what is the difference between an extrude honed and a ported exhaust manifold besides a lot of
12-20-2001, 08:40 AM
#15
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Extrude honing is a very flexible process ...
... depending on how much time and $$$ you want to invest, you can smooth, enlarge, and/or port match.
On aluminum intake manifolds, I've gotten good results by extrude honing larger ID runners (which also polishes the runners internals) while at the same time port matching the exits to the head; but ... I've got even better results by hand porting the manifold first and then extrude honing with port matching.
With heads, I've always hand ported first to get the optimum shape of the runners and bowl above the valves, and then followed this with extrude honing to polish only with minimal metal removal.
On aluminum intake manifolds, I've gotten good results by extrude honing larger ID runners (which also polishes the runners internals) while at the same time port matching the exits to the head; but ... I've got even better results by hand porting the manifold first and then extrude honing with port matching.
With heads, I've always hand ported first to get the optimum shape of the runners and bowl above the valves, and then followed this with extrude honing to polish only with minimal metal removal.
12-20-2001, 11:52 AM
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Not necesssary with a fuel injected motor ...
..., the fuel is added just before the valves; but I'm suspicious of roughness being desirable even with a carb.
BTW, I have a photograph of a BMW Williams Formula 1 head looking up past the combustion chamber thru the intake and exhaust ports. The polish of the runners looks even better than that from extrusion honing.
BTW, I have a photograph of a BMW Williams Formula 1 head looking up past the combustion chamber thru the intake and exhaust ports. The polish of the runners looks even better than that from extrusion honing.
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