[hooki]

I just bought a new cat to fit up to my sierra. I've installed the ebay extractors which fit a g16b in a sierra so they clear the engine mount fine. The problem I'm facing is if I mount this new cat off the extractors then it will be hanging below the chassis rail and I'm guessing in harms way. I obviously want to avoid cutting up the brand new extractors.

The question is should I just mount as is in the picture?

or

Should I cut the extractors up to try and raise where the outlet flange on the extractors is? That should bring the cat up inline with the bottom of the chassis rail.

[sideways]

Raise it!! A ridiculously hot, venerable and not particularly cheap part is probably the last thing you want being the lowest part of your car.

You can't bend the extractors to bring the flange up?

Yesterday I managed to make some leaves smolder when I bellied out with just the pipe it's self. I was only bellied out for a few seconds but I was at WOT.

[atari4x4]

get a small dogleg bend made up

[Scrawny]

Hack a bit out of the extractors so it all ends up sitting higher

[atari4x4]

something like this...


i had the exhaust shop put a dogleg bend to tuck the muffler up well above the chassis rails on the silver one

[hooki]

I think that dogleg idea will work the best, thanks guys. I'll have a play around with it today and see how I go.

[alien]

what about doing it how they come from factory??? Mines a 2" cat... pretty easy to see in this pic, its tucked up under the chassis rails:

[jono165]

I made mine out of mandrel bends. I made a dogleg so I could have the cat mounted parallel to the chassis rail and then rotate the dog leg slightly to raise it up so its was flush with the rail. Offsetting it from the rail slightly allowed me to essentially run a straight pipe from the cat to the muffler. This also allows the gearbox to be removed without needing to take the centre section out of the exhaust.

I can post up some pics tomorrow if you like.

[hooki]

I managed to mount the cat today and it's tucked up out of the way . I first tried to bend some exhaust tube to make a dogleg but the shit bender of mine just made a mess of it, so I went ahead and chopped up my new extractors . I shortened the two primary pipes which seemed to solve the problem.

alien wrote:

what about doing it how they come from factory??? Mines a 2" cat... pretty easy to see in this pic, its tucked up under the chassis rails

I've mounted it in the factory position. I'm not sure if it's different between swb and lwb but my factory cat was mounted there. There's even the factory heat shield mounted on the floor pan to stop too much heat going into the passenger footwell. I've been told that cat converters run there most efficient when running hot, thats why car manufacturers mount them as close to the engine as possible (I'm not sure if thats true or not) .

[sideways]

Pre cat (1986) Sierras had the heat shield too, they had a muffler there instead.

Cats work heaps better when they're hotter. At school we built a go kart to compete in a CAMs fuel efficency/race thingy at Collie motorplex. A few schools competed, we all had to use the same engine (Honda GC160) and cat. One school mounted theirs really close to the exhaust and heat wrapped the lot. It won the emissions part of the comp by a stupidly large margin.