Decisions, decisions... square or oval port for 489?
03-30-2011, 04:23 PM
#1
Decisions, decisions... square or oval port for 489?
I am down to deciding which head to run on a Gen VI based 489. I have a set of stock 781 oval castings that need guides, and a set of 088 Gen VI rectangle port castings that have good guides but need to go up to 2.25 intakes because the 2.19's were a little sunken in. The 088's already have the hardened exhaust seat inserts.
I spend most of my time running between 3000 - 3800 RPM, with an occasional shakedown up to 5500 or so. Based on that, the oval's would seem the logical choice, however:
Total to get the 088's where they need to be will run about $375 in machine shop labor. Fixing up the 781's, including guides, cutting for larger valves, etc., will run close to $600 in labor.
Will I really see that much of a difference in midrange power with the ovals over the rectangles? Has anyone run both on a 489/496/502?
FWIW, I found a pretty good link that lists flow figures from a BUNCH of cylinder heads, from small and BB chevy to almost everything else. Here's a link:
http://users.erols.com/srweiss/table...hevy_Big_Block
I spend most of my time running between 3000 - 3800 RPM, with an occasional shakedown up to 5500 or so. Based on that, the oval's would seem the logical choice, however:
Total to get the 088's where they need to be will run about $375 in machine shop labor. Fixing up the 781's, including guides, cutting for larger valves, etc., will run close to $600 in labor.
Will I really see that much of a difference in midrange power with the ovals over the rectangles? Has anyone run both on a 489/496/502?
FWIW, I found a pretty good link that lists flow figures from a BUNCH of cylinder heads, from small and BB chevy to almost everything else. Here's a link:
http://users.erols.com/srweiss/table...hevy_Big_Block
