The 906 Vortecs were used on the heavier duty trucks and have pressed in hardend exhaust seats which makes them more durabale and resistant to cracking. The down side is, the machining mismatch of the pressed in seats with the bowl walls. The mismatch is miminal and can be blended but these heads dont flow quite as well as the 062s. But again, the difference is very, very slight. I would use them.
, the springs have around 70#s on the seat and if you want to run much more than .450 or so of lift you'll need to up grade springs and shorten the valve guides for retainer to seal clearance.
[ 03-23-2005, 12:25 PM: Message edited by: kamero68 ]
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68 Camaro 505, TH400, 3.73, hyd roller, 049s
1/4 mile track----1.552---6.90/ 100.22---10.89/123.15
1/8 mile track----1.557---6.92/ 99.71
3500# , 2995 foot elavation