Show whole topic Jun 13, 2018 5:37 pm
Hugo Offline
Member
Registered since: Mar 30, 2018
Location: -


Subject: Re: Exhaust Manifold Gasket
Interesting - I think you mean you have 5/16 Whit studs, not 1/4 Whit; the confusion arises because Whitworth nuts used to be one size larger across flats than BSF. Then, I think it was in WWII, they 'shrank' the Whitworth nuts to the same size as BSF nuts, in order to save metal. Hence you have dual markings on spanners; 1/4W = 5/16 BSF etc. Except that this is no longer accurate either, since 'modern' 5/16 Whit and 5/16 BSF nuts are the same size across flats. That in itself is a very weird size, 0.513" or some random figure like that.
Anyway, to return to your problem - presumably you have just been tightening the nuts on the (incorrect) threads, rather than pulling the manifold up tight against the block? In a way I'm surprised they still managed to work loose. If it were my car, I think I would try to rescue the threads on the studs if possible. Can you run a die-nut down the studs to retrieve a passable thread? Either BSF or Whit, whichever is most likely to work. Then get some long brass nuts & hope they will tighten up ok. If it doesn't work, you're only back where you are now anyway.
I've just had the job of drilling out all fourteen bolts that hold the water jacket side-plate on. The previous owner had started removing the steering box & dynamo to do this (it had corroded through) but sadly he did not live to complete the job. I pulled the engine out & did it at eye level.
I also had one of the exhaust studs snap off when I pulled the manifold, & I managed to drill it out ok. It had to be a top one too, right up against the cam housing, and I JUST managed to drill it straight by putting a drill bit in the chuck about 1/4" deep and then the drill bit was JUST long enough to go in there before the chuck fouled the cam housing. It really needs an extra-long drill bit to do the job properly. I got away with it, but more by luck than judgement!