SBM Edelbrock/Speedmaster Head Data

[polyjohn]

On the matter of porting for all out power!

I guess most folks have seen the Dulcich Edelbrock mods and the 90hp he found!
That was going to be my plan also, but finding offset rockers is getting difficult indeed.

So what can be achieved without the Dulcich 'pushrod-pinch' mods?
500hp would be a great step forwards for a street driven 360ci.

But looking at the 305 T/A heads that were done in 1971, is 360ci too big?
Is going 408ci or 426ci a waste of time with the heads available at present...

 

[NC Engine Builder]

Keep in mind the bloomer heads that people are talking about, appear to make a lot of power, and they are the same speedmaster head being discussed here, WITHOUT any offset rockers or anything super trick. Just a killer port job

 

[cookietruck]

I think ive seen comment from IMM about just raising the roof of the port instead of tubing the pushrod hole. Makes the same power.

 

[Earlie A]

Here's a couple of pictures of the pushrod pinch on the Speedmaster port that's currently on the bench. I've finally switched to a 2.08 valve after working forever with the 2.02 valve. Here are some opinions from my perspective, and I do not claim to be correct.

Regarding the pushrod pinch, I would take more width over more height any day. The pushrod pinch is not THE problem with these heads, but it is a problem. As PBR often said, the stock location of the pushrod can support about 330 cfm. I have only been able to get to about 311, but I know more is there. THE problem with these heads is a lack of usable width at the apex of the short turn. We need to be able to get as wide an apex as possible to get the velocity down over the short turn. The problem that the pushrod creates is that air flowing on the floor of the port has to navigate the pushrod turn and then stay attached to the pushrod wall on its way to bore center. The pushrod effectively limits the width of the flow zone going over the short turn. Tubing the pushrod hole lets as much width as possible be utilized. Raising the roof does do some good, but it also can create problems with flow separation around the pushrod turn. Expanding too fast in an area of high velocity leads to flow separation.

One more comment about the pushrod pinch. Enlarging the pinch should only be done after the downstream problems are addressed. Enlarging the pinch as a first step can actually hurt flow. If you think in terms of Bernoulli and pressure vs flow and flow separation it makes some sense, but here's another way to look at it. At high lift the short side (or short side radius, SSR) is under stress. It's doing all it can to hold on to flow without losing the flow over the SSR. If you enlarge the pushrod pinch and nothing else, you've just put additional stress (additional pressure and flow) on the SSR. It can't handle the additional stress and flow separates earlier and peak flow actually goes down. There is a balancing act between the pushrod pinch and the SSR. The pushrod pinch can actually be used to 'tune' the SSR. It's a bit of a crutch, but these low port heads need help sometimes.

Attached are a couple of flow curves that represent my best efforts so far with both 45 and 50 deg seats on the same port with the 2.08 valve. I've tested this port many times, made modifications, epoxied the throat and seat back up and cut it again. The short side and chamber are now mostly epoxy. The big challenge for me is to raise point B without lowering point A. I've still not quite figured out how to remove the entire dip, or if it's even that important. It's more of a challenge at this point.

As far as heads for a 408 stock block - I guess it depends on how you intend to use it. Street use and under 6000 rpm, it's hard to beat the Trick Flow's for the price. All out racing is going to require something ported, which could be custom Speedmasters, Edelbrocks, Trick Flows or the Bloomers. Just my opinion.

 

[Newbomb Turk]

Here's a couple of pictures of the pushrod pinch on the Speedmaster port that's currently on the bench. I've finally switched to a 2.08 valve after working forever with the 2.02 valve. Here are some opinions from my perspective, and I do not claim to be correct.

Regarding the pushrod pinch, I would take more width over more height any day. The pushrod pinch is not THE problem with these heads, but it is a problem. As PBR often said, the stock location of the pushrod can support about 330 cfm. I have only been able to get to about 311, but I know more is there. THE problem with these heads is a lack of usable width at the apex of the short turn. We need to be able to get as wide an apex as possible to get the velocity down over the short turn. The problem that the pushrod creates is that air flowing on the floor of the port has to navigate the pushrod turn and then stay attached to the pushrod wall on its way to bore center. The pushrod effectively limits the width of the flow zone going over the short turn. Tubing the pushrod hole lets as much width as possible be utilized. Raising the roof does do some good, but it also can create problems with flow separation around the pushrod turn. Expanding too fast in an area of high velocity leads to flow separation.

