[Healeys] Manifold bolts

[Mark Donaldson]

Listers,

 

I have a question about the four bolts that secure the intake manifold to
the exhaust manifolds on our 6-cylinders.

Over the 60 years the threads between the aluminium (note correct spelling)
and the cast iron have been sacrificed, rendering the bolts unreliable.

The parts manual tells us they are: HBZ 056  -  3 ¼” x 5/16” with the end
thread 1” long.

 

Though an unusual bolt, I think I can source them here in NZ.

 

My question is:  What is the thread?   UNF or BSF

 

TIA

 

Mark

Ardmore

NZ 

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