hi. I am in the process of purchasing a 1985 Iroc-Z and a question popped up about the duel cats. I know that they were not available on an 85 Iroc. I think it was like 88 or 89 that first had the Duel Cats. However, I assumed that they would go on any year 3rd gen since, well, they're all third gens. However, i went on Summitracing to see what my options were, and it doesn't list any duel cat setups available for an 85??? Is this just because they weren't available from the factory?? Did GM, for some stupid reason, change the floorpan for the duel cats on later third gens (i cant see this happening. but what do i know)? or whats going on?? I am very confused.

 

They're not listing it because it wasn't available in 85. A modern single performance cat would outperform the old factory dual cats anyway.

 

well i was contemplating duel modern performance cats and wanted to know if they would fit just like the 89 duel cats fit, except they'd be modren, performance, and on an 85 iroc

so would they fit with the same pipes, or would i need somthing custom?

 

Aperion is absolutely right. Also keep in mind that since power is limited by a dozen other things on your '85, running a single high-perf cat or dual high perf cats will not make a significant power difference until you address other power-limiting factors in your combo.

However, if you are determined to do the Dual Cat system, you will need the later high flow (large exit) exhaust manifolds & "y" pipe, or better yet headers designed for the '89-later dual cat system, plus a dual-cat specific after-cat exhaust, plus the dual cats. In other words, the entire exhaust system from the cylinder heads to the tailpipe will need to be changed, they didn't just change one pipe. However, all of that stuff will then bolt on, the floorpans did not change.

TA

 

thank you. that is all i needed to know!


you see. All the stuff you mentioned will be changed. First stop is the L98 in my info over there under my picture. It will be bored and stroked to 383 some time in the next year along with intake stuff, and i plan on getting some of Dyno Don's headers and whatnot. I was just making sure the dual cat setup will work like normal. The entire exhaust was already going to be replaced, i was just wondering what to replace it with.

Great, clear, perfect help man. thank you.

 

Yes, this is what to replace it with:


My header guy is now going to assemble them for me, so I should have a lot more available soon. He is going to make up 15 sets.

 

so they'll still be the same stuff that i've heard so much about but you'll have more?? thats good. I'm not sure of my financial situation over the next few months because of the holidays and the cars going to need painted etc etc but if i got some extra $ then i'll get in line for some! I've heard that they are wonderful exhaust pieces/systems.

 

I had just done some research on the subject, so I'm glad I could help.

Dyno Don headers & "y" pipe are an excellent choice for a modd'd 350 or 383, and he gives you the option of a "y" pipe to fit the dual cat exhaust.

C-ya

TA

 

power limiting factors such as?

 

He's probably talking about how, despite it was the first Iroc, the 85 wasn't exactly a ground shakinng, shelby crushing, import destroying beast lol. Plus, the TPI of course would normally limit the performance, along with the factory headers and cat-back. the list goes on. However i'm planning for the future so the immediate lack of advantages didnt worry me.

 

im just new to the 3rd gen....so all this info is quite helpful

 

ah! cool. well in that case, i'll elaborate allitte. As i've heard it, the main downfall of the 3rd gen Irocs and Z28s is the air flow, more specifically the induction and basically the whole TPI. While the TPI kicked some serious butt when it was new, it was still tuned to create monster low end torque, and its now extremely outdated. Most people here that don't have stock engines have some kind of modification to the TPI or induction, if not a full replacement of the TPI with minirams, superrams, stealthrams. just about any kind of ram . Therefore! thats the other drawback. a large 3 inch exhaust systems with aftermarket cats doesn't need duals to flow all the air, since the engine isn't taking in enough air to make use of the large exhaust system to begin with! So, honestly, i won't have any use for duals at first. However, since im planning some serious modifications, duals will be a good start for planning for the future, even though "other shortcomings" will lessen their usefulness for now.

hope i didnt mistake anything and give you false info, but i think thats a good overveiw!

 

DynoDon

Are your headers custom made?? they look like hookers. If they are custom made, did you improve the design for 3rd gens so the fit without all the extra crap needed to install SLP ?

 

Hey...extra crap? Did I get cheated, my SLPs didn't come with extra crap!!!

 

ok so i have a 350hp crate motor....built in phx,AZ

so i hear that 350cid's can handle a 150 shot.....then bringing me upto 500hp at wide open throttle.......

with all the excellent knowledge that LmSky gave....can i just run my hedman hedders with y pipe, 3in magnaflow HI-flowcat and chamered muffler dumped at the axle?


or should i plan for the future and do the true duals?

these cars are an addiction.... $1,300 for the car.......$130,000 to make it perfect

i dont wanna take awary from the original thread....move my post if needed..thanks