-Vortec Heads Max Lift-


How to make Vortec heads perform; the cheap and easy method for high lift cams

Tried and true.
Vortec heads come in three basic styles, two with 64cc chambers and one with 58cc chambers. The 58cc heads are 305 heads with slightly different ports than the 350 Vortec heads and flow dramatically less, around that of a 461 "Double Hump" or "Camel Back" head.
Of the two 64cc Vortec styles the 064 Vortec castings are the ones to have for performance but the HD 906 Vortec castings will work just the same with some port on the exhaust side and max lift modifications. They have a HD exhaust seat that impeads flow. These are very soft heads so grind slowly and delibertly being careful not to knick the seats themselves.
Vortec heads max liftVortec heads max lift
Vortec 064 Vortec heads outflow GM Aluminum heads and equal Edebrock Performer RPM heads at .500" lift due to the raised runners GM has designed into these superb heads. The problem with performance applications is not flow as with most heads, it's max lift as you may well know. Machine work can be costly and by the time machine work is paid for to allow a .510" lift cam a nice set of Aluminum heads could be purchased. Vortec Heads Max Lift and flow

The cause of this lift limitation is that the retainer comes into contact with the valve seal which is 1/10 of an inch tall{.100"}.The solution is to remove the factory posi lock valve seal and replace with a 86 Daytona 2.2l turbo umbrealla style valve seal. This allows for a max clearance of .550" lift and a safe .520" lift cam to be installed. As always the heads should be mocked up and clearances checked before install.
The other problem is that the valve guide "stub" is fatter than previous heads and a standard Valve Spring will not fit because of the inner retainer. The cheap and easy method is to run a "Z28" or "Z28 +.100" high lift valve spring {+.100" handles 550" lift and can be used on 490 or less roller cams in this application} with the inner dampner removed.

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