4.9 exhaust issue and question (Page 1/3)
fierobear DEC 30, 11:49 AM
Ok, this may be a dumb question but since I’m not an automotive engineer I’ll ask it anyway...

I recently got a hold of a 4.9 to swap into a Fiero. On the stock Fiero engines, the exhaust crosses over to the forward side and goes down to the catalytic converter then continues on the bottom right side to the muffler near the trunk. The 4.9 crosses over the other direction, with the outlet on the trunk side. I understand that exhausts are tuned for engine timing and back pressure. Would it be possible to somehow reverse this so the exhaust dumps out forward so you can use the stock location of the cat and muffler? Otherwise, the cat, muffler and connecting pipes all have to be crammed into the space where the muffler is, and/or you have to lose trunk space.

Suggestions?
fieroguru DEC 30, 12:07 PM
Yes, this can be (and has been) done. Basically you make a cover plate for the current exhaust outlet off the rear manifold. Remove the crossover tube that connects the front and rear manifolds and fabricate a new Y pipe to route the exhaust to the stock Fiero converter location.





Will DEC 30, 12:11 PM

quote
Originally posted by fierobear:

Ok, this may be a dumb question but since I’m not an automotive engineer I’ll ask it anyway...

I recently got a hold of a 4.9 to swap into a Fiero. On the stock Fiero engines, the exhaust crosses over to the forward side and goes down to the catalytic converter then continues on the bottom right side to the muffler near the trunk. The 4.9 crosses over the other direction, with the outlet on the trunk side. I understand that exhausts are tuned for engine timing and back pressure. Would it be possible to somehow reverse this so the exhaust dumps out forward so you can use the stock location of the cat and muffler? Otherwise, the cat, muffler and connecting pipes all have to be crammed into the space where the muffler is, and/or you have to lose trunk space.

Suggestions?



You can cram all that into the space available with some tubing donuts and welding rod...
fierobear DEC 30, 12:19 PM

quote
Originally posted by fieroguru:

Yes, this can be (and has been) done. Basically you make a cover plate for the current exhaust outlet off the rear manifold. Remove the crossover tube that connects the front and rear manifolds and fabricate a new Y pipe to route the exhaust to the stock Fiero converter location.



Thanks, guru! That’s awesome. Was this a job you did? Do you have higher resolution copies of the pictures?
fieroguru DEC 30, 01:39 PM
Yes, this was one of my very early swaps.

Sorry, I don't have any better pictures... it was 17.5 years ago....
Johns 4.9 DEC 30, 02:37 PM
Are you interested in some headers for your swap?
Cheers
Spadesluck DEC 30, 06:47 PM
I highly recommend you to use John to build you some headers. The stock 4.9 stuff leaves a lot to be desired. Here is a picture of the stock stuff compared to what John built for me.



With this exhaust everything is routed just like stock.

[This message has been edited by Spadesluck (edited 12-30-2019).]

fierobear DEC 30, 08:17 PM

quote
Originally posted by Johns 4.9:

Are you interested in some headers for your swap?
Cheers



Yes, although it would be some time next year. I don’t know when I will begin the swap.

Also, I’m in California, I don’t know if those will be smog legal when I try for the CARB sticker for the engine swap. But you will be the first person I contact when I need exhaust. Thanks.

[This message has been edited by fierobear (edited 12-30-2019).]

Johns 4.9 DEC 31, 01:32 PM
Hello fierobear,
Looks like you are on your way with your engine swap. I am moving my shop to Arizona and I will have more parts for sale listed on my site early next year.
Good luck and I hope to hear from you in the future.
Cheers,
John

[This message has been edited by Johns 4.9 (edited 12-31-2019).]

Johns 4.9 DEC 31, 01:40 PM
Hey Spadesluck,
Thanks for sharing. I can't wait to hear your engine with those pipes! I'm almost done with my 180* headers and will be installing them soon.
Happy New Year.
Cheers,
John