need cat and exhaust advice on 87

[87blackroxi]

I just spent 1 1/2 hours reading past posts and am totally confused on the matter of removing cats vs replacing with high flow. and straight pipes vs magnaflow/flowmasters. i have an 87 with 130k. completely stock.
I am considering removing the stock cat and going with magnaflows or straight pipes. i've read contradictory info. gain hp/lose torque. need help.
what would be the best set up? i would like it to breath way better than it does. growling noises a bonus and max hp without losing much torque. what do y'all think?
` thanks in advance.
shane

ps I live in florida so no emmissions!

 

[c4cruiser]

Firts, what are the FL emission laws reagrding emissions testing? Do you have to pass some sort of smog check? Federal law prohibits a shop from removing cats or replacing a cat in good working condition with another. Of course if you do it yourself, it may not be an issue unless you have to pass some sort of smog test.

The older GM cats don't flow as good as the later C4 cats do and the early C4's still rally had a single exhaust system. The exhaust pipes with the pre-cats joined at a "Y" and flowed into the main cat. A single pipe from there went to another "Y" pipe and out to individual mufflers.

The easiest mod to do for a great sound and pick up some power is to simply have a shop remove the mufflers and just installstraight pipes in their place. This shouldn't cost more than $50-75 to do and should even include some chrome tips at that price.

The O2 sensor still needs to be connected to the ECM so if you remove the cats, you will most likely need a heated 02 sensor to keep the SES light from coming on.

If the engine is completely stock, opening up the exhaust too much may result in the loss of some low-end torque. HP may go up slightly at the top end, but the TPI intake runners are the biggest limiting factor. The runners effectively limit power at the top end but the TPI motor is really best at lower RPM ranges. The torque peak with the TPI motors is down low in the RPM range.

You can free up some HP with some free-flowing mufflers (elims or no mufflers at all and keep the cats. If you dump the cats, don't go overboard on pipe sizes. Stay at 2 1/2" or 2 3/4". A 3" system will rob some power as it reduces backpressure to the point where power falls off with an othewise stock motor. A set of long tube headers will help but I would recommend a mild cam and some good head work (port matching the intake runners, a good valve job) and the typcial balance and blue print of the rotating components.

 

[fast.asleep]

whatever you decide keep the old parts just in case you end up with emission laws in the future.

that being said, drop the entire exhaust system.

On my '87 I went with a set of Headman headers, dual 2.5" pipes and Hooker performance mufflers (no cats). Huge power increase, got all new parts, and the whole setup cost me less than a set of TPIS headers.

 

[AdvancedAutoCC]

I just spent 1 1/2 hours reading past posts and am totally confused on the matter of removing cats vs replacing with high flow. and straight pipes vs magnaflow/flowmasters. i have an 87 with 130k. completely stock.
I am considering removing the stock cat and going with magnaflows or straight pipes. i've read contradictory info. gain hp/lose torque. need help.
what would be the best set up? i would like it to breath way better than it does. growling noises a bonus and max hp without losing much torque. what do y'all think?
` thanks in advance.
shane

ps I live in florida so no emmissions!

Your best course of action is to have straight pipes bent up from the manifolds back, using a Tru-X crossover in place of the stock cat. You can use your choice of mufflers going this route (Magnaflows are quieter than Flowmasters), and if you're concerned about being emission legal, you can have some high-flow cats placed inline. No exhaust shop is going to do away with the cats, but if you ask them to make you an "off-road" exhaust that you'll bolt up in place, they'll most likely do that. Make sure you have the O2 bung located as close to the manifold as possible (not necessary with longtube headers that already have one), and you'll have no trouble with the "SES" light tripping an O2 code. Longtubes, you may need to go to a heated sensor, manifolds retain enough heat not to need it.
As to "max hp" stuff, your best bet is mandrel bent tubing, but it comes at a price. Most exhaust shops use a crush bender (I do as well) for most custom bent stuff, which is good enough, but mandrel bends are much smoother through the radius of the bend. Plus, when you crush bend, the overall diameter of the pipe is reduced through the radius, as opposed to mandrel bending which maintains the same diameter. The reason most shops do not have mandrel banders is due to the extremely high cost ($30,000 and up, plus consumables). Some shops (mine included) fabricate mandrel bent systems from scratch, but the cost is not cheap (but....you get what you pay for). See Hib's article about the exhaust on his ZR1 for information about this type of system. Good luck in whatever you decide to do.

 

[Edmond]

On my '87 I went with a set of Headman headers, dual 2.5" pipes and Hooker performance mufflers (no cats). Huge power increase, got all new parts, and the whole setup cost me less than a set of TPIS headers.

That's what I would do. Probably cost you less than $700. It will have some serious growl.

 

[fast.asleep]

That's what I would do. Probably cost you less than $700. It will have some serious growl.

I don't know how much hp I gained but seat of the pants feel is improved

Once you start though it doesn't end. Now I'm trying to decide what I should do on the intake side. With an automatic tranny I'm leaning towards the Edelbrock intake manifold and runners. - but the LT1 intake looks interesting as well. After hearing rrubel's horror stories with the Superram, I'm not going near it. I remember Mick picked up an LT1 intake but didn't install it.

I'm stuck

 

[87blackroxi]

thanks everyone

fastasleep,
where did you get all your gear and did you put it all on or did a shop?
also is $700 about right? and lastly what company did you get it all from and do they have a website?

what kind of sound does it all produce with the hooker performance mufflers?

in florida we have no emmissions at all. but very good idea to keep the parts. never know with legislature.

 

[87blackroxi]

o2 sensor

That was the other thing I read alot about that i'm still hazy. I believe on my 87 I only have one sensor before the cat. will i still need the o2 sim or ecen a heated one if i remove the cat?

