50 degree valve seats in modern hot street builds: is it finally time?

[NewbVetteGuy]

I'm almost afraid to reference the other "rule of thumb" thread, but I do want to ask: Are there any "rules of thumb" about how a cam recommendation changes with the move from a "typical" 45 degree set of valve angles to a "typical" 50-degree profile?

The other thread started looking at discharge coefficients and from this thread, we know moving to 50 degree profiles makes the discharge coefficients increase fairly significantly.

-Is there any sort of generalization that can be taken away between what's ideal for the cam for two otherwise identical motors with only the valve angles changed from a typical 45 to a typical 50? -I thought I saw some discussion that with improving discharge coefficients, the recommended LSA widened, but the other thread was just too painful to read for me to spend much time in it... -I could see you wanting to actually DECREASE the LSA with 50 degree seats to get more overlap to take advantage of the decreased reversion so I'm all sorts of confused...



Adam

In theory a 50 would make the engine see a smaller valve so the LSA would be tighter. For example Creasons EMC engine on a 45 would want a 108 to 109 but if you refigure it for a 50 it puts it in the 105 or 106 range. In theory.

That makes sense. I would've guessed that a 50 wanted the lobes closer together until I misread the other thread and got confused. Maybe I am starting to learn via osmosis on ST...


Adam

[GARY C]

I'm almost afraid to reference the other "rule of thumb" thread, but I do want to ask: Are there any "rules of thumb" about how a cam recommendation changes with the move from a "typical" 45 degree set of valve angles to a "typical" 50-degree profile?

The other thread started looking at discharge coefficients and from this thread, we know moving to 50 degree profiles makes the discharge coefficients increase fairly significantly.

-Is there any sort of generalization that can be taken away between what's ideal for the cam for two otherwise identical motors with only the valve angles changed from a typical 45 to a typical 50? -I thought I saw some discussion that with improving discharge coefficients, the recommended LSA widened, but the other thread was just too painful to read for me to spend much time in it... -I could see you wanting to actually DECREASE the LSA with 50 degree seats to get more overlap to take advantage of the decreased reversion so I'm all sorts of confused...



Adam

In theory a 50 would make the engine see a smaller valve so the LSA would be tighter. For example Creasons EMC engine on a 45 would want a 108 to 109 but if you refigure it for a 50 it puts it in the 105 or 106 range. In theory.

That makes sense. I would've guessed that a 50 wanted the lobes closer together until I misread the other thread and got confused. Maybe I am starting to learn via osmosis on ST...


Adam

For some reason no one testing valve angles are willing to test cams as well, they just change the valve angle and draw a conclusion.

[Rick360]

For some reason no one testing valve angles are willing to test cams as well, they just change the valve angle and draw a conclusion.

Said the guy who hasn't done ANY testing but has read a book with all the answers about cam selection.

Get your wallet out and YOU do the 50º valve job and cam testing so it's done right. Make sure you buy enough cams to test everything.

Rick

[Rick360]

I'm almost afraid to reference the other "rule of thumb" thread, but I do want to ask: Are there any "rules of thumb" about how a cam recommendation changes with the move from a "typical" 45 degree set of valve angles to a "typical" 50-degree profile?

The other thread started looking at discharge coefficients and from this thread, we know moving to 50 degree profiles makes the discharge coefficients increase fairly significantly.

-Is there any sort of generalization that can be taken away between what's ideal for the cam for two otherwise identical motors with only the valve angles changed from a typical 45 to a typical 50? -I thought I saw some discussion that with improving discharge coefficients, the recommended LSA widened, but the other thread was just too painful to read for me to spend much time in it... -I could see you wanting to actually DECREASE the LSA with 50 degree seats to get more overlap to take advantage of the decreased reversion so I'm all sorts of confused...



Adam

IMO the seat is altering the flow at low lifts which is on the opening and closing side which leads me to believe that the LSA reqd wouldn't change but the ideal duration would probably be a little longer with the steeper seats.

Rick

[GARY C]

For some reason no one testing valve angles are willing to test cams as well, they just change the valve angle and draw a conclusion.

Said the guy who hasn't done ANY testing but has read a book with all the answers about cam selection.

Get your wallet out and YOU do the 50º valve job and cam testing so it's done right. Make sure you buy enough cams to test everything.

Rick

You want others to accept the conclusion of your testing but I am not allowed to draw a conclusion off of someone else testing?

It is possible to study others testing and draw a conclusion without testing your self... It's done in science everyday.

One thing for sure is that if you exclude it you will never know.

BTW I am not claiming one is better than the other I am only stating that from the test I have seen none of them prove to be conclusive.

