ride250s

I know it is hard to come by a complete dual exhaust system for 84-91 vettes... and after reading some other posts today I concluded that the Melrose exhaust with long tube headers and 3 inch exhaust might be too much for my all stock motor. So that leaves me with no choice really other than to go custom. I should add that I also want to run CATS, so this cancels the option of buying MAMS dual system.

So i have been looking at what I can buy from different companies to get what I want. This is what I have foud so far, and I would just like some input on to whether these items will be good for an all stock 1987 Corvette.

Headers: Hooker 2149HKR (They include all the emissions ports, and are mid length, or should I be going with a full length on a stock motor??)

CATS: (What are the best high flow cats? Are pre-cats the same as other cats just closer to the headers?)

Mufflers: Corsa (I just love the sound... and they are 2.5in)

Tubing: 2.5in custom bent at a local shop and will have the 2.25in cats added slightly behind the headers. (Will I need O2 sensor bungs installed also?)

X-Pipe Crossover: Magnaflow 2.5in diameter x 12in long installed in the middle where the old single tube used to be.


Does this all sound good?

Again my main questions are:

Should I be running Full lengh headers? What CATS should I uses? What is the difference with pre-cats? Will I need O2 sensor bungs?

REMEMBER, ALL STOCK MOTOR!!!

daytonaer

You don't want this because you cant run cats? http://www.mamotorworks.com/corvette...ywords=603-490

I'm not sure you understand, that you could just cut a section of pipe out the size of the cats to install them. Really no different than having a muffler shop bend it custom would likely do.

If you want headers and can afford and are allowed them legally, might as well install full length headers. You already have shorty headers of sorts.

Catalytic converters, all that matters is they are 3 way converters, could get with a bung if you want to retain the air injection system. Pre-cats and main cats are simply older technology which are all combined into newer 3 way converters.

If the headers do not have O2 bungs, you will need to add one to the drivers side exhaust, the collector is a good place. Or you could add just after the collector. Ideally you want the sensor relatively close to the head, if its too far away, you could add a self heated O2 sensor.

x pipe may get crowded behind the cats, depending what size the ones you get, but it has been done (LT headers, dual cats, x pipe)

If your running 2.5 pipe, might as well run 2.5 converters.

Re-cap, Full length headers if you can swing it, Whatever cats you want; 3 way you will need no pre-cat and having provision for air injection helps if you have air injection. You will need one O2 bung on drivers side pipe, but may already exist on some headers.

Cyclonite

Why 2-1/4 cats if you are running 2-1/2 pipe the rest of the way? Won't that just create extra restriction in the flow, which is what you are trying to eliminate with a performance system,right?

daytonaer

Just thinking, If your running Long tube headers, dual cats and an x pipe, shouldn't really worry about buying a kit as most of it would be cut out and thrown away for all those components. But it would mean less time at the bender.

ride250s

Exactly, if I wasn't going to use headers I would consider the kit. Also when I was looking at cats all i could find was 2.25... well now I have found some nice Magnaflow ones that are 2.5 and also 3-way!

Thanks for the input

ride250s

The biggest concern I had with the longtube headers was a loss of power, because my motor is all stock and I thought mid length headers would aleviate that potential problem?

c4cruiser

Long tube headers may not give you a lot of room for installing cats. Most of the oval/roumd cats run 9-12" long and need some space between the cat and the body. Attached are some pics that were floating around the Forum last year showing headers installed in an C4 with a 4+3 tranny. IIRC, they are Hedman Elites with a 2.25 Y-pipe.

As mentioned, you will need one bung installed in a header for an O2 sensor. The chances are that it will need to be a heated O2 sensor so that it can fool the PCM into going into closed loop. Typically, an O2 sensor would be installed into the collector but some have just had a bing welded into one of the tubes on the left side.

I just finished dumping the front Y-pipe, the cats, and the rear Y-pipe for a true dual exhaust system on my 87. The car doesn't see a lot of street use as it is primarily my aoutcross and track day car. This exhaust configuration will obviously pass any sort of emissions test but I'm not required to pass one to get license tabs.

Also with long tubes, you will really want to go to a small gear-reduction starter. The OEM starter has to be removed to install the right side header (along with the oil dipstick tube). When the header is set into place and a couple bolts are started, you re-install the starter. Once the header is fully bolted up, the OEM starter will not come out unless you pull the header

The dipstick tube can be a PITA to remove and it may even break off in the attempt.

There are LT headers that have connections for the AIR system (Hedman has both AIR and non-AIR styles). But if you remove the AIR tubes, you might want to get an AIR pump eliminator kit to clean up the front of the motor. You can do this even without headers too.

