Speedmaster head hypothetical

[Earlie A]

Single blade cutters. The throat is now epoxy which does not hold an edge as well as the steel would.

Just curious. Why do you pick out the 50 deg seats as being bad at low lift. The 45 deg seats should be better than the 50 at low lift.

And a smaller throat will help low lift flow on a 50 deg seat. A larger throat (theoretically) helps high lift flow.

 

[Newbomb Turk]

Single blade cutters. The throat is now epoxy which does not hold an edge as well as the steel would.

Just curious. Why do you pick out the 50 deg seats as being bad at low lift. The 45 deg seats should be better than the 50 at low lift.

And a smaller throat will help low lift flow on a 50 deg seat. A larger throat helps high lift flow.

I know there’s epoxy in the bowls so you do have to deal with that.

You are making my point. The curtain area is smaller with a 50 degree seat. So you are shrinking the bowls (or a better way to say it is keeping the bowls smaller as a percentage of the valve size) so when I see gains in low and mid lifts I know someone is porting for flow numbers and not necessarily power.

On the exhaust side the port will keep flowing more the bigger you make it. That doesn’t mean it will make more power. In fact it probably won’t if the port is big and noisy.

I was lucky. The guy who told me about these steeper than 50 degree seats was pretty sharp.

Also in one of Dan Terrell’s books he covered steeper than 45 degree seats. There is some good stuff in that book but I can’t think of the name of it right now. Maybe it’s horse power secrets or something like that.

I guess I’d want to know what the sound differences are between the two valve jobs as well because that says a lot too.

Like I said, your ports from .350 on are not backing up. That’s critical. If they flatten out that’s ok, but when the curve breaks over and never comes back you know the power will be off.

 

[Earlie A]

I know there’s epoxy in the bowls so you do have to deal with that.

You are making my point. The curtain area is smaller with a 50 degree seat. So you are shrinking the bowls (or a better way to say it is keeping the bowls smaller as a percentage of the valve size) so when I see gains in low and mid lifts I know someone is porting for flow numbers and not necessarily power.

On the exhaust side the port will keep flowing more the bigger you make it. That doesn’t mean it will make more power. In fact it probably won’t if the port is big and noisy.

I was lucky. The guy who told me about these steeper than 50 degree seats was pretty sharp.

Also in one of Dan Terrell’s books he covered steeper than 45 degree seats. There is some good stuff in that book but I can’t think of the name of it right now. Maybe it’s horse power secrets or something like that.

I guess I’d want to know what the sound differences are between the two valve jobs as well because that says a lot too.

Like I said, your ports from .350 on are not backing up. That’s critical. If they flatten out that’s ok, but when the curve breaks over and never comes back you know the power will be off.

The book is Horsepower Chain.

45 deg seats have more curtain area at low lift than 50 degree seats and should always outflow the 50s at 0.050", 0.100" and usually 0.150". A tighter throat 'may' choke off 0.050" flow a little but it will help 0.100" and 0.150" flow because it helps the high speed air navigate the turn around the seat and past the valve. That's been my experience anyway.

 

[Newbomb Turk]

The book is Horsepower Chain.

45 deg seats have more curtain area at low lift than 50 degree seats and should always outflow the 50s at 0.050", 0.100" and usually 0.150". A tighter throat 'may' choke off 0.050" flow a little but it will help 0.100" and 0.150" flow because it helps the high speed air navigate the turn around the seat and past the valve. That's been my experience anyway.

Yeah I have that book too, but that’s not the one I’m talking about.

When I’m done in the shop today I’ll dig it out and post the title.

The book is Horsepower Chain.

45 deg seats have more curtain area at low lift than 50 degree seats and should always outflow the 50s at 0.050", 0.100" and usually 0.150". A tighter throat 'may' choke off 0.050" flow a little but it will help 0.100" and 0.150" flow because it helps the high speed air navigate the turn around the seat and past the valve. That's been my experience anyway.

Again, this is why I advocate for using test pressures other than 28 inches.

Plus, unless the numbers are absurdly low or the low lift numbers are **** because the valve job is garbage I don’t get too excited what’s happening at those low lifts.

It’s hard to explain in typing. That’s why I’m not sure you understood my comment about top cutting the valve.

