Downpipe/Pre-Cat stud - supposed to look like this?
 

This is the top-rear stud from the pre-cat. It was difficult to extract, but I took my time and was careful not to shear. Once I broke it free, it spun rather smoothly for about 2 and 3 1/8th turns; then it seemed to sieze up. I soaked it with PB and left for a day. After I came back I was able to work it back and forth and finally got it off. It was "tight" the entire way I was unscrewing it, it only came loose at the final few threads. I might mention that of the 4 total studs, only this one came out; the others the nuts came off rather easily and the studs are still in the car. I am unsure how to extract them.

My question is, is this supposed to look like this? Two photos are shown, one of me trying to get a look at the bolt with my camera, and the other once I had it extracted.

Unrelated rant: I am having a very difficult time getting this pre-cat off, the more things I remove, the more I see wrong with my new car and it is very demoralizing. Busted vacuum hoses, busted check valves, the coupler at the Y-Pipe was gashed. I am surprised this thing ran and idled so smooth, but at the same time, wary of what else is busted that I am not seeing.
https://cimg7.ibsrv.net/gimg/www.rx7...432c39e02e.jpghttps://cimg6.ibsrv.net/gimg/www.rx7...7e1bbc64d2.jpg

Looks like a pretty normal used exhaust stud to me. I wouldn't re-use it, but I don't see anything alarming. Just chase the hole with a tap and new studs and copper nuts with plenty of hi-temp anti-seize before reassembly.

Edit: I get the frustration sometimes. I just put my car on the lift the other day and found oil leaking from a stock differential bushing. Doesn't look like a fun job. Then I have to remind myself that these are 25 year old cars that were a little finicky when new...and order parts and move on.

Thank you for the reassurance. There was evidence of rubbing on the fat part of the stud, so I was worried I had ground some threads flat. Do you know the tap size and pitch?

Also, I have wet oil on my compressor housings and some of the hoses. Hard to say where it is coming from. Also some around the oil pan gasket. I wouldn't be so upset if I wasn't a neutered man living in an apartment; where my maintenance options are limited.

There is a thread showing all the stud sizes, search around a bit for it.

If you only need one stud and the other 3 are fine, I would just get a new one from Mazda. If you have to do all 4 I would just get aftermarket studs.

For the nuts, get these -

M10-1.5 Exhaust Lock Nut Copper Plated Steel 14mm Hex

That's a pack of 25 so you will have plenty. I've been using those nuts for years, they work awesome, stay put, and don't destroy the studs when you need to remove them.

Dale

Thank you both, my downpipe came with SS bolts and I think i have to use those. Any tips for getting the bolts at the main car loose? They seem to be most difficult yet easiest to reach.

What downpipe did you get? Some of the US-made downpipes require you to replace a stud with a bolt.

For the main cat studs, they just require some elbow grease. Worst case, if the stud breaks, drill it out and use a bolt and nut to secure that flange instead of a stud and nut. Heat and PB Blaster are your friends.

Dale

ATR Downpipe and midpipe. I will be selling the midpipe, as I want to keep this car as close to OEM as possible. I'm only doing this downpipe to get the heat out of my engine bay. I might have a high flow cat welded into the catback exhaust (looks aftermarket) if I have issues with emissions.