 

[fast.asleep]

fastasleep,
where did you get all your gear? and did you put it all on or did a shop?
also is $700 about right? and lastly what company did you get it all from? oh , and do they have a website.
thanks

I live in Canada so availability is much better where you are.

I picked up the headers and mufflers from a local speed shop

Headers:
http://www.hedman.com/pages/hedmanmain.html

Mufflers:
http://www.holley.com/HiOctn/ProdLine/Products/ES/ESHHM/Aero.html

Everything was installed at a friends shop. He made the pipes for me but if I was in the states I would have gone with Mid America's "offroad" exhaust:
http://www.madvet.com/shop?frame=3.36.928

It would have bumped me just over $700 US but for $300 I'd have pipes that would last forever.

One word of advice, if you do go with Headman, don't buy the coated headers. I was told the coating is thin and cheap. Have the coating done by a reputable coating shop near you. It might cost a little extra but it's worth it.

 

[fast.asleep]

That was the other thing I read alot about that i'm still hazy. I believe on my 87 I only have one sensor before the cat. will i still need the o2 sim or ecen a heated one if i remove the cat?

yup, one sensor before the cat

We drilled a hole and welded a bung to the pipe and haven't had problems with the sensor yet. (do this and dry fit the headers before you coat them)

 

[87blackroxi]

ordering

did you get everything from a shop and they did the work? or did you order the parts and bring them in to the shop?

 

[fast.asleep]

did you get everything from a shop and they did the work? or did you order the parts and bring them in to the shop?

I ordered the parts from a local speed shop (who didn't do installs) and took them to a friends shop but that was just my situation. Once you have the parts picked out call around.

 

[Edmond]

I think Hooker headers come with an O2 bung already on them.

I read that a lot of guys also like Arizona Speed and Marine's large tube runners. Don't quote me, but they might be siamesed. I would definitely go with the Edelbrock intake. I was told by more than one person that the Edelbrock and the TPIS Big Mouth are identical down to the casting numbers on the intake. I was also told that TPIS doesn't really make anything, they just restamp their name on there and sell it for more.

 

[ZumZum]

yup, one sensor before the cat

We drilled a hole and welded a bung to the pipe and haven't had problems with the sensor yet. (do this and dry fit the headers before you coat them)

If I can chime in and ask a question. I'm looking at the dual exhaust system offered by Corvette Central

http://www.parts123.com/PartFrame.asp?ZTM=cadefibf&GHOME=www.corvettecentral.com&TITLE=Corvette_Central

Do I have two O2 sensors, one in front of each precat? Or just one in front of the main cat? It appears these pipes come with 2 sensor ports. If after the installation of the exhaust system the sensors "trip a code" isn't it possible to have a custom chip burned that would eliminate the problem? After I do my mild mods (not changing the motor internals with the exception of 1.5 rocker arms) I am thinking about replacing the chip. Thanks for letting me cut in.

 

[Edmond]

Zum,

You have one O2 sensor. If I recall correctly, it's on the driver side exhaust manifold right before the "pup" cat.

I don't know if a chip can be burned to eliminate the SES. But they sell O2 simulators that will trick the CPU into believing there is an O2 sensor there.

 

[ZumZum]

Zum,

You have one O2 sensor. If I recall correctly, it's on the driver side exhaust manifold right before the "pup" cat.

I don't know if a chip can be burned to eliminate the SES. But they sell O2 simulators that will trick the CPU into believing there is an O2 sensor there.

Edmond,
Thanks for the quick reply.

 

[WhalePirot]

will i still need the o2 sim or ecen a heated one if i remove the cat?

It is more than a PITA by flashing the SES. It feeds back to the ECM so it can best adjust the fuel mixture, etc. and get the most from your engine. Why would you not run it? The ECM can be a troubleshooting aid, if you learn about it.

When I started my first mods, with the stock engine, I felt no performance gain with a test pipe in place of the CAT; with long tubes and Flowmasters, plus a mild cam.

 

[Mad-Mic]

If I can chime in and ask a question. I'm looking at the dual exhaust system offered by Corvette Central

http://www.parts123.com/PartFrame.asp?ZTM=cadefibf&GHOME=www.corvettecentral.com&TITLE=Corvette_Central

Do I have two O2 sensors, one in front of each precat? Or just one in front of the main cat? It appears these pipes come with 2 sensor ports. If after the installation of the exhaust system the sensors "trip a code" isn't it possible to have a custom chip burned that would eliminate the problem? After I do my mild mods (not changing the motor internals with the exception of 1.5 rocker arms) I am thinking about replacing the chip. Thanks for letting me cut in.

it shouldn't trip the ses light for doing exhaust work at all.

here is a link to a short vid of mine after long tube headers install with gutted cat and dumps (no mufflers) sorry the vid quality isn't the best being choppy had to reformat and never redid the vid.

http://www.corvettekillstories.com/videos/members/Mad-Mic/TPiS_Long_Tube_Headers_Open_Exhaust.wmv

turn it up! sorry bout the F bomb at the end

BTW i am installing the heads cam and LT1 intake in a few weeks

 

[fast.asleep]

BTW i am installing the heads cam and LT1 intake in a few weeks

let us know how it goes. I'm sure there are a bunch of us who are curious

 

[87blackroxi]

dual exhaust set up

If I can chime in and ask a question. I'm looking at the dual exhaust system offered by Corvette Central

http://www.parts123.com/PartFrame.asp?ZTM=cadefibf&GHOME=www.corvettecentral.com&TITLE=Corvette_Central


what does anyone think of these? it looks like the set up i am looking for?
shane