Bolt size of the 3 Y-pipe-to-cat flange fasteners?

[fixizin]

Searched this forum, found about every bolt UPstream of what I'm after.

On the 3.0, it's the flange shaped like this: (rotate it 90deg clockwise in your head... recognize it now?)

i.e. to replace that gasket, I'm going to have to replace the very rusted bolts and nuts. I'd like to buy 'em before truck is out of action. Thanks in advance.

 

[fixizin]

OK, obviously what happened here is EVERYONE pounced in with the answer SIMULTANEOUSLY, which crashed the TRS/Jim Oaks/959 server... hope it reboots... lol.

 

[adsm08]

I usually just go buy a couple 10mm by 20 mm long bolts and nuts with some washers.

 

[fixizin]

Cool, thanks. I just figured the holes in the flanges were not going to be quite as large/sloppy as those in the gasket.

 

[trikerider]

Jeez, good luck getting the studs out of the cat flange the studs of my '94 V6 wrung into (lucky the 2 most inaccesible ones) and the bottom broke loose after a 3hr soak with PB blaster (this is good stuff)
the studs would not drive out of the flange I had to drill them and burnt up 3 drill bits doing it and used about a cup-ful of X19-A (another good canned lube) the studs are grade 8 and do work harden when they get hot.
but I got them out and drilled the cat flange to take 3/8" zinced grade 5 bolts whgicvh did fine I had to glue the topmost nut to a piece of rod bent in a semi-U shape to get it to the bolt.
if the tailpipe to cat flange is rotten good luck I had to 'adapt' a universal flange to fit I sawed the tailpipe in 2 pieces to rtemove. a biatch of a job

 

[AllanD]

If you heat the studs until they glow you can usually beat them out fairly easily.

Once you get them out you'll realize that they are essentially miniature "wheel studs"
with a serrated shoulder

But the original thread size is 10mm x 1.50

I replaced mine with Monel bolts and stainless steel nuts, smeared liberally
with Moly never-seeze, even though these bolts CANNOT corrode together.

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[fixizin]

OUTSTANDING technical and real life info! Guess since this joint is not leaking (AFAIK), and this was prompted only by my desire to do a rust-prevention paint job on the expensive cats, I'll figure a way to paint-in-place... got LOTS of masking tape, and a big roll of brown paper, lol.

 

[racsan]

i torched mine off some time ago & replaced them with 8 mm bolts i think. just had to do a clutch job & they were rusted badly, so i zapped them with a torch & when it was put back together i used 1/4-20 by 2" s.s. bolts. they hold it together good enough. , heck my flanges are gone on the Y pipe & are helt to the manifolds by 3 hose clamps each, one on both the manifold & the pipe, the third pulling the two together.