The MGA With An Attitude
LEAKY THREADS in Cylinder Head - CH-112

On 29 May 2009, Norm in Texas wrote:
"I removed the intake/exhaust manifold studs from the head. When I did oil started to seep out of the stud holes. Is this normal or am I looking at a blown head gasket or worse"?

As far as I know, all models of Austin B-series engine heads have four of the six manifold stud holes going thorough to "T" into the head bolt holes. Oil can flow (slowly) down the head bolt from the threads and nut on top. It can then weep out (slowly) through threads on the manifold studs, resulting in smell and smoke as the oil drips onto the hot exhaust manifold. The solution is to apply a touch of thread sealant on the threads of those four manifold studs in the head.

As a side note, on rare occasion someone may install incorrect manifold studs with too much thread length on the inboard end. These can then serve as set screws bearing against the side of the head studs, then making it impossible to remove the cylinder head until the manifold studs might be removed.

Additionally on MGA cylinder heads, and likely some early MGB heads as well as other similar heads, two of the three thermostat cover stud threads go through into the water jacket. These also need a touch of thread sealant during assembly. If these are not sealed water can leak into the space around the stud causing the stud to rust (and swell), making it very difficult to remove the thermostat cover.

I can't recall right offhand, but some of the water pump bolt holes might also go through into the water jacket (and need thread sealant).

Thank you for your comments -- Send e-mail to <Barney Gaylord>
© 2009 Barney Gaylord -- Copyright and reprint information