didn't say where you live).

I have true duals on my '87 with Hedman Elites. That did make some difference but the car already has a mild cam (ZZ4), bored .030 over, balanced, and intake runner port matching. I figure it was worth a good 15 HP.

You will need to install a bung for the O2 sensor. I cut a hole in the left side collector flange and welded the bung in. I used the existing O2 sensor and the sensor wire harness was long enough to connect it up. With the sensor that far away, it will take a bit longer for the ECM to go into closed loop but there won't be any error codes set with headers.

I wound up replacing the OEM large Delco starter with an Hitachi style mini-starter that I bought from Summit Racing. It would have been a royal PITA to get that old large starter back in place after putting the passenger side header in. And if the old starter would have failed, the passenger header would have to come off. The mini-starter will easily go in and out with the header in place. The Summit starter didn't require any wiring changes; a simple plug-n-play.

You will have to make a bracket for the lower rear alternator mount. Do a search on something like "header install"; there are a few threads with pics that show what needs to be done. You my have to fab a snall bracket for the oil dipstick tube. It has to come out for the passenger side header install.

The passenger side header tubes will be close to the gas lines so get some insulation to cover the feed and return lines. Also insulate the wiring harnesses near the starter.

 

I live in New England , it's registered as an antique so emissions are not an issue , so I figured no cats=more power?? Also I was told putting a full exhaust long tubed to mufflers brings at least 25 - 35 hp and triggers no codes.

 

If the o2 is in front of the cats like on a c4 your good, delete them and if it's behind the cat you gotta keep em(get some hi-flows) is they way I've been told. I've also always herd you should upgrade to the heated o2 sensor with longtubes. The longtubes will help SOP and it depends on the condition of your cats and mufflers as to how much they help.

This spring I deleted my pre-cats and cat but mine weren't plugged up so I don't expect too much gain from that. I also put on a hi-flow race muffler and several other small things, but still haven't fired it up and prob won't be anytime soon as I have been working on my c3 more.

 

I replaced the factory mufflers with magnaflows and the cat is from 1988 so I'm sure it will make a difference. Ive been told the codes wont trigger but I wanted to check wit this forum to see for sure. I want it to be loud but not obnoxious , I think with a 9.5/1 compression it shouldn't be.

 

My stock rear y to the stock mufflers broke last year. Right after the hanger so I just took them off and had a bit of straight pipe after the main cat. My c3 with full single 3" no cat and a magnaflow xl chamber muffler was still louder, so I do know the cats sound deaden good.

 

If you're going longtubes, I'd suggest removing your cats.

Why? My anecdotal evidence is my car almost catching on fire....twice...trying to keep them!

You have a car that is even older than mine.

You don't need them.

 

A good quality cat will not degrade performance these days.
And they do help to clean up the air somewhat.

 

Removal of Cats on a stock engine is an iffy situation.

If the tune is not adjusted, at WOT you'll have a slightly richer mixture and have to deal with the computer errors.

Power increase (assuming all is normal) will be a small increase because of the lowered backpressure. (most likely but not always true)

If its a street car that you use often you might consider having cats and no mufflers.