Well I suppose I ought to do some sort of update.
Recently it became time to do something about the front and rear of the exhaust, they were both rather rusty and the exhaust was leaking from the downpipe to middle section joint where it was rather crusty-rusty. The middle section had been replaced on the 2011 holiday as the silencer there had a hole in it.
Now sometime around Dec 2011, I had bought an early downpipe to fit, but I rejected doing the job at the time on the basis that the studs would shear. So it was all put on the back burner...until now
The downpipe to manifold studs were double-nutted. On the first two studs, the outer nuts moved with some persuasion. Then upon attacking the main nuts, the studs decided to shear flush with the downpipe flange. On the last stud, the outer nut sheared the stud flush with the inner nut. I bottled it at that point and used the car for a couple more days until I brought reinforcements in....
DSCF6942.JPG by
macplaxton, on Flickr
The M10 stud and cone lock nut on the left is for a later B14 manifold where the manifold/downpipe flange points rearward. The early B14 manifolds uses M8 studs and the manifold/downpipe flange points forwards. Gaskets are different.
Armed up, the last stud was sheared off and the manifold removed from the head. (As you can see a few hoses have to be popped off the transfer pipe and the carburettor heated flange).
DSCF6949.JPG by
macplaxton, on Flickr
Notes: Manifold to downpipe flange has three M8 x 1.25 studs. The starter motor heat shield has two M8 x 1.25 studs (stainless steel, not sure if original, but maybe it was until the bean counters found out). The manifold to hot air tube/plate has three M7 x 1.00 studs holding it on. The inlet manifold is bolted to two M7 x 1.00 studs on the top of the exhaust manifold (at least these ones undo easily) The rest can/will be a pain). The manifold has a Renault part number in the casting - 77 00 597 631.
After that it was off to the shed to get the three busted studs out by welding some M10 nuts onto the remnants. This was a bit fruitless as whilst the welds were okayish, they were no match for the stuckness in the cast iron. No amount of brute force or penetrating spray stuff could move these. It needed heat and lots of it. Forget butane, more time was wasted getting something hotter.
DSCF6951.JPG by
macplaxton, on Flickr
This gas axe ,in combination with welding some nuts on the broken studs, managed to get somewhere at last.
DSCF6950.JPG by
macplaxton, on Flickr
Two out, one to go. It also made light work of shifting the other five rusty nuts.
DSCF6952.JPG by
macplaxton, on Flickr
I had to clean up the threads in the manifold/downpipe stud holes with a tap and used a die on the M8 starter heat shield threads. Left those studs where they were so I wasn't creating too much work for myself. Left the manifold to hot air tube/plate off until I feel the urge to fabricate something up to fix the rusted off corner. Used brass M8 nuts on the five M8 studs.
Mounted the inlet and exhaust manifolds back on the head and struck a problem. Despite having the car up in the air, the downpipe wouldn't come out. Checked this thread...
http://www.volvo300mania.com/forum-uk/v ... =2&t=11797 , removed the manifolds again and plucked it out through the top instead.
I had trouble getting the mid section to slide onto the end of the downpipe, so without a pipe expander, I started bashing away with a 30mm socket to try and take the pinch out. This was mildly successful, and I was able to get a gas-tight seal. However, the exhaust was now a bit far back (previously it had been too far forward in order to get a seal), but it was good enough for the meantime. It was vibrating against the tow bar though.