Looking for Stainless Steel Headers for a 98 305 that will bolt up to existing exhaust pipe.

[cubandeathgrip]

I found a ton that works for a 97 305.

Any other suggestions for a y pipe with a high flow cat to muffler?

thanks

 

[Nad_Yvalhosert]

96-99 (2000 Escalade & Denali also) are the same. If it works on the 97, itll work on the 98
The vast majority of the Vortec trucks used a dual pipe, dual converter assembly that ends at a flange.
The very rare, Federal emissions equipped, Vortec 5.0 y-pipe is kind of a unicorn. Never seen a replacement, performance or otherwise. It's likely gonna have to be custom made.

 

[cubandeathgrip]

96-99 (2000 Escalade & Denali also) are the same. If it works on the 97, itll work on the 98
The vast majority of the Vortec trucks used a dual pipe, dual converter assembly that ends at a flange.
The very rare, Federal emissions equipped, Vortec 5.0 y-pipe is kind of a unicorn. Never seen a replacement, performance or otherwise. It's likely gonna have to be custom made.

thanks
if the 305 is the same as 350 in dimension ( except in bore size.) Could i use the dual converter assembly from a 5.7 on this truck?

 

[L31MaxExpress]

Every 4.3 and 305 GMT400 Y-Pipe I have seen is like a TBI Y-Pipe and uses a single cat. Magnaflow makes a nice higher flowing unit.

Could use a 350 one, but its still restrictive and the 02/catalyat configuration in the tune needs to be changed.

 

[tayto]

L31Max, does this also apply for the 88-95 units as well? I removed cat on a 92 GMC recently and noticed at idle it wouldn't go into closed loop anymore. added a 3 wire o2 and it seemed to solve that issue, but is there stuff that should be changed in the calibration?

 

[PlayingWithTBI]

I removed cat on a 92 GMC recently and noticed at idle it wouldn't go into closed loop anymore. added a 3 wire o2 and it seemed to solve that issue

Yeah, with less restriction your 1 - wire O2 didn't get hot enough at idle to work. The heated O2 doesn't rely on that.

but is there stuff that should be changed in the calibration?

With only one O2 sensor, your PCM doesn't care what's going on downstream. But, a tune will always help with proper SA and AFR after your modifications. You can even get better performance with a stock system too.

 

[tayto]

Ya, my general TBI "recipe" is to put a 3 wire O2 on regardless. this truck has 200,000 miles on it and was the original O2, time for a replacement! I haven't done any tuning in sometime, so just trying to do small things in the tune for now. It's a friends truck and planning on a MTC1 cam swap that he's had sitting around for a while and I want to try a single plane intake Fast355 recommended me on gearhead-efi a few years back. it's an old holley street dominator "Z" series with a funky runner that connects #7 & #8

 

[PlayingWithTBI]

I want to try a single plane intake Fast355 recommended me on gearhead-efi a few years back

Yeah, your name looked familiar

 

[tayto]

not to get hijack, but did you ever get your single plane dialed in??

 

[PlayingWithTBI]

not to get hijack, but did you ever get your single plane dialed in??

No, I didn't go that route - yet, ha ha.