Competition Cylinder heads: ported vs. extrude-honed

[GO 4LO]

With the number of options for ported or extrude-honed cylinder heads steadily increasing, has anyone on the board had the opportunity to try heads from multiple companies? Just curious about the benefits of porting vs. extrude-honing, and whether the flow numbers really correspond directly to actual measured improvements in power or egt's.

Chris

 

[MCummings]

Bigger valves would help too.



I think Extrude hone would be the better way,, but what do I know?...



Merrick

 

[Reb.B]

the extrude hone that i have seen doesn't work well with cast iron. I would take all day, JUST to polishish the head. Porting is much more efficient, but extrude hone would be the icing on the cake. Extrude hone does work very well on aluminum heads though.

 

[Forrest Nearing]

extrude honing should only be done once hand porting is complete, and even then it's questionable...



extrude honing removes metal evenly... but generally you don't just want to enlarge what's already there, you want to re-shape different areas to achieve better flow... the short turn radius is a big example of this on these heads...



to get optimal flow, you must hand port... extrude honing afterwards can help, but it's questionable as to wether or not it's worth the money IMHO. it's better for stuff like exhaust manifolds or long runner intake manifolds where a die grinder can't reach and where stuff is mostly symetrical...



you'll never find a serious race engine with anything extrude honed... finding optimal flow requires hours on the flow bench and tweaking here and there.



Forrest