Just pulled stock cats out and put after market pipes. Bolted up but loud at driver side flange. Felt air coming from flange. Loosened bolts, adjusted, same thing.

My guess is the nut on the re-used bolts may be rusted stuck and new flange may be different thickness and nut is not tightening down enough?

Any idea where to get new 8mm stud bolts and nuts to replace them?

Anyone experience this before? Not mating up all the way with re-used bolts?

Thanks.

 

I found the Ford Studs are the same thread size (8x1.25 or 8x1.50 if I remember correctly). You can buy a complete set with nuts normally at any good auto parts store under the help section with misc parts. The studs will need to be cut down (longer than LR studs, but that's a quick and easy thing to do vs wait for the OEM ones to arrive from AB or Ebay.

 

Good to know. Will definitely give that a try. Thanks!

 

No problem at all, and you can always add a few washers to the OEM setup to see if that makes it seal up. If not, I'd inspect the cat flange for being 100% flat if the washers don't help. I've never really had issues with the two front gasket area's besides the darn stud/nuts snapping off during removal.

I've always had issues with the rear section sealing up to the muffler on the aftermarket setups.

 

Was thinking washers too in the interim. Great minds must think alike. :-)

 

I have the same problem with an aftermarket y pipe. My solution was doubling the gaskets.

I got Davico. Cheap, but I had to do alot of redneck engineering to make it quiet and keep the cat off the driveshaft.

 

That's a real good tip!

 

Did doubling the gaskets quiet it down at the flange?

 

Yes. Worked like a charm. I had a new set and just put the old ones over them. I could not find a way to get enough leverage to bend the pipe/flange in so that was my desperation move.

 

Well, had to pull the whole new Davico Y-pipe back off and put the old one back on. Yay.

Driver side flange was not to spec. Did not have the proper angle to mate. OEM had more downward angle. Not sure if you can tell in the pic.

Now to either cut those cats off the new and weld to the old. Or return to RockAuto if possible and get 2 new cats to cut and weld on. Pipes are good. Just bad cats.

Look at the flange on the far left and far right.


Also, I got the Dorman 8 x 1.25 studbolts but aside from too long, the buffer is too wide between threads. The exact match was actually listed as water pump bolts. Dorman 23737. I used acorn nuts from the other kit.