Odd bolt size?

I'm tearing down an '81 200, and the exhaust manifold bolts are rusted on pretty well. I've been soaking with PB Blaster for a couple of days and no luck. Next will come the torch. But my question is this: what size are these bolts? My 1/2" socket is too small, 9/16" is so loose I'm afraid it'd strip the heads. I can squeeze a 14mm open end wrench on it, but not a 14mm box end. Could it actually be 17/32" bolt, or is it a 1/2" that has swollen with the rust?

They were 9/16. I would get a 14mm impact socket and drive it on with a hammer. Then bump it a few times with an impact wrench turned down low. If you can get it to move, bump on out.

You might have to use heat to get them loose. Good luck.

I have had that happen with exhaust bolts before, its because the sort of erode in layers. Just wack the closest snug size 6POINT socket on it and gently try rocking it back and fourth. I would not try the impact unless its moving. Slow and steady back and fourth and I would not use anything larger than a 3/8 ratchet, anything larger and you will easily be able to break it. Keep adding the heat and pb. Drilling those things out is a real time consuming pain in the butt so even if it takes a long time just take it slow.

Good to know I'm not going nuts. (At least not about this!) I'll be trying the heat tomorrow.

I had to drill out 5 exhaust bolts on the motor I just built.

Use PB Blaster or at least WD-40 when taking them out. A 14mm will be just a little more snug than a 9/16 but they are very close. To tell the truth I sometimes use a 14 when I don't have a 9/16 handy... but thats mainly because I don't have a whole lot of SAE tools.

i just started tearing down my engine (YEAH) i used evaporust from harbor freight. it did a great job. my engine is from a 77 grananda.