400 head porting

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May 4, 2020 | 10:23 PM

F-250 WARHORSE

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Cargo Master

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From: starship enterprise

400 head porting

I have severalsets of these heads (d5aea2a) and I have some exhaust restriction in my current 400 and I would like to help that out by improving flow on a set of these heads. I tore a set down on the benchand I feel that the boss around the guide could be the biggest benefit. There is definetely water all the way around the guide, anyone do this and figure about how much you could remove to smooth out that turn? 1/16? probably.

May 5, 2020 | 05:24 AM

BrutalBronco

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Profiling the valve guides ranks up there with adjusting the air bleeds on a race carburetor. There's plenty more efficiency to gain from subtly contouring the short turn, opening up the throat to complement the valve diameter, and unshrouding the valve with respect to the combustion chamber. I'm a fan of leaving plenty of meat around the valve guide to keep it located.

May 5, 2020 | 07:57 AM

F-250 WARHORSE

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From: starship enterprise

OK I thought that was the short turn... so what would be considered the short turn? the floor or the ceiling?

May 6, 2020 | 05:10 AM

BrutalBronco

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The short turn is the opposite side of the port from the valve guide.

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May 7, 2020 | 02:08 PM

mark a.

Lead Driver

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Short turns can be very sensitive and too much grinding on them can ruin a port. If you don't have a flow bench the best thing to do is just blend them in without changing their contour.