I just dropped my 300 head off to get hot tanked, brass valve guides and a 3 angle valve job. My machinist asked me what angles wanted and I haven't got a clue. I have a comp cams 260H cam and matching kit with a Clifford performance single plane intake and an edelbrock 500cfm carb. What would be the best angles to run with this combo?
three angle valve job, what angles work best?
- Thread starter ledfoote390gt
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A standard 3 angle valve job is a 30-45-60 degree cut. These are on the seat of the head. The valves are normally a 44 degree cut with a 30 degree back cut on the intake valves for a little more flow on the bottom end of rpms. It's usually not advisable to back cut the exhaust valves, since they transfer their heat buildup thru contact with the seat when closed. It is just above this post called "What a 3 angle valve job is" under Hardcore Inline Tech. It is a good example with pics of this and port areas. As a machine shop they should know this already, except the port work areas. I wish you well.
Darrell
Darrell
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As far as valve seat angle itself there are more than one possibilities.
A relatively shallow intake valve seat angle such as 30 degrees will promote high flow at LOW VALVE LIFTS. This may be desireable in a racing situation where the valve lift and/or duration is limited by stipulations in the class rules. Conversely a valve seat angle of say, 48 degrees will not begin to flow as much as the 30 degree seat does at low lifts but generally will out flow the 30 degree intake valve at VERY HIGH lifts.
Once the seat angle is determined then the secondary entry and exit angles can be established.
High end and high tech engines have largely gone to radiused valve seats. You can approximate this optimal radius seat after you do a typical 3-angle seat job by taking a half-round jewelers file and blending the entry angle and exhaust angle to the throat and chamber, respectively.
A relatively shallow intake valve seat angle such as 30 degrees will promote high flow at LOW VALVE LIFTS. This may be desireable in a racing situation where the valve lift and/or duration is limited by stipulations in the class rules. Conversely a valve seat angle of say, 48 degrees will not begin to flow as much as the 30 degree seat does at low lifts but generally will out flow the 30 degree intake valve at VERY HIGH lifts.
Once the seat angle is determined then the secondary entry and exit angles can be established.
High end and high tech engines have largely gone to radiused valve seats. You can approximate this optimal radius seat after you do a typical 3-angle seat job by taking a half-round jewelers file and blending the entry angle and exhaust angle to the throat and chamber, respectively.
Thanks guys. He did kow the standard angles and has all the tooling but he hadn't ever done a 300 head and asked me if I knew what worked best for these engines he has bits where he can do 10 different combinations. He is very interested in doing it as it is anythin different than a vtec Honda, haha
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Just go with a 30/45/60.
I like to grind in 1/2 degree of interference and then hand lap it out.
I like to grind in 1/2 degree of interference and then hand lap it out.
