Catalytic converter and collector

[94FSBlazer]

Hey guys,
new here. I have an exhaust question. I just finished putting a magna flow cat back system on my 2dr 1994 Chevy full size Blazer 5.7 350 tbi, to replace my completely rusted out stock parts. Now its on to my cat and y-pipe. My cat is rattling like crazy, and driving me crazy at the same time. So I have ordered a universal magnaflow cat, as well as flowmaster y collector. Here is the link to the collector -

https://www.amazon.com/gp/product/B001NRXA2O/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

So, my question is what else do I need. I am planning on going to a muffler shop to get the work done since I cannot weld in my parking lot. Im guessing it shouldn't be a big deal for them to bend up a y-pipe for me, but what about the O2 sensor?

Also, does this route seem logical or should I have just gone with a direct fit cat? I want to take care of as much of that crappy restrictive stock exhaust as possible, but wasn't sure how much work was going to be needed to make a universal cat work. Is the money i saved on those parts going to be lost in the labor to instal?
Sorry if this is a repeated scenario. I have done my research, but sometimes I just like to hear from others on forums rather than going thru so much of the general webpages for help

Thank you for any help you can provide!

OH! one last thing, I am not going to do headers at this point since my engine is not built up that much yet, so i do not see them as necessary, and my manifolds are still in decent shape.

 

[TigerEyz3]

Headers are going to free up a lot of the restriction you mentioned... the stock manifolds don't flow very smoothly at all, nor do they scavenge exhaust well (hence the restriction). Even with a stock motor, headers will benefit your performance - significantly more than changing the muffler. Not knocking you, merely stating the truth. I too started with changing the muffler - wanted a deeper rumble. As I learned more, I did better.

IIRC, the factory exhaust on your year truck has a y-pipe off the manifold downpipes, followed by single converter, followed by SI/SO muffler. The pre-cat O2 sensor should ideally be in the middle of the y-pipe so as to monitor the combined streams emissions info.

 

[94FSBlazer]

Headers are going to free up a lot of the restriction you mentioned... the stock manifolds don't flow very smoothly at all, nor do they scavenge exhaust well (hence the restriction). Even with a stock motor, headers will benefit your performance - significantly more than changing the muffler. Not knocking you, merely stating the truth. I too started with changing the muffler - wanted a deeper rumble. As I learned more, I did better.

IIRC, the factory exhaust on your year truck has a y-pipe off the manifold downpipes, followed by single converter, followed by SI/SO muffler. The pre-cat O2 sensor should ideally be in the middle of the y-pipe so as to monitor the combined streams emissions info.

Thanks for your input!
I was only leaving the headers out until later because I didn't think they would help that much with a TBI engine under 250hp. But it sounds like they can definitely help. I was planning on doing them later, but might as well get them done now. Maybe just some stainless shorty headers?

Someone suggested maybe just getting an off road y pipe and having the shop cut it and weld in the cat. Price wise, i can see this possibly being better, any thoughts?

And I think for the O2, I would have to get the bung installed on the collector, and convert it to the 3 wire heated. Im hoping this doesn't add a ton to the install price, but it is definitely necessary.

Ready to get this done! Wish I wasn't at a housing complex, and could do this all myself, but it is what it is. If I did go the off road y pipe route, I think most are direct bolt on, so we'll see.

Thanks again!

 

[TigerEyz3]

Shorty headers will be a drop-in bolt on situation (compared to long tubes and mid-lengths...both of which involve varying degrees of modification to the stock exhaust), that can give you some performance gains. As far as the header finish, personally I went with a quality ceramic coating for longevity purposes. However, you're talking to a guy that looks at mods from a "practical investment" viewpoint rather than a "show" viewpoint.

I don't have any personal experience with y-pipes as my vehicle has dual exhaust from the collectors to the muffler. That said, an exhaust shop should have no problems welding a y-pipe in. Not sure if it will be the off-road version given that you have to conform to emissions regulations ("off-road" typically means that emissions are ignored). Comparing an off-road y-pipe to a street legal y-pipe, you're typically just looking at an O2 bung being welded in to be street legal - they're inexpensive.

Good luck!

 

[94FSBlazer]

Yeah Im not worried about the looks of the pipes much either. I am in Michigan for a couple more years, so I need it to hold up. Ceramic sounds to definitely be the way to go with headers.
I was just thinking the off road y pipe as an affordable option that I would then cut part of the straight tube and weld in my cat. thinking maybe the price for just cutting and welding the cat in would be less expensive than putting the cat, collector and then bending the y pipe. Im not too worried about price to get this done, I just want to do it the better way and don't want to have to go back and do it again soon.
Thanks TigerEyz