Re: porting a SPICA manifold

[Obadiah Fayth <fayth@xxxxxxx>]

I have started porting a 2.0l head, but haven't got to the manifold yet so
I can't say how mine fits up for comparison. I was reading a book on
porting that says on the exhaust side you should leave the diameter of the
runners 2-3mm smaller than the inner-diameter of the header in order to
create a one way restriction to improve scavanging.

My question is why would this NOT be worth doing on the intake side of
things? Why not match the intake ports and then grind the runners in the
head until they are 2mm larger in diameter? The 2mm difference only has to
extend 1" into the head and there is enough metal there so we don't have to
worry about the water jacket... Would it screw with the resonance? There
must be a reason they don't do this....

- -Obie

Tacoma, Washington
'78 Alfetta GT
'83 GTV6
'91 Subaru LS AWD

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