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Manifold stud threads.

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B

burgundyben

Jedi Hopeful
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On my MGA the nuts holding the manifolds onto the head are brass, a 1/4 whitworth spanner seems the best fit.

On the 1800 B engine that is going in the brass nuts dont feel quite right.

what thread on a MGB 18V manifold stud?

Thanks again!

BB
 
Probably good old SAE sizes for the MGB engine.
 
Absolutely SAE. 5/16 NFT, IIRC.
 
National Fine thread... UNF is likely a more correct term. Sorry for the confusion.

The studs may have coarse on one (head) end, fine on the other, too. Can't recall and ain't gonna pull one out just now. :wink:

But they're 5/16" fine at the exposed ends.
 
The ones on my 65 head are fine on both sides. Replacements are usually coarse on one side, fine on the other.
 
5/16-24, as mentioned on both sides, you'll not find these studs to be run of the mill, meaning you can't noramlly find them at your local fastner stores, luckily you find them readily available at your normal MG parts vendors.
 
I just had to deal with this as my furthermost rear outer stud was loose (due to a cross thread) and making a racket, I had to remove it but I had a spare from Moss, I always order spares (tony said it was better that way). Anyhoo my MOSS #328-900 has different threads, 5/16 18 on the inner end and 5/16 24 on the exposed. What is the conflict here, before I go and tap my cylinder head to accept the new stud. Do I receive the wrong stud?
Mike
 
The best thing to do would be HeliCoil the stripped head with a 5/16-24 insert and find the correct stud, Mike.
 
Indeed helicoils are excellent.

I got to the bottom of the mystery on my car, the studs are 5/16 UNF both ends, the old brass nuts are 5/16 UNF, but they are not 1/2 AF spanner size, they are a bit bigger! 1/4 whitworth spanner was a good fit.

New brass nuts are 5/16 UNF and a 1/2 in spanner fits.

Smart!
 
Elitist! :jester:
 
They're a full insert, a sort of self-locking thread replacement "sleeve", where HeliCoils are a hardened wire system, open wound into a larger tapped hole. The HeliCoils can be a bit of bother setting them compared to the Timeserts. If you need flush threaded holes the Timeserts have to have the hole they're wound into relief cut for their shoulder.
 
On the same thread I just discovered that one of the inner studs is stretched to the point where it's almost hourglass shaped, really amazing. How do you get these bad boys out when they're not crossthreaded and loose? pb and drill a hole through the diameter for a lever of some type?
 
spin 2 nuts down over the exposed threads, tighten them against each other as hard as you can, then turn the bottom nut to spin the whole stud.
 
The "double nut" method works most of the time, I prefer a "sprag" type stud removing tool. It applies the force/torque closer to the threads and across more of the stud surface than two nuts. An excuse for a new tool!

If you have "hourglass" shaped studs, Mike, that's amazing... and scrap. Who was th' gorilla wot torqued THAT down??!?!? :jester:
 
Yes, stud sockets do make life a bit easier, plus as mentioned, a reason for some new tools :smile:
 
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