One more comment about the pushrod pinch. Enlarging the pinch should only be done after the downstream problems are addressed. Enlarging the pinch as a first step can actually hurt flow. If you think in terms of Bernoulli and pressure vs flow and flow separation it makes some sense, but here's another way to look at it. At high lift the short side (or short side radius, SSR) is under stress. It's doing all it can to hold on to flow without losing the flow over the SSR. If you enlarge the pushrod pinch and nothing else, you've just put additional stress (additional pressure and flow) on the SSR. It can't handle the additional stress and flow separates earlier and peak flow actually goes down. There is a balancing act between the pushrod pinch and the SSR. The pushrod pinch can actually be used to 'tune' the SSR. It's a bit of a crutch, but these low port heads need help sometimes.

Attached are a couple of flow curves that represent my best efforts so far with both 45 and 50 deg seats on the same port with the 2.08 valve. I've tested this port many times, made modifications, epoxied the throat and seat back up and cut it again. The short side and chamber are now mostly epoxy. The big challenge for me is to raise point B without lowering point A. I've still not quite figured out how to remove the entire dip, or if it's even that important. It's more of a challenge at this point.

As far as heads for a 408 stock block - I guess it depends on how you intend to use it. Street use and under 6000 rpm, it's hard to beat the Trick Flow's for the price. All out racing is going to require something ported, which could be custom Speedmasters, Edelbrocks, Trick Flows or the Bloomers. Just my opinion.

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Yup, the width at the apex issue has brought tears to my eyes more than once.

Junked one of my own heads getting greedy. And a customers heads too. I had to port a set of Edelbrocks to unscrew that deal.

 

[PRH]

I love the perseverance!!
You’re solidly above 300 now.

Any idea what the current runner volume is?
Width at the pinch?

We’re on the same page WRT the pinch/ssr relationship, especially with milder efforts(which is why I advocate for getting after the ssr early on in the porting process).

 

[Newbomb Turk]

Here's a couple of pictures of the pushrod pinch on the Speedmaster port that's currently on the bench. I've finally switched to a 2.08 valve after working forever with the 2.02 valve. Here are some opinions from my perspective, and I do not claim to be correct.

Regarding the pushrod pinch, I would take more width over more height any day. The pushrod pinch is not THE problem with these heads, but it is a problem. As PBR often said, the stock location of the pushrod can support about 330 cfm. I have only been able to get to about 311, but I know more is there. THE problem with these heads is a lack of usable width at the apex of the short turn. We need to be able to get as wide an apex as possible to get the velocity down over the short turn. The problem that the pushrod creates is that air flowing on the floor of the port has to navigate the pushrod turn and then stay attached to the pushrod wall on its way to bore center. The pushrod effectively limits the width of the flow zone going over the short turn. Tubing the pushrod hole lets as much width as possible be utilized. Raising the roof does do some good, but it also can create problems with flow separation around the pushrod turn. Expanding too fast in an area of high velocity leads to flow separation.

One more comment about the pushrod pinch. Enlarging the pinch should only be done after the downstream problems are addressed. Enlarging the pinch as a first step can actually hurt flow. If you think in terms of Bernoulli and pressure vs flow and flow separation it makes some sense, but here's another way to look at it. At high lift the short side (or short side radius, SSR) is under stress. It's doing all it can to hold on to flow without losing the flow over the SSR. If you enlarge the pushrod pinch and nothing else, you've just put additional stress (additional pressure and flow) on the SSR. It can't handle the additional stress and flow separates earlier and peak flow actually goes down. There is a balancing act between the pushrod pinch and the SSR. The pushrod pinch can actually be used to 'tune' the SSR. It's a bit of a crutch, but these low port heads need help sometimes.

Attached are a couple of flow curves that represent my best efforts so far with both 45 and 50 deg seats on the same port with the 2.08 valve. I've tested this port many times, made modifications, epoxied the throat and seat back up and cut it again. The short side and chamber are now mostly epoxy. The big challenge for me is to raise point B without lowering point A. I've still not quite figured out how to remove the entire dip, or if it's even that important. It's more of a challenge at this point.

As far as heads for a 408 stock block - I guess it depends on how you intend to use it. Street use and under 6000 rpm, it's hard to beat the Trick Flow's for the price. All out racing is going to require something ported, which could be custom Speedmasters, Edelbrocks, Trick Flows or the Bloomers. Just my opinion.

View attachment 1716330913

View attachment 1716330914

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Looking at your graph I see the little dip in the 50 that starts about .250 lift. It’s more pronounced with a 55.

I tried for years to understand it, but the last I recall about what we came up with was it was a l/d verses the widths of the cuts under the seat.

I know we found a couple of valve jobs from other people that had narrower cuts under the seat and the dip would go away.

The problem was it would flow more air with the narrow cuts but it always lost power.

I guesstimated that with the narrower cuts the valve job was functioning as a radius and that killed power.

It is there on Chrysler heads, Chevy heads and even a 351 Cleveland I didn’t port but flowed. Some of the Chevy testing was done on AFR 227 raised port heads.

