70 MACH I

Hey, while I'm thinking of it, does anyopne here have a rattle generated from their stock catalytic converters, when the system is hot and they hit 3000 rpm. My car's an '04 and still under warranty. Ford replaced one already (H-pipe, cat assy) , now I'm going back for another. I've got the H out of the car, you can clearly hear it rattle when you hit it with a rubber hammer. I wish to retain this piece on the car as I want to keep it emissions legal and generate a slight bit of back pressure behind the headers. Doe's anyone know if Ford offers a hi-flow cat setup? If so, maybe I can con one out of them on warranty?

John

Chopper

Get rid of them and get a high flow catted H or X pipe.You don't need back pressure.See if Ford will install the high flow parts free if you supply the high flow replacements.They should since it's a warranty job and they can still have the old parts to send back to Ford so they are reimbursed.Win win situation.I have a Bassani x-pipe and I like it.

mustang_montana

last year when i had some magnaflow cats welded in my o/r h pipe, the shop botched the job and put the drivers side cat too close to the fram. so they hammered the casing so it would fit and it rattled like that. it seems no midpipe fits my car very well with the new motor and bbk shorties. if its the casing on the cat they can just button it up or something.

MustangMafia

Then why not run open headers? Or no headers at all?

newb2000GT

I think he meant that you don't need as much back pressure as the stock converters provide. I think the high-flow cats on the aftermarket mid-pipes offer sufficient back pressure for good performance.