valve seat angle
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valve seat angle some high revving, high lift cam motors seem to reap the benefits of a 55* valve seat angle. At what rpm and what valve lift do the benefits of a 55 vs 45 degree valve seat angle come into play? Also, Is it necessary to have a copper alloy seat as opposed to a ductile iron seat when there is a 55* seat due to less surface area contact and a harder material is necessary?
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some high revving, high lift cam motors seem to reap the benefits of a 55* valve seat angle. At what rpm and what valve lift do the benefits of a 55 vs 45 degree valve seat angle come into play? Also, Is it necessary to have a copper alloy seat as opposed to a ductile iron seat when there is a 55* seat due to less surface area contact and a harder material is necessary?
Think about what a steeper valve seat angle accomplishes. Now why would you want to do that? How did you do in geometry in school?
Trying to teach you to fish....
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How is the longevity of a 55* angle seat compared to a 45* angle seat?
If I had access to a program called fluent and enough talent to draw up a schematic in that program, I would test it out to see precisely the differences in flow at relative valve lifts...
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a steeper angle accomplishes a more direct route for flow...but only at higher lift and with a little sacrifice to lower lift flow. I did very well in geometry...A...and im an engineer now, so I understand how everything works in relation, however, what I don't know is approximately at what lift does it begin to flow better than a say 45* angle and approximataly what overall peak lift would be deemed necessary to do a 55* valve seat angle?
How is the longevity of a 55* angle seat compared to a 45* angle seat?
If I had access to a program called fluent and enough talent to draw up a schematic in that program, I would test it out to see precisely the differences in flow at relative valve lifts...
How is the longevity of a 55* angle seat compared to a 45* angle seat?
If I had access to a program called fluent and enough talent to draw up a schematic in that program, I would test it out to see precisely the differences in flow at relative valve lifts...
Good luck!
Jon
If you want more information on valve seat angles, look up Gordan Blair's "Design and Simulation of 4 stroke engines".
He talks about frustrum area of the valve in relationship to opening. What you are doing with valve angles is making the frustrum area of the valve suit a certain port. A lower valve angle will have a higher initial frustrum cone but will be overcome by the port. It is vice versa on the steeper angles. I know certain people that are really good at valve jobs tend to stick with the 45 for durability and go with steeper angles for "sprint" or drag racing.
He talks about frustrum area of the valve in relationship to opening. What you are doing with valve angles is making the frustrum area of the valve suit a certain port. A lower valve angle will have a higher initial frustrum cone but will be overcome by the port. It is vice versa on the steeper angles. I know certain people that are really good at valve jobs tend to stick with the 45 for durability and go with steeper angles for "sprint" or drag racing.
I thought 30 degrees was more common.
Surface area can be the same no matter what angle you use, they cut the valve margin the same width.
But what ever you decide make sure your machine shop can do it, most "in town" shops don't like to or can't do custom valve angles.
Surface area can be the same no matter what angle you use, they cut the valve margin the same width.
But what ever you decide make sure your machine shop can do it, most "in town" shops don't like to or can't do custom valve angles.
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From: Upstate NY
"fish" was not my first choice of words.
Back OT:
Think about how the air sees the valve/valve seat area with different seat angles. That might give you some clues as to why different seat angles might be used. Remember that engine performance, especially airflow in and out, relies on a combination of many things. Expand your mind...
Back OT:
Think about how the air sees the valve/valve seat area with different seat angles. That might give you some clues as to why different seat angles might be used. Remember that engine performance, especially airflow in and out, relies on a combination of many things. Expand your mind...
give me some dimensions of parts, or if you can cad up a valve in a port send it to me.
will be a good example for the coops to run and play with.
off top of my head, stem diameter is 11/32"
and an intake is 2.02" ? exhaust is 1.6" ? for valve face diameter?
what are the dimensions for the seat, and from the seat angle of 45 deg to the valve face?
How long is the 30 deg backcut?
and how about cross sectional area of the port?
Last edited by 1 FMF; Feb 20, 2008 at 09:30 PM.
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I put some guesses in below. I was hoping I could get some real numbers, but that couldnt happen since im so freekin busy. Either way, seeing the differences with high lift numbers (over .8) would be very interesting/educational...thanks for all the help!!!
give me some dimensions of parts, or if you can cad up a valve in a port send it to me.
will be a good example for the coops to run and play with.
off top of my head, stem diameter is 11/32"
and an intake is 2.02" ? exhaust is 1.6" ? for valve face diameter? That is a good average number for both of them.
what are the dimensions for the seat, and from the seat angle of 45 deg to the valve face? The seats are generally .05 wide or so depending on application, but that is a good approximation I would say..
How long is the 30 deg backcut? I am going to guess around .075 or so?
and how about cross sectional area of the port? This could very depending on the port job a good amount, guessing 3.4 with a 2.02 intake valve i'd guess, with out a head in front of me to measure, that is just a guess, does that sound right?
will be a good example for the coops to run and play with.
off top of my head, stem diameter is 11/32"
and an intake is 2.02" ? exhaust is 1.6" ? for valve face diameter? That is a good average number for both of them.
what are the dimensions for the seat, and from the seat angle of 45 deg to the valve face? The seats are generally .05 wide or so depending on application, but that is a good approximation I would say..
How long is the 30 deg backcut? I am going to guess around .075 or so?
and how about cross sectional area of the port? This could very depending on the port job a good amount, guessing 3.4 with a 2.02 intake valve i'd guess, with out a head in front of me to measure, that is just a guess, does that sound right?
