Thread: Noticeable difference?

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Judging by the dyno tests on ryanscarpage, the Vortecs will whip any of the OEM heads and also most of the aftermarket heads except AFR's and some twisted wedge heads. I agree with 69elko that the runners are too big on the Sportsman heads for a street-running 350. A rule of thumb for a street motor is half the cubic inches for runner volume, so the Vortecs would get the nod if it were me buying the parts. They're 64 cc chambers with 170 cc intake runners. I'd use a true flat-top piston, not the stock Chevy type with a depression in the middle and 4 valve reliefs, because you will not get a good squish with them. Chevy says the Vortecs work best with flat-tops. I'd buy the low-buck assembled heads (Chevy 12558060) and change out the springs and retainers to the Crane units under part number 10309-1. No machining required and good for valve lift of 0.575", about 0.125" better than the stock springs and retainers.

0.030"-over flat-tops will give you 10.4:1 with 0.040" gasket and zero deck. Use something like the Crower Hot Street Beast, part number 00903, grind number 278H, 112 LDA, 278*/284* advertised, 218*/226* @0.050" tappet lift, 0.462"/0.470" theoretical valve lift. Makes power from 2,000 to 5,700 with valve float at 6,200+. A 2,000 stall converter will put the icing on the cake.