It changes the shape of the flow around the valve and it does work. The issue becomes what happens when the flow is going backwards and we all should know it does.

That’s a case where more flow made less power.

There are some really good threads on speedtalk but finding them is next to impossible. I can’t think of the guys name but he has been doing 50 degree stuff at least as long as I have.

The **** was flying fast and hot when he said he used it on his .480 lift, tow rig heads.

There are some who claim if you don’t have .*** lift them don’t do a 50 or steeper.

I haven’t seen that matter. Neither did the other guy on ST. But guys hear a rule of thumb and marry it.

I think you are to the point where you need to pick your port and do a set of heads and get them on the dyno. Then to the track.

 

[Earlie A]

Yeah I have that book too, but that’s not the one I’m talking about.

When I’m done in the shop today I’ll dig it out and post the title.



Again, this is why I advocate for using test pressures other than 28 inches.

Plus, unless the numbers are absurdly low or the low lift numbers are **** because the valve job is garbage I don’t get too excited what’s happening at those low lifts.

It’s hard to explain in typing. That’s why I’m not sure you understood my comment about top cutting the valve.

It changes the shape of the flow around the valve and it does work. The issue becomes what happens when the flow is going backwards and we all should know it does.

That’s a case where more flow made less power.

There are some really good threads on speedtalk but finding them is next to impossible. I can’t think of the guys name but he has been doing 50 degree stuff at least as long as I have.

The **** was flying fast and hot when he said he used it on his .480 lift, tow rig heads.

There are some who claim if you don’t have .*** lift them don’t do a 50 or steeper.

I haven’t seen that matter. Neither did the other guy on ST. But guys hear a rule of thumb and marry it.

I think you are to the point where you need to pick your port and do a set of heads and get them on the dyno. Then to the track.

Thanks. Now back to the original question.

Of the two curves and with the specs given, is there enough information to feel confident about which one makes more power or runs better down the track? Or is the answer - there is no way to know?

 

[Newbomb Turk]

Thanks. Now back to the original question.

Of the two curves and with the specs given, is there enough information to feel confident about which one makes more power or runs better down the track? Or is the answer - there is no way to know?

The book is Secrets of a 740 HP Winston Cup engine.

Not a lot in there but a couple of important things.

I would have picked the port with the 50 degree seats regardless of what the flow bench said.

I still say that. Unless you totally kill the 50 I say it always makes more power.

It’s about the shape.

 

[polyjohn]

The 50 degree seat sounds like a winner for a SM head, but.

30 degree seats were always the Ford's killer combo and I have used them on 906 and J heads myself.
Without a flow bench I have no idea if the 30 degree seat is better or worse than a 45?

'Back the day' pushrod pinch, on the W2's were opened up to a rectangular port for max flow.
Dulcich did the same with his Eddy heads and PBR said they were JUNK as cast.

''Horses for Courses'' as we say, as long as folks differ in opinions there will always be healthy discussions.
Keep up the good work all you Flow Guru's and us Non-benchers (Muggles) look on in awe.

 

[Earlie A]

The 50 degree seat sounds like a winner for a SM head, but.

30 degree seats were always the Ford's killer combo and I have used them on 906 and J heads myself.
Without a flow bench I have no idea if the 30 degree seat is better or worse than a 45?

'Back the day' pushrod pinch, on the W2's were opened up to a rectangular port for max flow.
Dulcich did the same with his Eddy heads and PBR said they were JUNK as cast.

''Horses for Courses'' as we say, as long as folks differ in opinions there will always be healthy discussions.
Keep up the good work all you Flow Guru's and us Non-benchers (Muggles) look on in awe.

I am not sold on the 50 deg seat over the 45. I like the IDEA of the 50 more than the 45 for this chamber, but I'm not sure it's the way to go. I've spent more time testing with a 50 than a 45 because that's just where the seat ends up. I usually cut a 45 valve job first then at some point I start wondering how the 50 deg would perform. It's easy to turn a 45 valve job into a 50, but not the other way around. To convert a 50 to a 45 the throat/seat/chamber has to be epoxied up and re-shaped. That's a big deal, so I stay with the 50 deg seat for quite a while.

I have never tried a 30 deg seat. If it were the way to go there would be many people using it. It is almost never used. That's a big clue. A 30 deg valve job will give incredible low lift flow. After that I suspect it would fall on it's face. That is opposite of what is needed. Why make the air turn 15-20 degrees more than is needed? Air doesn't want to turn.

