Quick head porting question
12-12-2002, 12:14 PM
#1
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Join Date: Jan 2002
Location: Denton,TX USA
Posts: 160
Quick head porting question
ALright, im proting a set of gm 441 head, as i have been for the last 4 months, and have one question about the exhuast port. Here is a crappy drawing of it, but the arrow points to the edge that i;m not sure that i need to grind down, its a fairly shapr edge, but is also part of the lowest angle of the valve job. 
12-12-2002, 10:29 PM
#2
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Join Date: Jun 2001
Location: TX
Posts: 1,211
Link doesn't work.
Yes, that should be radiused, but very lightly. Don't try to hog it out, just smooth it so it makes an easy transition to the throat. The short side radius is critical. Use a stone (it's too easy to take too much with a cutter), light pressure, and keep it moving. If you stop for even an instant, you'll create a dip. If you then try to even it out, it's downhill from there.
The short side radius is tough to see, even if you put light down the port. So I do it by feel. Your fingers are very sensitive and will quickly let you know where smoothing is needed. Change the introduction angle of the stone as you work it back and forth to get a nice radius.
Yes, that should be radiused, but very lightly. Don't try to hog it out, just smooth it so it makes an easy transition to the throat. The short side radius is critical. Use a stone (it's too easy to take too much with a cutter), light pressure, and keep it moving. If you stop for even an instant, you'll create a dip. If you then try to even it out, it's downhill from there.
The short side radius is tough to see, even if you put light down the port. So I do it by feel. Your fingers are very sensitive and will quickly let you know where smoothing is needed. Change the introduction angle of the stone as you work it back and forth to get a nice radius.
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