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Old 04-26-2011, 06:16 PM
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Your current SCR is 8.80:1, using these values....
727.41 in the cylinder
78 in the chamber (heads always pour a little bigger than advertised
7 in the piston (assuming a perfectly flat crown with 4 reliefs. If you have those Fosdick stock Chevy pistons with the well in the middle like my photo below, then yeah, you're probably at 8.5 or so because I think they will pour 12 or 13. There is little or no flat area on the crown of those to generate squish, just that narrow ring of material above the ring package.
5.01 in the piston deck height
3.24 in the gasket.

Changing to a 12407 or 12410 or 12410-01 or 12410-02 with 64cc chambers (call 'em 66 for figuring the SCR), will net you 9.95:1 SCR and ruin the chance to use a short street cam. Moving to the standard Pro Torker 12402 or 12403 with the 67cc chamber (call 'em 69 for figuring the SCR) will net you 9.63:1 and will still preclude the use of a short street cam.

I really like the GM Vortec model of head that these guys produce, but you can only get them in 64cc chambers. Moving over to the Pro Torker, you can get 76cc chambers as well.

BARE HEADS

GM VORTEC - PRO TORKER™ CYLINDER HEADS, CAST IRON
#12407 Pro Torker™ 23º GM Vortec, 170cc, 64cc, Straight plugs, 1.940" Stock Length intake valves, 1.500" Stock Length exhaust valves, 327-350c.i.

GM VORTEC - PRO TORKER™ CYLINDER HEADS, CAST IRON
#12410* Pro Torker™ 23º GM Vortec, 170cc, 64cc, Straight plugs, 2.020" + .100" Long intake valves, 1.600" + .100" Long exhaust valves, 327-383c.i.

ASSEMBLED HEADS

GM VORTEC - PRO TORKER™ CYLINDER HEADS, CAST IRON
#12410-01 Cast Iron, assembled, 170cc intake runner volume, 64cc combustion chamber volume, Straight plugs, 2.020" intake valves, 1.600" exhaust valves, Flat Tappet springs installed, 0.560" max valve lift.

GM VORTEC - PRO TORKER™ CYLINDER HEADS, CAST IRON
#12410-02 Cast Iron, assembled, 170cc intake runner volume, 64cc combustion chamber volume, Straight plugs, 2.020" intake valves, 1.600" exhaust valves, Hyd. Roller springs installed, 0.600" max valve lift.

Dual bolt pattern (4 and 6-bolt) allows
compatibility with both early-style SBC
and GM Vortec intake manifolds.

BARE HEADS

PRO TORKER™ 23° EARLY-STYLE SBC CYLINDER HEADS, CAST IRON
#12402 cast iron, bare, 170cc intake runner volume, 67cc combustion chamber volume, straight plugs, 1.94" intake valves, stock length, 1.50" exhaust valves, stock length. 327-350 cubic inches.

#12403 cast iron, bare, 170cc intake runner volume, 67cc combustion chamber volume, straight plugs, 2.02" intake valves, stock length, 1.60" exhaust valves, stock length, 327-383 cubic inches.

#12400 cast iron, bare, 170cc intake runner volume, 76cc combustion chamber volume, straight plugs, 1.94" intake valves, stock length, 1.50" exhaust valves, stock length, 327-350 cubic inches.

#12401 cast iron, bare, 170cc intake runner volume, 76cc combustion chamber volume, straight plugs, 2.02" intake valves, stock length, 1.60" exhaust valves, stock length, 327-383 cubic inches.
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Last edited by techinspector1; 04-26-2011 at 06:25 PM.
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