Porting Big Block Heads

So, from what I’m reading (should have known Vizard was involved...he just loves the 30 degree seat) they went to the 2.14 valve and used a 30 degree seat, but didn’t use the 2.14 and a 45 degree seat to compare the 30 and 45 with the same valve size. That makes ZERO sense, unless I missed something.

I’ll say it again...even in Vizard’s porting book he points out how much pressure drop there is at low lifts...as high a 200 inches! So how does testing a port, at 28 inches and .025 prove anything? The case can be made increasing the low lift numbers in that range, when the exhaust valve is still off the seat and the header is pulling on the port all you are doing is pulling the new air/fuel charge right out of the exhaust port.


That’s how you end up with lean reading spark plugs, and dirty, wet exhaust ports.

Also, back cutting looks awesome on the flow bench, but isn’t always the cool deal in real life.