The stupid exhaust question thread

[Redbeard]

Are headers interchangeable from TBI to Vortec or visa-versa or do they have to be specifically for 96-98 5.7L?

If you have a TBI motor and swap to Vortec heads, how does this affect your header choice?

 

[joshjuniorr]

dont the vortec heads have a diff. exhaust port?

 

[MOBS]

To answer the O2 sensor questions:

As far as i know, all the OBS trucks had the O2 sensor before the cat, so removing the cat virtually wouldn't affect the O2 reading, but would lessen back pressure....if anyone finds an O2 after the cat, when you gut/modify/remove the cat, the engine will run extremely lean and altho it'll sound like it has a lunati 292 cam, it won't pull for squat, and it'll also bake your pistons.

 

[Clutch1819]

in the process of putting a gm goodwrench crate 350 in a 90 chevy stepside. originally had a 4.3 im lookin at gettin some long tube headers but not sure which ones to get. the engine is a replacement for pre-86 years. so would a set for like a 85 chevy truck fit with no problems?

 

[Clutch1819]

note that this is gonna be a carb set up. not gonna be tbi.

 

[ndians68]

To answer the O2 sensor questions:

As far as i know, all the OBS trucks had the O2 sensor before the cat, so removing the cat virtually wouldn't affect the O2 reading, but would lessen back pressure....if anyone finds an O2 after the cat, when you gut/modify/remove the cat, the engine will run extremely lean and altho it'll sound like it has a lunati 292 cam, it won't pull for squat, and it'll also bake your pistons.

not really, our truck has the o2 behind te cat and the cat is remove, doesnt have a cam sound... for long hopdefully and it pulls pretty well for the ole 350

 

[Mean Green]

not really, our truck has the o2 behind the cat and the cat is remove, doesn't have a cam sound... for long hopefully and it pulls pretty well for the ole 350

What year is your truck? If the cat is removed and there is an 02 sensor aft of the cat it is going to run lean, unless it's tuned out or a dummy or a bung is installed.

 

[MOBS]

The O2's before the cat are made to detect a richer exhaust than the ones after the cat. Removing the cat on newer vehicles will give the post-cat O2's a richer than normal mix, so the O2's will send an incorrect signal to the computer telling it that the engine is running too rich and the computer will lean out the engine trying to lean out the exhaust mix. It will run, but the chamber temps will skyrocket due to the lean condition causing hotspots in the chamber and can burn valves, seats, and prematurely wear the upper cylinder and the pistons(and upper compression rings). In extreme cases, it can cause your manifolds/headers to glow.

 

[ndians68]

What year is your truck? If the cat is removed and there is an 02 sensor aft of the cat it is going to run lean, unless it's tuned out or a dummy or a bung is installed.

1994... its not tuned or anything, but we bought the truck that way, we have had it on long trips and never had the manifolds glow or anything, the vavle guides did have something wrong but it was because the guy that owned it before us did it and like everything else he did it was messed up and the return holes for the oil back into the motor was messed up

 

[MOBS]

A 1994 with the post-cat O2 sensor?! What state was this truck originally sold? Reason I ask is because of the post-cat O2, I didn't realize until recently that ANY of the 88-98's came with those late-model O2 setups. Makes sense that I found a few like that in CA, but they were all 96+ models, never knew of any pre-96's with that setup. But yeah, if you tuned out or used the resistor trick, I bet you'll noticed an increase in overall performance, unless ofcourse you just have leaky injectors and that's what's keeping it from running like crap.