I had a little garage time this weekend, and installed the speedo drive
gear scrounged for me by one of you listers, rearranged the brake booster
vacuum line and check valve misinstalled by the mechanic, and attempted to
scrunch up on the nuts holding the cat converter to the mainifold to stop
an exhaust leak. I have had to do this a few times over the winter, and I
know that they are stripped. One nut was missing, and when I tried to
tighten the other one that was loose, it just spun. I removed that nut,
and discovered that it was brass. Should it be? Also, I tried to find a
nut to fit, and was unsuccessful. Is this the Witworth standard raising
it’s ugly head? Hex head, that is. The hex is a 9/16. In SAE, a 3/8-26
(UNC) and a 3/8-24 (UNF), both use a 9/16 head. Neither fits the
studs. Anyone know what the thread is on the studs?
As an aside, my guess is that the “mechanic” used the brass nuts as
self-threading nuts, so he wouldn’t have to find the right ones
Thanks!
Dave Spalding
79 XJ6L Series II Federal, USA model
3/8-26
(UNC) and a 3/8-24 (UNF), both use a 9/16 head. Neither fits the
studs. Anyone know what the thread is on the studs?
They should be 3/8-24. Maybe the threads on your studs are messed up from
having stripped nuts. Brass nuts would be better than steel since they do
not rust on.
Phil_________________________________________________________________
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Brass nuts would be better than steel since they do
not rust on.
Phil
Interesting, Phil… Would it be good policy, in your opinion, to replace
steel with brass when making changes/repairs, e.g. manifolds? No
‘dissimilar metals’ problems?
The SII XJ12 has such brass nuts on all 16 studs that hold on the cat convertors…I
found suitable brass replacements at Eagle Hardware, which is no more…8-(…
Jay Gilmour wrote:
Brass nuts would be better than steel since they do
not rust on.
Phil
I bought a set of genuine exhaust manifold to pipe nuts from Jaguar in the
UK years ago and they were steel nuts that had been helicoiled. The
stainless coil insert wont rust onto the studs. They were a little expensive
but effective.
The correct (factory) nuts for the SIII converter-to-manifold flange are
special: plated alloy steel with slightly triangular-shaped stainless-steel
helicoils. The triangular shape acts like a locking nut, and the SS thread
minimizes oxidation. I bought some recently from an aftermarket Jag
supplier, and they cost about $4.00 each. Plain brass may work well also,
except they should have SS lock washers under them. FWIW, the E-type
typically uses brass nuts on the exhaust manifold flange.
Thanks guys and gals
The collective advice: Threads should be 3/8-24. Some XK engines had
brass nuts from the factory. If you’ve got brass ones, use 'em. (and I
know some of you guys got brass ones ) Stainless is good, Jag sells
carbon steel nuts with SS inserts used on later models. Some of you use
brass washers, some use SS washers. Clean the threads and use high
temperature grease.
Thanks again.
Dave
79 XJ6L Series II Federal, USA
) Stainless is good, Jag sells