97 5.7l do I need both cats?

**thedipstick** · 08-28-2010, 06:20 PM

I have a 95 5.7l and I am doing a vortec swap (crate motor). I have a donor 97 for all the parts I need, it has 2 cats coming off the y pipe but I have a new custom exhaust on my 95 and really don't want to scrap it. Do I really need the 2 cats or can I use my 95 exhaust, y pipe and just add the bungs for the extra o2s? I know I should use both o2 sensors right?

Thanks in advance.

**thedipstick** · 08-29-2010, 03:08 PM

Anyone? Also does anyone know if I need to swap out the harness behind the dash?

**907 Chevy** · 08-29-2010, 04:20 PM

No you don't need the 97 Y pipe if you're just swapping the motor and you won't need the harness if you're planning on keeping it TBI.
The extra O2 sensors are required to tell the newer PCM's if the cats are functioning properly.
The 7427 PCM in your truck doesn't give a sh!t if the cat is working or not so you can keep your exhaust exactly like it is.

**thedipstick** · 08-29-2010, 04:32 PM

Thanks for the help, but I am not keeping the TBI sooooo

**907 Chevy** · 08-29-2010, 05:36 PM

Thanks for the help, but I am not keeping the TBI sooooo

What are you gonna be running?

**thedipstick** · 08-29-2010, 05:57 PM

I have a 95 5.7l, the engine was tired with 211k and I was looking into getting a new motor when I came across this 97 with a fresh gm crate vortec 350. Shortly after he put it in he was involved in an accident. So I bought the entire truck for the swap. I have my old motor out and sold, ecu, harness and all. I know that the ecu is moved to the engine bay and the harness still runs to the firewall on both sides just not sure about the exhaust and the dash harness.
Thanks

**907 Chevy** · 08-29-2010, 08:06 PM

Well in that case ignore everything I said in the previous post.Unless you're gonna get the rear O2's deleted with a tune you need to either keep the Y pipe or weld in more O2 bungs on your new exhaust.

**thedipstick** · 08-29-2010, 08:14 PM

Ok cool thanks. Ya I just didn't want to gave to buy another high flow cat and get all the exhaust all re done. But it may be easier I guess.
Anyone have an idea about the dash harness? I have been searching forums and the web like crazy. I'm sure someone has done the complete swap before. Didn't think it was going to have so many differences. But at least I have a full donor truck to pull parts from.