73 E-Type Exhaust manifold studs

Hi, I recently removed my exhaust manifolds to replace the gaskets, all the studs came out of the head, nuts appear pretty well rusted solid. I was wondering in the interest of time if I could make my own studs out of ready rod, all coarse thread or is there something special about metallurgy of the studs and having coarse threads on one side and fine on the other ?

Cheers,
Steve

Soak them in vinegar for a day or so to see if the nuts free up.

Good idea, the head side has perfect threads, someone in the past put silver anti seize on them, the other side is nasty. A couple are trapped in the manifold flange, I’ll try double nutting the other end.
Cheers,
Steve

Assuming that’s the all-thread rod one commonly finds in hardware stores, I’d say no. Most threaded rod you will find is ASTM 307 low carbon; Grade 2. I’d guess the exhaust manifold studs are at least grade 5.

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Hi Steve,
Someone versed in engineering will correct me if I’m wrong, but I’ve always been taught that the use of coarse threads on one end of a stud and fine threads on the other end is to facilitate removal of the nut as opposed to having the stud back out. This obviously didn’t work in your case because the coarse threads were treated with anti-seize, while the nuts were left to rust in place.

Moving forward, I would suggest using the proper studs, being sure to treat both the coarse threads AND the fine threads with a heat-resistant anti-seize.
All the best,
Jay

As someone who has no E-type I find this hilarious! These studs (which I bought recently) are among the very few E-type parts that are relatively cheap. Just buy new ones. If you want to spend several bucks each, buy stainless. :slightly_smiling_face:

I would think the studs are at least grade 5, perhaps a formula that resists heat although maybe I’m over thinking it. The coarse thread goes into the soft aluminum head, the fine for the nut which would allow more torque to tighten although I would think the weak link is the aluminum side. I need to check what the tightening torque is, if it’s the coarse or the fine torque. Cheers, Steve

Yeah I know, about $2.50 each plus shipping but I wanted to show the car next Sunday.
Cheers,
Steve

FWIW I removed a factory turbo on a Honda motorcycle built in 1982. Bolts to the manifold were 8 or 8.8.

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The studs are not unique to Jaguar or XK engines. Do you have a NAPA auto parts store near you? I’d be surprised if they didn’t have the studs in the correct size. Ace hardware stores also often carry a lot of specialty fasteners like the studs you want.

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That’s a good point, I’ll give some parts stores a call, may even have exhaust manifold gaskets, possibly a standard size.
Cheers,
Steve

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The coarse thread is because it has to go into an aluminium block - trying to cut a fine thread would simply chew the block up.

If doing this in situ, free space is so tight that a couple of the studs actually hinder your taking the manifolds off, so the studs coming out with the nut is actually helpful. To refit, you’d have to thread those studs back in once the manifold is partially (loosely) fitted.

kind regards
Marek

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Yes it was a awkward job, the manifold is in the way for the top nuts, you have to use a open end wrench coming in from the sides, but I happily discovered the bottom nuts which you can’t see are accessible via a socket. I was able to find studs locally, but they are a bit too long each side, so I will cut them and get the car together soon. Thanks for everyone’s replies and suggestions.
Cheers,
Steve

Oh one last thing, does anyone know the torque spec for these studs ? I don’t see one in my manual, whether the torque is for the 18 tpi threads or the 24 tpi threads where the nut is. Either way I will be applying some copper grease so the torque will have to be decreased to compensate.
Cheers, Steve

I don’t think there is a published torque spec short of “Don’t strip the aluminum threads in the head”. :grin:

The studs just need to be firmly snugged up in the head. For the nuts holding on the manfolds I’ve always done it by feel; watched the lock washers and stopped turning the wrench just after the lock nuts were fully compressed.

OK will do, I did find in my travels ‘repair’ studs with oversized ends to go into the head !
Cheers,
Steve