exhaust manifold studs stripped - best way to remove?

[Wrench97]

Why would a Toyota dealership's parts dept have 5/16-24? Practically everything on Toyotas apart from spark plugs are metric. They were loose, not in a package.

Pic of nuts - new ones from dealer on left (top two didn't strip, bottom 3 did strip), factory originals on the right. They look like the same design to me. Maybe more chinesium in the modern ones compared to the ones from a couple of decades ago.

The plugs are metric too.

 

[john.k]

A while ago ,I replaced the head gasket on my Thailand built Ford pickup ...........I was very pleasantly surprised to find all the exhaust studs and nuts were a rustproof material ,with no trace of corrosion or jamming when unscrewed .

 

[joebass3]

I don't think you need to risk breaking the manifold studs by removing them.There looks to be a sufficient amount of good thread out towards the end of those studs that isn't damaged. Chase the 8mm x 1.25 threads, stack washers on the damaged section of the studs, and then install new nuts. I usually torque by feel on this type of job but I definitely think that 27 ftlbs is way high, regardless of what Toyota says. Buy new nuts and make sure they thread easily by hand. Not sure I would trust the nuts you have now after seeing the damaged studs. I would also use Anti-seize on all exhaust fasteners to lubricate the threads and prevent galling.

 

[CraigStu]

They may not be Toyota nuts. At the Lexus dealers I worked at there was a nut and bolt assortment bin that was maintained by an outside service guy who came by once/month to fill in the stock. The parts dept did have some specific nut bolts that were actual Toyota parts. But they had them because they were non-standard stuff that the outside guy could not supply.