91 LS400 Cats

[Boyscout]

I have a 91 Celsior (LS400) and bought the S&S headers. the 3-bolt flange on the headers is the wrong size and the tube lip on the cat is a bigger diameter than the header exit, so it wont go together.

My options are:

1) put in de-cat pipes
2) get some flanges made & put in some universal high flow cats


either way, i need to know this info:

the measurement from flange to flange? (length)

the diameter if the tube lip on the 3-bolt flange side?

Also, it would be a great help if someone could trace the flanges and bolt holes onto a piece of paper and email it to me (or post it here). you will need to draw a 1" reference line on the paper so i make sure it is printed the right size. that way i know for sure it will fit.

I would greatly appreciate the help.

thanks

 

[dicko]

I have a question regarding this. If you were to gut or remove the cats, would that not mess around with your secondary O2 sensors and change the way the ECU manages the engine? or does the ECU learn and adjust the A/F ratio accordingly?

 

[Boyscout]

I have a question regarding this. If you were to gut or remove the cats, would that not mess around with your secondary O2 sensors and change the way the ECU manages the engine? or does the ECU learn and adjust the A/F ratio accordingly?

I only have one set of O2 sensors, they are in the header before the cat. The sensors after the cats are EGT probes to tell the ECU if your cats are working properly.

So in my case I would be fine. Im not sure about the LS400 though, it might have two sets, for emissions regulations. (my Celsior also doesnt have the EGR system, which the LS400 does have)

 

[Tempeheat]

it didn't mess with mine. I removed the cat and put a straight pipe in place of them with the 4 O2 sensors in their factory place. 92 LS400 The Platinum in the cats is worth around a hundred dollars in scrap metal.

 

[dicko]

Any impact on performance? I'm thinking that is what i'll do, if the secondary o2 sensors are largely useless anyway. Getting it tuned could always fix any problems caused i guess.

 

[Tempeheat]

I think so, it was hard to tell since I put the Lextreme converter in at the same time and also removed the two front mufflers. It sounds good.