[Warp Speed]

I'm almost afraid to reference the other "rule of thumb" thread, but I do want to ask: Are there any "rules of thumb" about how a cam recommendation changes with the move from a "typical" 45 degree set of valve angles to a "typical" 50-degree profile?

The other thread started looking at discharge coefficients and from this thread, we know moving to 50 degree profiles makes the discharge coefficients increase fairly significantly.

-Is there any sort of generalization that can be taken away between what's ideal for the cam for two otherwise identical motors with only the valve angles changed from a typical 45 to a typical 50? -I thought I saw some discussion that with improving discharge coefficients, the recommended LSA widened, but the other thread was just too painful to read for me to spend much time in it... -I could see you wanting to actually DECREASE the LSA with 50 degree seats to get more overlap to take advantage of the decreased reversion so I'm all sorts of confused...



Adam

IMO the seat is altering the flow at low lifts which is on the opening and closing side which leads me to believe that the LSA reqd wouldn't change but the ideal duration would probably be a little longer with the steeper seats.

Rick

Yep, makes the cam seem smaller.......
One of the advantages.........."in theory" anyway! Hahaha

[GARY C]

I'm almost afraid to reference the other "rule of thumb" thread, but I do want to ask: Are there any "rules of thumb" about how a cam recommendation changes with the move from a "typical" 45 degree set of valve angles to a "typical" 50-degree profile?

The other thread started looking at discharge coefficients and from this thread, we know moving to 50 degree profiles makes the discharge coefficients increase fairly significantly.

-Is there any sort of generalization that can be taken away between what's ideal for the cam for two otherwise identical motors with only the valve angles changed from a typical 45 to a typical 50? -I thought I saw some discussion that with improving discharge coefficients, the recommended LSA widened, but the other thread was just too painful to read for me to spend much time in it... -I could see you wanting to actually DECREASE the LSA with 50 degree seats to get more overlap to take advantage of the decreased reversion so I'm all sorts of confused...



Adam

IMO the seat is altering the flow at low lifts which is on the opening and closing side which leads me to believe that the LSA reqd wouldn't change but the ideal duration would probably be a little longer with the steeper seats.

Rick

Yep, makes the cam seem smaller.......
One of the advantages.........."in theory" anyway! Hahaha

Smaller than what?

If the valve angle makes the engine see a different cam then wouldn't that conclude that a different cam should be part of the test?

[Warp Speed]

IMO the seat is altering the flow at low lifts which is on the opening and closing side which leads me to believe that the LSA reqd wouldn't change but the ideal duration would probably be a little longer with the steeper seats.

Rick

Yep, makes the cam seem smaller.......
One of the advantages.........."in theory" anyway! Hahaha

Smaller than what?

If the valve angle makes the engine see a different cam then wouldn't that conclude that a different cam should be part of the test?

Than what it is!
Does valve angle make the engine see the cam differently?

[GARY C]

Yep, makes the cam seem smaller.......
One of the advantages.........."in theory" anyway! Hahaha

Smaller than what?

If the valve angle makes the engine see a different cam then wouldn't that conclude that a different cam should be part of the test?

Than what it is!
Does valve angle make the engine see the cam differently?

Does it change widow area in relation to piston position?

What role does the cam play in an engine?

[Warp Speed]

Smaller than what?

If the valve angle makes the engine see a different cam then wouldn't that conclude that a different cam should be part of the test?

Than what it is!
Does valve angle make the engine see the cam differently?

Does it change widow area in relation to piston position?

What role does the cam play in an engine?

You didn't answer my question.
Explain "window area".

[Warp Speed]

You were obviously leaving out valve "seat" angle.
Yes, it helps you have your cam and eat it too!

[GARY C]

Than what it is!
Does valve angle make the engine see the cam differently?

Does it change widow area in relation to piston position?

What role does the cam play in an engine?

You didn't answer my question.
Explain "window area".

The area where you hang your curtains.

[MadBill]

If the cam was correct for the 45° seat, it would seem logical that a couple of degrees more for both IVO and IVC could be required with a 50° one (and thus no change in ICL or LSA) to compensate for the reduced low lift flow.

This would be a good investigation for someone with a recent version of Dynomation or a similar/higher level simulation software program. m ke I believe is one Speedtalker with same..

[Warp Speed]

Does it change widow area in relation to piston position?

What role does the cam play in an engine?

You didn't answer my question.
Explain "window area".

The area where you hang your curtains.

Dude, if you don't get it by now, never mind!

[GARY C]

You didn't answer my question.
Explain "window area".

The area where you hang your curtains.

Dude, if you don't get it by now, never mind!

If you conclude a partial test as conclusive I would have to say the same to you.

Should I have added that the curtain area is the area that covers the window and the terms are used interchangeably?