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?