port work question

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Apr 23, 2008 | 08:03 PM

bigblueovalman

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Joined: Nov 2006

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port work question

I have a 1986 351 HO engine and just bought some E7TE heads from Allied Motorspots. They are completely rebuilt with five angle valve job,new guides,springs, posilock valve seals and resurfaced. I want to grind out the thermactor bump to help the flow a little more. The engine is fairly stock with a Comp Cams Xtreme 4X4 grind 262deg- 270 deg 111deg lsa.
My question is about opening the exhaust ports up to match the gaskets or not. I've been told that these heads are a high velocity head and I don't know if I should open the exhaust ports up for fear of losing the velocity of the flow or not. Also thinking of a good set of Hooker full length headers.
Whatcha think?? Bud

Apr 23, 2008 | 10:50 PM

Conanski

FTE Legend

Joined: Jun 2006

Posts: 31,930

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From: Ottawa, Ontario

What you want to do is remove the exhaust valve, grind the air injection hump flat, blend and smooth the bowl area behind the valve right up to the seat(carefully so as not to damage the valve job), and then open the port up smoothly to the gasket surface. You can almost completely ignore the floor of the port(besides smoothing obvious defects), concentrate on making the roof and walls a seemless flowing surface.

You can grind these ports right into the water jacket and still not have enough airflow for a 351, so you don't have to worry about making them too big, but don't get too crazy or you will find water, or more likely a pushrod hole.