Help with factory correct exhaust restoration
#1
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Thread Starter
Help with factory correct exhaust restoration
Hey Thirdgen,
I have two 87 IROC's. both have 305/5spd. I am working on a technically correct factory restoration for the convertible. I want this car to be as close to all original as I can get it without having to refinance my house. I have found what the seller on CL describes as an unused original exhaust. But its just the portion rear of the CAT. I know I'll probably never find an original unused CAT so I will be forced to buy an aftermarket unit. So I have 2 questions. Anybody know which aftermarket CAT is closest to the original? And, I will be reusing the original Y pipe. But it is welded onto the current CAT on the convertible and bolted onto the CAT on my coupe. Which is correct? I suspect bolted on?
Thanks guys.
I have two 87 IROC's. both have 305/5spd. I am working on a technically correct factory restoration for the convertible. I want this car to be as close to all original as I can get it without having to refinance my house. I have found what the seller on CL describes as an unused original exhaust. But its just the portion rear of the CAT. I know I'll probably never find an original unused CAT so I will be forced to buy an aftermarket unit. So I have 2 questions. Anybody know which aftermarket CAT is closest to the original? And, I will be reusing the original Y pipe. But it is welded onto the current CAT on the convertible and bolted onto the CAT on my coupe. Which is correct? I suspect bolted on?
Thanks guys.
#2
Supreme Member
Re: Help with factory correct exhaust restoration
IIRC, the converter on my Camaro is a 3" slip fit onto the "Y" pipe (inlet) and a 4-bolt flange on the outlet.
Last edited by paulo57509; 08-01-2015 at 04:00 PM.
#4
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#5
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Re: Help with factory correct exhaust restoration
OK, I just read another post that was pretty convincing about the fact that there was never a 3rd gen that came with a 3 inch exhaust. The largest was supposedly 2.75. Unfortunately the post didn't say if there was also smaller pipes (which I assume must be true for the smaller engines?). Does anybody know for certain what size was stock for an 1987 305 with the 5 speed and the G92. I understand this combo came with a slightly beefier cam so perhaps this combo also got the biggest exhaust pipes of 2.75 inches?
#7
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Re: Help with factory correct exhaust restoration
on my 90 5.7, the factory cat-back pipe to the muffler was 3".
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#8
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Car: 1987 SC/1985 TA
Engine: 350/vortec/fitech
Transmission: T56
Axle/Gears: 3.27 9-bolt
Re: Help with factory correct exhaust restoration
Four bolt connection with gaskets was used on the L69.
#9
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Re: Help with factory correct exhaust restoration
Thanks naf!
good info. Anybody know the actual size of the intermediate pipe. There's one reply here but I'm getting mixed answers outside this forum. I understand that it was NOT a 3". I found an original unused intermediate pipe on CL but it is 2 1/4" and I think that is too small? I'm leaning toward it having been a 2 1/2" intermediate? Anybody know FOR SURE? I know it is a single cat and intermediate pipe not a dual.
Remember, it's a 5.0 with 5spd manual and G92. I believe that means it got the bigger cam and perhaps that has an effect on the size of those pipes?
I've been waiting on putting this phase of my restoration back together because I don't know what pipes to use to be as close to factory correct as I can get.
good info. Anybody know the actual size of the intermediate pipe. There's one reply here but I'm getting mixed answers outside this forum. I understand that it was NOT a 3". I found an original unused intermediate pipe on CL but it is 2 1/4" and I think that is too small? I'm leaning toward it having been a 2 1/2" intermediate? Anybody know FOR SURE? I know it is a single cat and intermediate pipe not a dual.
Remember, it's a 5.0 with 5spd manual and G92. I believe that means it got the bigger cam and perhaps that has an effect on the size of those pipes?
I've been waiting on putting this phase of my restoration back together because I don't know what pipes to use to be as close to factory correct as I can get.
#11
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Car: 1989-92 FORMULA350 305 92 Hawkclone
Engine: 4++,350 & 305 CIs
Transmission: 700R4 4800 vig 18th700R4 t56 ZF6 T5
Axle/Gears: 3.70 9"ford alum chunk,dana44,9bolt
Re: Help with factory correct exhaust restoration
In 89-92, 350 and 305 tpi 5speed (performance option) cars got the 2 3/4" intermediate pipe.
Others got a smaller pipe but I have never had any of those cars to know what the size is.
There were 2Y pipes for the V8 cars low and high performance sizes. Then in 89 the dual cat Y pipe came along and also changed how the catback intermediate pipe mounted up and also added a extra 10 hp..
Others got a smaller pipe but I have never had any of those cars to know what the size is.
There were 2Y pipes for the V8 cars low and high performance sizes. Then in 89 the dual cat Y pipe came along and also changed how the catback intermediate pipe mounted up and also added a extra 10 hp..
Last edited by TTOP350; 08-22-2015 at 12:39 PM.
#12
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Car: 1987 SC/1985 TA
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Axle/Gears: 3.27 9-bolt
Re: Help with factory correct exhaust restoration
I am in the process of swapping LG4 exhaust on my 84 to TPI exhaust but do not have access to stock I-pipe. I have the L69 exhaust on my 85, but again no factory I-pipe. The L69 y is certainly larger in diameter than the TPI exhaust and a good bit heftier.
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