Third Generation F-Body Message Boards

Third Generation F-Body Message Boards (https://www.thirdgen.org/forums/)

- Exhaust (https://www.thirdgen.org/forums/exhaust/)

- - Y-Pipe (https://www.thirdgen.org/forums/exhaust/744778-y-pipe.html)

Quick question: are the Y-pipes for the 305V-8 and the 350V-8 the same?
I'm offered a new Y-pipe for a 127KW 305 V-8, but i have a 350V-8 with a bit more horsepower....

The definitive post on 3rd gen exhaust by TransAmGTA350:

Quote:

Originally Posted by TransAmGTA350

There were only 2 different manifolds for the V8's throughout the years, but they were different depending on what motor and gearing package they came on. Here is the breakdown.

2" outlet manifolds with single 2 1/4" y-pipe
82-87 305 LG4 (VIN H)
88-92 305 L03 (VIN E)
82-83 305 Crossfire
90-92 305 LB9 w/o G92 axle (VIN F)

2 1/4" outlet manifolds with single 3" y-pipe
83-86 305 L69 (VIN G)
85-89 305 LB9 (VIN F)
88 350 L98 (VIN 8)
89 350 L98 w/o G92 axle (VIN 8)

2 1/4" outlet manifolds with dual 2 1/4" cats
89 350 L98 w/G92 axle (VIN 8)
90-92 350 L98 (VIN 8)
89 305 LB9 w/G92 Axle (VIN F)
90-92 305 LB9 w/G92 (Vin F)

The manifolds from the single 3" cat and the dual 2.25" cats are interchangeable. On the passenger side manifold, some will have the heat riser butterfly valve, some will have a spacer, and some will just have a donut gasket. You most likely have the wrong manifold for your application. If you have the larger manifolds, then it may be worth it to get the larger y-pipe for some more performance.

That Y-pipe is meant to be used with a matching set of headers - do you have headers or the factory cast-iron exhaust manifolds? If you have the cast iron manifolds then you will not be able to use that Y-pipe. I went through something similar with my own Firebird with the low output 305. I brought the car to a shop and they ended up exchanging the passenger side exhaust manifold with the one that was used on the 350 cu in V-8 - it sounds strange, but it has a different outlet configuration that allowed them to bolt up a Magnaflow Y-pipe. I see that you are in the Netherlands and I don't know if it is cost-effective but I want to mention that the passenger-side manifold and Y-pipe are still available. Here is the information:

Dorman exhaust manifold, part number 674519
Magnaflow Y-pipe, part number 16450

Hope that helps.

-Mike

I have these headers:

https://cimg1.ibsrv.net/gimg/www.thi...9d3fa43972.jpg

I need an Y-pipe for them, and I do have the single cat, and the #8 in my VIN...

I don't want to mislead you and hopefully someone with more knowledge of those headers will chime in, but...Those look like the Flotech headers, and there is a Y-pipe available, it is part number 1102YFLT. Note though that the Y-pipe looks like the GM factory Y-pipe which is not considered to be a good design (the diameter of the pipes coming from the flanges and the "merge" pipe are all the same; no true merge collector - the one pipe just "tees" into the other).

In the picture it shows 2 flanges; if it were me, then I would take it to a shop and have them build a "proper" Y-pipe (for example, something that looks like that Magnaflow one I posted earlier).

-Mike

Don't you think the Magnaflow Y-pipe will fit?

No, the Magnaflow Y-pipe will not fit those shorty headers that you mentioned in post #5.

So, what will fit my headers, any advice, besides the Flotech?

You either need the specific y-pipe for your brand/model headers or you need to make your own. There's loads of similar headers (headman and hooker shorties are nearly identical but the collectors are at different angles) and none of the y-pipes interchange.

Thanks.
I'll go to an exhaust workshop nearby, and have them fix me an Y-pipe.