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Old 06-24-2010, 11:50 AM
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F-BIRD'88 F-BIRD'88 is offline
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Everything you posted about porting the 305 heads (and other stock SBC heads in general) is incorrect.
Do not deshoud out to the cylinder wall. The air does not flow in that direction.
It flows toward the spark plug. Flow a garden hose thru the intake port and watch the water flow pattern thru the port into the chamber.
If you only "pocket port" these heads you will get minimum results.
The meat and potatoes (air flow gain) is deep in the port. The whole port.
On a 305 cid motor you can keep the stock 1.84x 1.50 valves or cut down some old usable/regrindable 1.94 x 1.60 valves to a 1.90" x 1.55" custom valve size on a lathe and regrind the valve seat. Or use a 1.94x 1.50 valve pair. Irreduardless only minumum deshrouding is nessessary. The area between the valve edge and cylinder wall zone is not a critical area.
If the new larger valve is .050" bigger radius you only need to clearance deshoud by .050" (or less) around the valve.

You need high speed carbide porting cutting burrs, 1 with a 6" shaft to get deep in the intake port around the guide boss. The sanding rolls are for finishing. (mostly eye wash)

Do the whole port including the valves guide boss area.
Use a felpro 1205 gasket as a guide. Raise the port roof don't lower the floor but recontour the short side radius.

The 110LSA xe cams are not compatable with the stock TPI computer.
Buy a EFI computer friendly XE cam on 113 or 114LSA.
raise the cr 10:1 if you want a larger than stock cam. (shave the heads, thin head gasket)
You will need high 4.10 rear gears and a high stall 3000-3500-4000 converter to get a 305 going. (especially with a big cam.)

Use long tune headers, 2.5" Y 'ed into 1 big 3" exhaust. Use two small case 2.5" cats.

Search my old posts for pics of the desired finished 305 head port and bowl contour. Pocket porting is not going to cut it.

Last edited by F-BIRD'88; 06-24-2010 at 12:00 PM.
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