OK. I am in the process of stripping an 84 Z28 with the l69 H.O. motor. Now will the exhust manifolds and y-pie be better then the stock lg4 stuff on my 89 RS vert. My friend said it will flow alot more. And it dose look like it. Now I know headers are the best way. But this car is not for speed. I have my IROC for that. But these parts are free. So if it's better then what I currently have. Should I swap them out. Now the RS dose have a 2.75 catback with a Flo-pro muffuler and a aftermarket cat also. Adam :-)

 

You would see a good amount of benefit over the stock LG4/LO3 using the L69 exhaust.But as long as you get the complete exhaust with the y-pipe and use a hi-flo cat and catback for the HO motor.

 

So the l03 would see a good improvment. It will be like this. L69 manifolds and y-pipe. Then ether a high flow cat or a gutted l69 cat. Then the aftermarket 2.75 inch flo-pro cat back. I will probaly change to a 3 inch flowmaster for a better sound later tho. So dose that sound like a winner? Adam :-)

 

Did it once upon a time. Do it. Check the Y difference:

https://www.thirdgen.org/forums/atta...tion-ypipe.jpg

JamesC

 

Dang!! I didn't know there was that big of a diffrence! So the y-pipe is a yes. But what about the exhust manifolds. Are they any better? Or do you have to use them to use that y-pipe. Thanks! Adam :-)

 

The manifolds are better (the same as the L98). To use the Y, you must use the manifolds. Catco makes a high-flow, four-bolt flanged cat for the L69 exhaust. Also recommended. Summit CTO-4116, IIRC.

JamesC

 

Since im on the same track also about to use l69 manifolds and y-pipe for my lg4....I checked that summit link, but they claim that the cat has 4" inlet/outlet? This must be a misstake, or isnt the y-pipe 3"?
Is it better to use this 4-bolt flange than getting a universal cat? The reason Im asking is that I will fabricate from the cat backwards...

sorry for jumping in like this..

Hasse

 

The above is the L69 replacement cat. The inlet and outlet is oval shaped as is the Y at the mating point. Check the pic of the Y above. This is a direct fit cat of the L69 system.

JamesC