 

[Newbomb Turk]

I am not sold on the 50 deg seat over the 45. I like the IDEA of the 50 more than the 45 for this chamber, but I'm not sure it's the way to go. I've spent more time testing with a 50 than a 45 because that's just where the seat ends up. I usually cut a 45 valve job first then at some point I start wondering how the 50 deg would perform. It's easy to turn a 45 valve job into a 50, but not the other way around. To convert a 50 to a 45 the throat/seat/chamber has to be epoxied up and re-shaped. That's a big deal, so I stay with the 50 deg seat for quite a while.

I have never tried a 30 deg seat. If it were the way to go there would be many people using it. It is almost never used. That's a big clue. A 30 deg valve job will give incredible low lift flow. After that I suspect it would fall on it's face. That is opposite of what is needed. Why make the air turn 15-20 degrees more than is needed? Air doesn't want to turn.

You won’t be sold in the 50 until you start you g to the dyno and the track.

 

[Cuda416]

I am not sold on the 50 deg seat over the 45. I like the IDEA of the 50 more than the 45 for this chamber, but I'm not sure it's the way to go. I've spent more time testing with a 50 than a 45 because that's just where the seat ends up. I usually cut a 45 valve job first then at some point I start wondering how the 50 deg would perform. It's easy to turn a 45 valve job into a 50, but not the other way around. To convert a 50 to a 45 the throat/seat/chamber has to be epoxied up and re-shaped. That's a big deal, so I stay with the 50 deg seat for quite a while.

I have never tried a 30 deg seat. If it were the way to go there would be many people using it. It is almost never used. That's a big clue. A 30 deg valve job will give incredible low lift flow. After that I suspect it would fall on it's face. That is opposite of what is needed. Why make the air turn 15-20 degrees more than is needed? Air doesn't want to turn.

First I'll preface this as I usually do and say wrt porting etc I am probably the slow guy in the room.

Been watching a lot of Darin Morgan talks lately and as I recall in one, he states changing the seat angle can be very advantageous depending on the shape of the bowl and how the A/F mix moves out of it, past the valve and how that venturi is built up. The particular segment also mentioned how critical not going over a 15 deg change in the angles etc. He also talked about how changing the angle can be used as a "tuning" point which of course had to be checked on the track.

I'd like to add that I find these threads fascinating and hope this and other threads continue and more begin. Good stuff.

 

[Earlie A]

First I'll preface this as I usually do and say wrt porting etc I am probably the slow guy in the room.

Been watching a lot of Darin Morgan talks lately and as I recall in one, he states changing the seat angle can be very advantageous depending on the shape of the bowl and how the A/F mix moves out of it, past the valve and how that venturi is built up. The particular segment also mentioned how critical not going over a 15 deg change in the angles etc. He also talked about how changing the angle can be used as a "tuning" point which of course had to be checked on the track.

I'd like to add that I find these threads fascinating and hope this and other threads continue and more begin. Good stuff.

Thanks for contributing and participating. Morgan is definitely one of the modern gurus of this stuff. I watch everything I can where he's involved. You may already know but he is cranking up some kind of pay per view program with Drag Boss Garage on Youtube.

Agree with you on the valve and seat angle stuff. It is amazing to me how just a few thousandths of an inch can make 10 cfm flow difference and can stabilize or destabilize a port. I've made a 2.5 deg change in a back angle on a valve and changed the flow curve pretty dramatically. It just tickles my innards.

 

[273]

Thanks for contributing and participating. Morgan is definitely one of the modern gurus of this stuff. I watch everything I can where he's involved. You may already know but he is cranking up some kind of pay per view program with Drag Boss Garage on Youtube.

Agree with you on the valve and seat angle stuff. It is amazing to me how just a few thousandths of an inch can make 10 cfm flow difference and can stabilize or destabilize a port. I've made a 2.5 deg change in a back angle on a valve and changed the flow curve pretty dramatically. It just tickles my innards.

The problem with Drag Boss Garage is the host, his question always kill the flow, they need a host that can ask decent question, luckily Darin has no problem talking.