You can stay with 2 1/4" pipe or go to 2.5" . On a completely stock motor, you may not see much of a difference. With headers and maybe some later mods like a cam, head work, or more cubes, the 2.5" is the way to go.

Definitely get a good X-pipe to help with noise and especially interior resonance. The car will be much louder with headers. The high flow cats won't kill noise anywhre near as much as the OEM '87 cat system. Corsa's are good mufflers as are Magnaflows or even Walker SuperTurbos. Flowmasters will hurt your head with the resonance and noise.

ride250s

Lets say the LT Headers did cause me to loose a little low end torque. I would then probably gain some higher end horse power at WOT, right?

RandyJ75

I have a true dual exhaust system on my all stock '90, I bought it from Corvette Central, about $300.00 shipped. I have Magnaflow cats I bought from Hott Exhaust, about $130.00 shipped to my door. I had all of this installed by an exhaust shop, cost was about $200.00. The Corvette Central system has a cross pipe that acts like an "x" pipe already installed. System w/ Flowmaster 50's sounds great.

Randy

198T7VETTE

c4, was there any noticable differance in the switching of the stock style exhaust to the true duals. Low end loss or gain of power? Top end loss or gain of power?

198T7VETTE

Randy, same question for you...Did you notice any loss or gain from the exhaust swtich on a stock car?

c4cruiser

Because my 87 has a mild cam, some head work and port-matching of the intake runners, bored .030 over, and a chip, chances are that I gained some HP/torque at the top end but I have not done any dyno pulls with it. The OEM pre-cats and main cat with a rear Y-pipe was propbably restrictive enough that anything to clean up the exhaust was going to be a help.

I did a track day last month and the car seemed to pull better above 4000 RPM (I still have the stock exhaust manifolds). Low-end torque did not seem to change much at all. I autocross the car a lot and there is a definite improvement at mid-range RPM levels. But again, with the engine mods I have, it might be hard to compare my gains against astock motor.

I currently run Walker SuperTurbo mufflers as they were on the car when I bought it. The pipes are 2 1/4" as that is the diameter at the exhaust manifold flange. My muffler guy did not really recommend 2.5" as long as I have ths tock manifolds. I did add an O2 sensor bung just below the left side exhaust manifold as I do want the car to go into closed loop when I drive it on the street.

One thing that I have read heard about the L98 TPI system is that it does like some amount of back-pressure. Without some back pressure, the motor will lose some low-end torque.

On a completely stock motor, headers and a true dual free-flowing exhaust may not deliver big power gains. I would think that 15-25HP would be possible on a stock motor. The TPI system is somewhat restrictive and the stock motor does not make power above 5000 RPM. Even with the mods I have, the motor is pretty much done at 5200-5400 RPM. It will wind to 5800 in 1st and 2nd but I don't feel enough added power to run the motor up that high.

IMHO, if you want just a good dual system, go with the Corvette Central system with the X-pipe. It has an O2 bung and the 2 1/4" pipe will be OK. Add some good mufflers, and the car will sound great. If you want Flowmasters, get the 50 series. The 40 series will have tremendous interior resonance.

If you intend on headers, go with Hedman Elites, have a shop bend up 2.5" pipes, get a good X-pipe and your choice of mufflers. If you look at the pics, you may find there is not a lot of room for cats: bullet cats may be your only possibility there. Look for some that are no more than 5" in diameter and about 9" long. Pypes has some universal high-flow cats that will work.

ride250s

From what I can tell, Magnaflow has the best x-pipe and Metallic substraite cats. The cats are only about $100 each out of summit... Cant beat that for Spun Metallic substrait cats! Also x-pipe is bent to fit in a tight area as opposed to thers, and out of summit is only about $90 I think!

MK 82

Can't buy just Corsa mufflers. It comes as a system and includes the resonator.

I use EM long tubes, their extensions with Random Tech bullet cats, and the Corsa Cat Back.

Bolts right up.

To me, it is perfect.

You don't need an X pipe with the Corsa. The resonator serves the same purpose.

MK 82

No way you will lose power with LTs. The torque curve may shift a bit but you will gain HP on the top.

ride250s

I just like the way the x-pipe looks... haha I'm not much for that single resonator, so I will just have to sell it or something. What size diameter are those Random tech cats that you have? Are they a metallic or ceramic substrait? Do you have a picture of your set up?

MK 82

Are you going to lay on your back and stare at it?

If you ditch the resonator, you might as well buy Magnaflows.

ride250s

haha i may stare after hours...

its just something about the corsa sound that i like... its different!

MK 82

The resonator is a vital part in creating that sound.

ride250s

Do you have a picture of your system? I want to see where you have ur cats positioned. And how you have the y from your headers going into the resinator.

And who makes EM Headers???