So my exhaust front pipe recently broke and I am putting some thought into replacing the hardware because of how difficult it has been to remove. I had to cut both downstream bolts on the catalytic converter and got two of the three studs out of the manifold while still working on removing the broken third stud. On this I got a 1/4" hole drilled fairly close to center with an easy out mounted and almost have a clutched drill set up with a socket to torque the easyout after plenty of pb blaster and propane torching. Though if without success, I will probably drill the stud out completely and mount a bolt + nut since this happens to be a through hole anyway.

It seems possible to go with stainless steel hardware from ebay for about the price of zinc steel sourced locally. One listing has a set of stainless studs, though with zinc steel nuts and this made me wonder if all stainless would provide less holding power? Also, for the catalytic converter - front/intermediate tube joints, these m10x45mm bolts are comparable, but would the serrated surfaces would do well or is it is worth sticking with flat flanges?

Does anyone have a reliable source for this type of hardware?

 

Most Ace Hardware outlets have just about any stainless nuts and bolts you might want.

 

They probably provide zinc plated steel nuts because stainless hardware will cold weld to itself. Look it up. Stainless on stainless will gall up and fuse to itself, especially if both the male and female thread are the same grade of stainless. The two will actually chemically bond and be impossible to unthread without destroying the threads. It's slightly less likely if the two parts are a different grade, but not by much. A stainless stud/bolt with a zinc plated nut is the way to go for the pipe to pipe exhaust flanges. For the hardware between the head and manifold, I'd suggest getting a replacement set from somewhere like 22RE Performance or LCE. Those studs take a beating as far as heat cycling goes. The higher grade steel will hold up better than stainless. The stuff from 22RE Performance comes with thread adhesive on the end that goes in the head, and distorted thread locking nuts which will keep their holding strength even when heated.

 

Grade 8 yellow zinc bolts/nuts. My local hardware carries them. Check Home Depot, Lowes, and other hardware stores in your area. Also, just regular grade 8 bolts or metric 10.9 would be good too.

 

+1 for avoiding stainless on stainless. Too many times have I seen threads seize without ever applying a wrench. A standard zinc coated metric class 10.9 is more than sufficient, or grade 8 if you want to go with standard.

 

This is one other thing I was trying to figure out with installation of new studs -- whether to use a threadlocker/adhesive in the manifold; as the stud ought be stuck well enough to not come out with the nut, but not so well that it cannot be removed in the case of one breaking. Of course breakage is absolutely undesirable and actually had me considering a copper-based anti-seize on both ends of the studs. Does anyone consider doing this, or would there be concern for parts coming lose?

 

The hardware from 22RE Performance has an adhesive patch of something on the head side of the studs. It is red in color but I wouldn't equate that to red Loctite. I'm not sure Loctite is really what you want. You want something that resists loosening from vibration but it has to be resilient to heat. Loctite weakens with heat. And as you said, you don't want it to be so strong that the stud can't be removed if you decide that's necessary.

I'd recommend the kit from 22RE Performance for the manifold studs. It's worked for me on multiple engines and it's what they recommend/use. Each part and feature of that kit is chosen specifically for the application where they are being used. For the downstream connections, I'd recommend a stainless bolt and a zinc plated nut.

 

I have procrastinated ordering any hardware, but this morning came across these studs at the local Ace. Maybe these would be adequate over time or ought I hold out for something of a higher quality steel?

Grabbed some coarse m10 bolts and nuts to fasten the pipes to the cat, but only the nuts being stainless since stainless fuses to itself. Since I couldn't find any flanged hardware, is it best using lock washers on the nut or both sides?

Also I am guessing the anti-seize is applied between the stud and nut but not into the manifold?

 

Another real good source for hardware, along with a lot of tools and so on is McMaster-Carr. They have an on-line catalog that's really easy to search through for what you want. I buy all my soldering stuff, as well as crimps, and especially heatshrink from them. I've also gotten a lot of hardware from them. Nuts, bolts, wrenches for them, you name it. I use them extensively.

Just wanted to throw that out there.
Pat☺

 

Personally, I've not had the problem of SS nuts and bolts welding to each other on exhaust systems in either my 4Runner (cat bolts) or VW Bug (aftermarket 3-bolt collector flange). All have unthreaded without issue after years in place. YMMV.

 

As long as the studs are M10x1.25, not M10x1.5 which is more common in America, the studs could be used in the head. Those look like regular nuts, not lock nuts. The OEM stuff uses lock nuts to prevent vibrating loose. As everything expands and contracts, plain nuts may unthread. That hardware will probably be okay, but the set I've recommended a few times is better. It's up to you. The $55 price tag on a set of studs and nuts can be off-putting, but so is a blown exhaust manifold gasket due to a nut that disappeared.

The pitch on the flange hardware doesn't matter as long as the nut matches. I'd prefer a stainless bolt/stud and a steel nut. As steel rusts, it expands. So if the bolt gets rusty it can still get stuck in the stainless nut. In the opposite case, the nut can usually be removed or cut/split while saving the bolt. A wire brush will clean the stud right up and allow it to keep going. These are very minor details though, so you'll probably be fine with what you have. I don't have much faith in lock washers, but if you want to use one, I'd put one under the nut and use a flat washer under the head of the bolt.

I don't see a problem with using anti-seize at every threaded connection unless you use the studs I recommend, in which case anti seize would probably negate the usefulness of the patch of thread locker that comes pre-applied.

 

Honestly, neither have I at home. But I've seen it time and time again at work so I do what I can to avoid it.

 

I called 22RE Performance and he reports no value in using stainless anywhere -- says this and anti-seize will basically have no effect over the decades until the parts need replacing again. Stainless nuts on the studs would seem favorable at first glance, but the oem split nuts probably are best for keeping the whole thing tight.

One last bit that seems worthwhile is cleaning the threads on the manifold. Maybe just threading a bolt doused in oil back and forth then flushing them with wd40? Or maybe a different flush if WD would actually add to the problem? Probably paranoia about another broken stud but I imagine bunches of oxidizing bits of rust still hanging in there.

 

Jim's probably right.

You might be overthinking it but your plan seems fine. I'd probably spray some brake cleaner in each hole and blast it out with some air. You can make a thread cleaner by grinding a slot into a known good bolt. Make sure the slot is deburred so you don't ruin the hole you're trying to clean. A tap can be used, of course, but they sometimes remove a bit of base metal. You don't really want to remove metal, just the build up of gunk and junk in the threads.