 

[Earlie A]

Case in point. Look at the difference that going from a 35 degree backcut to a 32.5 degree backcut on a 2.08 valve with 50 deg seat made. 10 cfm negative in part of the curve to 8 cfm positive. I haven't drawn it out, but I know this change is only a few thousandths of an inch.

What I haven't done yet is try to figure out why it changes so much. This is where drawing things out on the computer helps me. For example, consider the 0.200" lift position. That can be drawn out and the air flow through the curtain visualized. On the computer you can blow things up to a much larger scale and look at flow patterns. It also helps to take the head off the flow bench, open the valve to 0.200" and look at the curtain area from all directions. There is something to be learned from this one test alone. That learning will unlock some other understanding.

 

[Cuda416]

Thanks for contributing and participating. Morgan is definitely one of the modern gurus of this stuff. I watch everything I can where he's involved. You may already know but he is cranking up some kind of pay per view program with Drag Boss Garage on Youtube.

Agree with you on the valve and seat angle stuff. It is amazing to me how just a few thousandths of an inch can make 10 cfm flow difference and can stabilize or destabilize a port. I've made a 2.5 deg change in a back angle on a valve and changed the flow curve pretty dramatically. It just tickles my innards.

I'm just glad to be able to follow along. I am aware of his ppv plan, looking forward to it.

On the CFM thing though, it's eye opening, when people like he, and others around here, emphasize higher flow doesn't always win races. Like what has been said around here, flow benches lie, or as Darin puts it, they allow us to lie to ourselves. Case in point, it talks about the bowl/runner/csa relationship and bowls being sized incorrectly. He was quick to point out you can put a larger valve in, reshape the bowl and get the flow where you think it should be, but the velocity goes way down etc.

What I am leaning (and wish I had a bench/time to test things) is the balancing act between stuff Terrel talks about and what I am learning about here.

Again, it's all very fascinating and I generally try to keep quiet in my little corner but once in a while I'm going to chime in, and hopefully get some nuance I am not clear on straightened out.

Thanks again

Carry on Sir.

 

[Cuda416]

I'm going to bet when you draw it out and can see the relationship between the valve surface and seat/transition and how that small change altered the venturi, you'll have an aha moment.

It really shouldn't come as a surprise, even though it does, how minute changes alter everything. I mean, think about it. What happens when you put your hand in a 300 fps air stream and turn it slightly. I realize it's not the same thing but the point being we're talking about some really fast moving air and fuel being carried by that air. The things you are showing/discovering are the tip of the ice burg and I'm digesting as much as I can.

 

[Newbomb Turk]

Case in point. Look at the difference that going from a 35 degree backcut to a 32.5 degree backcut on a 2.08 valve with 50 deg seat made. 10 cfm negative in part of the curve to 8 cfm positive. I haven't drawn it out, but I know this change is only a few thousandths of an inch.

What I haven't done yet is try to figure out why it changes so much. This is where drawing things out on the computer helps me. For example, consider the 0.200" lift position. That can be drawn out and the air flow through the curtain visualized. On the computer you can blow things up to a much larger scale and look at flow patterns. It also helps to take the head off the flow bench, open the valve to 0.200" and look at the curtain area from all directions. There is something to be learned from this one test alone. That learning will unlock some other understanding.

View attachment 1716337523

View attachment 1716337524

As a side note, the 50 degree cutters I use show the best numbers with a 30 degree back cut.

I know that flies on the face of conventional wisdom but that’s what it likes. Also the under head radius and the angle affect what back cut it likes.

On a set of custom valves I had Donovan make for me the BC hurt flow everywhere. So I used them without the BC.

It’s like Morgan says in that you are tuning the valve job up with the angles below and above the seat angle.

I know the cutter I use (for the intake side, the exhaust is a radius) has two wide bottom cuts. I forget the angles. If you start taking too much out of the bottom cuts the port starts getting a bit chaotic around .25 l/d.

 

[Earlie A]

I'm going to bet when you draw it out and can see the relationship between the valve surface and seat/transition and how that small change altered the venturi, you'll have an aha moment.

It really shouldn't come as a surprise, even though it does, how minute changes alter everything. I mean, think about it. What happens when you put your hand in a 300 fps air stream and turn it slightly. I realize it's not the same thing but the point being we're talking about some really fast moving air and fuel being carried by that air. The things you are showing/discovering are the tip of the ice burg and I'm digesting as much as I can.

