Ordering a cat back for my dad’s 86 Iroc - 305 TPI car, automatic, single cat.

looks like flowmaster offers a 2.5” inlet that then flares to 3” intermediate pipe or a 3” inlet that stays 3” all the way back.

I need to find out which kit to buy- does anyone know what the outlet diameter of the factory catalytic converter would be?

I searched but could not find a straight answer.

thanks in advance for your help.

 

All 1985 to 1989 Tuned Port Injection Camaro and Firebirds came with the larger diameter High Output exhaust system.

There was the 1985 style that use a 4 bolt rectangular flat flange with an oval opening on the single catalytic convertor outlet. Also used on L69 5.0L High Output cars.

There was the 1986 to 1989 style that used a 2 bolt ball and socket flange on the catalytic convertor outlet. Also used on 1986 L69 5.0L High Output cars.

There was the 1989 to 1991.5 style N10 dual catalytic convertor style with a Y-pipe after the two catalytic convertors with the "Hog" style clamp, that is kind of like a V-band clamp, that connects to the intermediate pipe.

There was the 1991.5 to 1992 style N10 dual catalytic convertor style with a Y-pipe after the two catalytic convertors with a slip fit connection to the intermediate pipe.

There was the 1990 to 1992 style Low Output throttle body injection single cat exhaust system used on all Tuned Port Injection Camaro and Firebirds that didn't get the N10 dual catalytic convertor exhaust system.

All the other cars got a small diameter Low Output single catalytic convertor exhaust system except for the 1983 to 1986 L69 5.0L High Output cars.

The Flowmaster cat back you need for your Dad's 1986 IROC-Z is the larger diameter one linked below.

Flowmaster 17233 Flowmaster American Thunder Cat-back Exhaust System

 

The Flowmaster exhaust system is kind of pricey for an aluminized mild steel exhaust system with polished stainless steel tips.

If you are looking for the Flowmaster exhaust sound, then get the Flowmaster cat back.

If you are looking for a performance increase and a very nice sound, you can get a Magnaflow system constructed from 409 stainless steel with polished 304 stainless steel tips for the same money or less. You can also get a matching 409 stainless steel Y-pipe that will bolt right up to your factory cast iron exhaust manifolds and factory catalytic convertor and offers a significant performance increase over the absolutely horrible flowing factory T-pipe. Pair the Y-pipe and the cat back with the matching Magnaflow catalytic convertor and have a much better flowing system made from stainless steel with a real performance increase too.

Magnaflow 16450 | Chevrolet Camaro/Pontiac Firebird | Stainless | Mandrel Bent Front Y-Pipe

Magnaflow 93441 | Chevrolet Camaro/Pontiac Firebird | Rear | Catalytic Converter-Direct Fit | Stainless | Standard Grade EPA

Magnaflow 16829 | Chevrolet Camaro/Pontiac Firebird | Stainless | Mandrel Bent Cat-Back Performance Exhaust System

They have a 20% off Promo Code and FREE shipping in the US and Canada.

You can also get an "Up to" $75.00 refund on the catalytic convertor. Only chance you have of getting the full $75.00 is if the convertor you send them is the OEM GM "AC" factory original catalytic convertor in good shape that has NOT been "gutted".

Recycling For Refunds | Recycle Used Catalytic Converters | MagnaFlow

 

Thanks for the information- that was one of the two I was deciding between but needed someone that knew it better than I do to confirm.

i want the flowmaster sound, my 87 Formula 350 has the magnaflow and I don’t love it. It will be getting a TOTL exhaust next month if anyone wants the magnaflow muffler and tips.

 

I went back and looked at your past threads after I posted my reply and saw your beautiful 87 Formula 350. Read that it had the Magnaflow cat and cat back. Saw you had asked about gutting the cat for more performance and pretty much everyone said it's not worth it because it flows well.

If your Formula 350 still has the factory cast iron manifolds and T-pipe ahead of the cat I'd get the Magnaflow Y-pipe. It's a perfect fit and flows like gangbusters compared to the horrible factory T-pipe.


Magnaflow 16450 Y-pipe. This piece is night and day better than the factory crinkle crimp bent T merge pipe, and it fits in the car like a nice Isotoner glove fits your hand.


I love the Flowmaster sound. The performance sucks because of the interior muffler design. But they sound awesome.

I'm looking for a mild and mellow sound that opens up at WOT and I hope the Magnaflow will give me that. I absolutely hate the hideous exhaust tips that come with the Magnaflow cat back. I hate them so much I've already bought DynoMax 409 SS 2.5" mandrel bent tailpipes to replace them when I get my Magnaflow cat back. Already have the cat and everything ahead of it I need.

This Hooker system with the aero chamber muffler sounds pretty damn good to.

Hooker 16823HKR | Super Competition Street Force Cat-Back System Natural Finish Mufflers with Aluminized Pipes

 

What is it you don't like about the Magnaflow cat back besides those ugly exhaust tips?

Are you getting a old school original SLP TOTL cat back exhaust system or the new Hawks Motorsports version?

I might be interested in your old Magnaflow cat back depending on condition after you get it removed.

 

Thank you for the comments on the Formula! I’ve wanted that car since I bought my 87 GTA in 1994. There just aren’t many yellow 350’s… I think like 100 in 87 and a few in 88? Several more with the T tops and 305 but I like the look of the hard top and of course the bigger motor.

as far as the Magnaflow goes it’s the tips- makes the car look like a farm truck to me. They are hard to even look at. the sound is actually fine, although I do prefer the flowmaster sound. Everytime I buy something besides Flowmaster I regret it. Dynomax, Spin Tech, Pypes…. Always regret it.

Great call on the y-pipe. I will order that.

the TOTL is an extra original one I bought (when no one wanted one) for my 95 Firehawk. It still has the original tail pipes on it.

the Magnafow should be complete with the muffler and the god awful tips.

the Iroc I’m working on is my dads. We are the second owner and I think it has 60k miles. The old exhaust just rusted out internally in the muffler.

here are some pics of those two and a couple others we have.

 

Hi, are you looking to sell the stock exhaust?

 

First off a big thank you to Airwolfe for the info and link to the Flowmaster exhaust kit. Fit perfectly, looks and sounds great!

The 3” tips are big but look really good with the angle cut just below the bumper.

unfortunately the original exhaust was corroded and we found cracks all over it. The pipes were easily bent in half so we trashed it.