Welding flange plate to head - what plate material is best?

[addo]

Considering the idea of welding a flange to a log-style head for the attachment of a manifold, which is the better material to make the flange out of - cast iron, or steel?

How critical is this over thousands of heat cycles?

Thanks, Adam.

 

[MustangSix]

Steel is much easier to work with. The coefficient of expansion should be close enough that it will never be a problem.

Brazing is probably the best bet for attaching it. Brass will be strong enough, won't require enough heat to cause the cast to expand too much, and will provide some flexibility between the materials.

 

[addo]

Thanks. I was leaning towards 11/16" or so steel because of manufacture cost. But thermal cycling worried me. Furnace brazing was the general idea.

The vintage car place who weld/braze stuff have a pretty hefty minimum charge and I was thinking that three heads would probably cost the same as one for the brazing - if everything is ready to go otherwise.

 

[MustangSix]

11/16" seems very thick. Even if you wanted to thread it, 3/8" (9.5mm) would probably be more than adequate.

 

[addo]

The problem is blending runners. I want to make a faux-2V head, and the "slab" part of their flange was originally 5/8" finished. The ports start to angle and turn immediately from the manifold mounting face.

Without the constraint of needing to match an existing part, 3/8" would be plenty. It's all I need for the angle-mounted LYNX triple SU rig, for sure.