Yes, the studs are probably corroded into the manifold.
First lots of penetrating lubricant; and give it time to penetrate.
There is a definite art to hammering things so that they will budge but without causing too much damage.
You can aim your blows much more precisely using a drift, which should generally be of a slightly softer material than the article you are whacking. I had the same trouble myself last week and an offcut of 1" aluminium round bar was my implement of choice.
A good place to start is the accessible bit of 'downpipe' at the front end. Lots of small taps with the hammer are usually a better and safer way to get things moving than hefty blows - jiggle it loose and try to alternate directions, not all the same way. Once a gap has opened up set aside the hammer and start prying with a pair of tyre levers or flattish screwdrivers; again, from both sides.
First lots of penetrating lubricant; and give it time to penetrate.
There is a definite art to hammering things so that they will budge but without causing too much damage.
You can aim your blows much more precisely using a drift, which should generally be of a slightly softer material than the article you are whacking. I had the same trouble myself last week and an offcut of 1" aluminium round bar was my implement of choice.
A good place to start is the accessible bit of 'downpipe' at the front end. Lots of small taps with the hammer are usually a better and safer way to get things moving than hefty blows - jiggle it loose and try to alternate directions, not all the same way. Once a gap has opened up set aside the hammer and start prying with a pair of tyre levers or flattish screwdrivers; again, from both sides.