3 angle valve job?
Lead Driver
Joined: Mar 2004
Posts: 8,922
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If you grind a 45 deg angle for the valve to seat on you will have 2 sharp edges on the seat, one on the bottom one on the top. A 3 angle uses 2 more cuts to relieve the sharp edges. 30 top 60 bottom. This increases air flow through the valve seat.
Laughing Gas
Joined: Nov 2002
Posts: 1,198
Likes: 9
From: Fairmont
Most but not all valve seats have a 45 degree angle, when you do a 3-angle VJ, you add a 30 degree angle and a 60 degree angle hence the 3 angle VJ. Besides correcting the location of the seat it also gives more of a radius for the air to flow around. Air does not like to flow around sharp corners. A good 3-angle VJ will also consist of back cutting the valve. You would add a 30 degree cut and again getting more of a radius. Another step is a 45 degree cut on the front side of the exhaust valve. When the air is exiting the chamber and "hits" the exhaust valve, the 45 helps "route" the air around the valve head.
The new term we now use in the machining field is "multi angle" VJ. The valves are treated about the same, but the seat has a 15,30,45,60,78 degree cuts on them. We use a formed carbide cutter to cut our valve seat and it has all the angles on it. Some are just a big smooth cutter.
Hopefully this give you an idea, there are more things to do but I might have over complicated this already.
The new term we now use in the machining field is "multi angle" VJ. The valves are treated about the same, but the seat has a 15,30,45,60,78 degree cuts on them. We use a formed carbide cutter to cut our valve seat and it has all the angles on it. Some are just a big smooth cutter.
Hopefully this give you an idea, there are more things to do but I might have over complicated this already.
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