Fast Shafts

I've got a 427 tall deck, stroked out to a 496 CID, oval port heads with new innconnel valves/springs, a Crane 139651 cam, new pistons/rings and crank, 9.3 to 1 compression, 850 carb. Looking for guesstimates as to horsepower & Torque. Thanks!!
Bob G

Fast Shafts

Anyone? I'm hoping for 525. Hope this is realistic.

Chris Sunkin

Should be no problem. Should have a big, fat torque curve and that's more important.

Andy

We built a 496 like yours same cam but with GM rec port 990 heads with a mild port job made 510hp

Fast Shafts

Thanks!! One more question, I've got a set of Rect port Gen VI heads, will they work on a Gen IV block?? How much of a gain in power??
Thanks again.
Bob G

Andy

I have put a set of gen6 heads, called L29 Vortecs on a gen4 block. You have to use a special Felpro gasket, I cant remember the part number and drill a 3/16 hole on each cylinder deck surface. There are instructions with the gaskets. The only thing you are going to watch out for is comperssion. The L29 heads have a 105 cc combustion chamber where your ovals have 118. With my flat top pistons (9.5/1 final cr ratio) and cutting the heads for bigger valves I gained 50hp per side

Chris Sunkin

The rectangle ports will give you better top end performance with a small sacrifice in mid-range. This is due to the fact that the larger port sized cause intake flows to be a bit slower. That cam is enough to support the heads though.

Some people use an oval-port manifold on the rectangle heads as a way of hanging onto some more of that mid-range. Most of the GM rectangle iron heads benefit greatly from a little bowl work on the ports- particularly on the exhaust side. Nothing you need any particular knowledge for, just smoothing and clean-up.

What exhaust?