You are correct. 300 fps is seriously fast air speed. The length of a football field in 1 second. And choke velocity in the port is more than double that speed.

Stick the hand out the window of a car moving 70 mph. Thats only 103 fps.

 

[Cuda416]

Morgin also emphisiezes the whole thing begins with the cylinder bore, then the valve size, then the area 1 inch before and after the valve in both directions, then the rest.

This leads me to the question of bowl wall angle below the throat. I'm sure it's been answered but how is the angle of the wall determined for the bowl wall and is there a "tuning" method for it?

The reason I bring this up here is that It's been said the bowl in the SM heads is slightly large for the valve if I recall correctly.

 

[273]

You got enough flow technically to make 700+ hp max effort or 550-650 hp decently built healthy street strip engine (don't mean it will) so to me the issue ain't air flow, sure another 10-20+ would be nice but you got more than enough air flow to make the power most would want from those heads. To me the question is does it have the velocities and shape to make it ?

 

[Earlie A]

how is the angle of the wall determined for the bowl wall and is there a "tuning" method for it?

All I can say here is trial and error. Bowls are just as complicated as short turns. Too little area and it's the choke point. Too much area in the wrong place and the air separates which causes other problems. The valve stem and valve guide are a pain to work around and get air around. The bowl also has to be designed to deal with the problems that the pushrod pinch creates. This is particularly evident on the cyl center side of the port wall and bowl. There are some crazy airflow patterns on that side.

In my experience the bowl just below the valve seat on the SM head does not need major enlargement. Depending on the size of the motor the bowl around the valve guide and the bowl at the apex may need substantial work.

Sorry to be so vague, but some of these things are hard to describe. And please read this as me sharing experiences, not giving advice. We've got Darin and a handful of other guys around here for giving advice.

 

[Earlie A]

You got enough flow technically to make 700+ hp max effort or 550-650 hp decently built healthy street strip engine (don't mean it will) so to me the issue ain't air flow, sure another 10-20+ would be nice but you got more than enough air flow to make the power most would want from those heads. To me the question is does it have the velocities and shape to make it ?

I agree. Air flow is not the point. Learning is. As you mentioned a few days ago, the learning will eventually have to move from the bench to the dyno or the track. Just not yet.

 

[Cuda416]

All I can say here is trial and error. Bowls are just as complicated as short turns. Too little area and it's the choke point. Too much area in the wrong place and the air separates which causes other problems. The valve stem and valve guide are a pain to work around and get air around. The bowl also has to be designed to deal with the problems that the pushrod pinch creates. This is particularly evident on the cyl center side of the port wall and bowl. There are some crazy airflow patterns on that side.

In my experience the bowl just below the valve seat on the SM head does not need major enlargement. Depending on the size of the motor the bowl around the valve guide and the bowl at the apex may need substantial work.

Sorry to be so vague, but some of these things are hard to describe. And please read this as me sharing experiences, not giving advice. We've got Darin and a handful of other guys around here for giving advice.

Fair enough, thanks for your thoughts on this. Wasn't trying to sidetrack anything but I seem to be heading that way so I'll pull back and enjoy the show for now.

 

[Earlie A]

Fair enough, thanks for your thoughts on this. Wasn't trying to sidetrack anything but I seem to be heading that way so I'll pull back and enjoy the show for now.

Didn't view it as a sidetrack. I appreciate the questions and I'll answer what I can. I just may not be the right one to ask and I sure don't want to give any more incorrect answers than I already do.

 

[273]

I agree. Air flow is not the point. Learning is. As you mentioned a few days ago, the learning will eventually have to move from the bench to the dyno or the track. Just not yet.

Did you see NC Engine Builder was gonna try do a dyno mopar head shootout sometime over the winter (I think) on a 408/416 people are free to lend a set of heads they want tried out, might be an opportunity to try out your work.

Cylinder head dyno shoot out

 

[Earlie A]

Did you see NC Engine Builder was gonna try do a dyno mopar head shootout sometime over the winter (I think) on a 408/416 people are free to lend a set of heads they want tried out, might be an opportunity to try out your work.

I've been talking to him a little. We'll see how it all develops. I think he'll do a good job with it.