#5 Heads
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Joined: Apr 2010
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From: MN
#5 Heads
A friend of mine is working on some #5 heads and was wondering how deep he could cut the valve pockets? Anyone have some experience with this? Also if anyone had a junk #5 head he would be interested in buying it to test how deep he could go.
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Joined: Mar 2008
Posts: 1,012
From: Phx, AZ
The valve pockets?
Technically speaking, when you say valve pockets, I think of pockets cut into pistons for clearing high lift long duration camshafts.
Is he looking to increase the valve size in the heads?
That would be the chambers.
Are you looking at porting the bowls?
From the port on out, you have port, bowl, seat, then chamber.
If he is looking at sinking the valves into the heads, that would be counter-productive, only resulting in a power loss. This is due to compression loss, and reduced flow from worsening seat location. You want to keep the valve as high in the chamber as possible.
If he is looking at increasing valve size, a 2.07" intake will easily fit, but to go larger (like 2.125") you really need to unshroud the chamber wall, requiring precision cuts. This will also require cc'ing the head, equalizing, and milling to final size.
Please convey exactly what he is trying to attempt, and for what reason. That way you will be able to get an accurate response for what he is trying to do. Everything has been done before, at least once, by someone on the boards.
Jim
Technically speaking, when you say valve pockets, I think of pockets cut into pistons for clearing high lift long duration camshafts.
Is he looking to increase the valve size in the heads?
That would be the chambers.
Are you looking at porting the bowls?
From the port on out, you have port, bowl, seat, then chamber.
If he is looking at sinking the valves into the heads, that would be counter-productive, only resulting in a power loss. This is due to compression loss, and reduced flow from worsening seat location. You want to keep the valve as high in the chamber as possible.
If he is looking at increasing valve size, a 2.07" intake will easily fit, but to go larger (like 2.125") you really need to unshroud the chamber wall, requiring precision cuts. This will also require cc'ing the head, equalizing, and milling to final size.
Please convey exactly what he is trying to attempt, and for what reason. That way you will be able to get an accurate response for what he is trying to do. Everything has been done before, at least once, by someone on the boards.
Jim
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