Pre cat removal again

[steve-V8s]

Please can someone explain how the pre cats are held in and if you took yours out how did you do it ? Presumably they were manufactured in the cylindrical part of the manifold and are bonded in place somehow. I am still undecided about taking them out, have had a tentative poke with a chisel and was surprised how robust they are. Tried passing a length of plastic conduit down from the other end and encouraging it to move but it remains solid. Can see that the obvious way is to open the cylinder, take it out and weld up the wound. Am a bit nervous of that approach because of loosing alignment with the Y piece. Trouble is it seems to be one of those jobs that once you have started there is no return.

[Pupp]

You're right that it's a one way job once you've started. Big drills, bars, and the best thing I came up with was a sharpened steel pipe (like a circular chisel). You'll need to destroy the matrix to get it out. Wear a mask.

My Aussie neighbour saw me doing mine and wanted a go so I left him to it with a couple of Grolshes...

[scotty_d]

Pupp said:

You're right that it's a one way job once you've started. Big drills, bars, and the best thing I came up with was a sharpened steel pipe (like a circular chisel). You'll need to destroy the matrix to get it out. Wear a mask.

My Aussie neighbour saw me doing mine and wanted a go so I left him to it with a couple of Grolshes...

Like it, i want a Aussie Neighbour too now work

[Rascal661]

I used an SDS drill to get the precats out. Took quite a while but got there in the end. There were a few small shards left stuck to the edges of the manifold which were difficult to remove, but a dremel with buffing wheel took them off.

[clive f]

if you go for the cut and re weld option, cut directly into the weld that joins the 4 " pipe to the 4 into 1 section, before you cut, scribe 3 straight lines across the weld onto both surfaces, each line being roughly a third of the way around the outside of the pipe ie, 12 oclock, 4 then 8 oclock then when you line it back up just line up the 3 lines to eachother and your y piece alignment will be okay, also make sure for best results to use a cutting discs 1mm thick, in a hand grinder, the neater and narrower the cut the more accurate the y piece alignment will be.

[LordGrover]

Have a look at crazycraig's post here.