To this day I’ve never seen an explanation for that dip. Or why getting it out of the flow curve hurt power other than my WAG on the valve job acting like a radius.

Edit: bad typing. I meant to say where the curve goes through .250 lift.

 

[Earlie A]

Working on my daughter's house for most of the day. I'll get back to you guys. I appreciate the response and interest.

 

[PRH]

I wouldn’t mind seeing a few bowl & chamber pics to see where you’re at now.

 

[273]

Isn't the main problem with the pinch is velocity not air flow, aren't you suppose to open the pinch to the mcsa needed for that combos cid and rpm so it don't choke off earlier ?

 

[273]

But looking at the 305 T/A heads that were done in 1971, is 360ci too big?
Is going 408ci or 426ci a waste of time with the heads available at present...

Wouldn't it depend on the rpm's your trying to achieve with each displacement ?

 

[Earlie A]

I love the perseverance!!
You’re solidly above 300 now.

Any idea what the current runner volume is?
Width at the pinch?

We’re on the same page WRT the pinch/ssr relationship, especially with milder efforts(which is why I advocate for getting after the ssr early on in the porting process).

Pinch is 1.039 x 2.18. I haven’t measured the volume in a few days. Last measurement was 190cc, but more has been cut out since then.

Edit - corrected the pinch width.

 

[Earlie A]

Looking at your graph I see the little dip in the 50 that starts about .250 lift. It’s more pronounced with a 55.

I tried for years to understand it, but the last I recall about what we came up with was it was a l/d verses the widths of the cuts under the seat.

I know we found a couple of valve jobs from other people that had narrower cuts under the seat and the dip would go away.

The problem was it would flow more air with the narrow cuts but it always lost power.

I guesstimated that with the narrower cuts the valve job was functioning as a radius and that killed power.

It is there on Chrysler heads, Chevy heads and even a 351 Cleveland I didn’t port but flowed. Some of the Chevy testing was done on AFR 227 raised port heads.

To this day I’ve never seen an explanation for that dip. Or why getting it out of the flow curve hurt power other than my WAG on the valve job acting like a radius.

Edit: bad typing. I meant to say where the curve goes through .250 lift.

I’ve been watching the 0.250 lift range as well. I’ve noticed some significant swings there, like up to 10 cfm from a minor change. I’m not quite sure what it is either. I’ve been wondering if it has something to do with the valve just becoming unshrouded at the cyl wall side.

 

[Earlie A]

I wouldn’t mind seeing a few bowl & chamber pics to see where you’re at now.

Here’s the chamber and bowl as it sits now. Valve job is 43 top cut with an 8mm radius blend, then 50/65/75/80. Throat is 88.4% right now.

 

[Earlie A]

Isn't the main problem with the pinch is velocity not air flow, aren't you suppose to open the pinch to the mcsa needed for that combos cid and rpm so it don't choke off earlier ?

You are correct that high velocity through the pinch can become a problem. In a head that has been significantly ported, the pinch may even become THE problem and the choke point. In an unported Edelbrock or Speedmaster I do not believe the pinch to be the main choke, even if it is the mcsa in the entire port. I believe that flow separation across the SSR is what chokes the stock port.

 

[Newbomb Turk]

I’ve been watching the 0.250 lift range as well. I’ve noticed some significant swings there, like up to 10 cfm from a minor change. I’m not quite sure what it is either. I’ve been wondering if it has something to do with the valve just becoming unshrouded at the cyl wall side.

It could be from the cylinder wall but the two guys I was working with could never nail it down.

We thought the steeper seat angle should have allowed the air to be “stood up” for lack of a better term.

In fact, this all started because I was doing a bunch of 50 degree stuff and some 55’s and I was at another shop. I was heading back to the dyno but I stopped in the assembly room to visit with the owner a bit.

And there on the floor was a cylinder head from HRD (I can’t think of the name of that guy now but I think his last name was Dixon) and without measuring it I said those heads have the same 55 degree seat I’m using.

He called BS so I ran back to the shop and grabbed the cutters and it was the exact same.

He wasn’t going to flow them because they were late getting there so I said I’ll grab one and flow it for you.

When I gave him the report his wasn’t happy with the dip. I said I know it’s there, but I haven’t figured out how to get it out yet.

Then he pulled out the report from the heads before they went back to HRD for upgrades. And the 45 didn’t have it. He then flowed them and the dip was there.

Certainly there is a reason for it. We collectively spent way more time to sort it out than we should have. Even HRD (at that time) didn’t have an answer for it

That was when we both bought different tooling and tried to get rid of it. When we did it lost power. Every time.

It may be sorted out by now but I haven’t really tried to figure it out since about 2004.

Oh yeah, lol we had the brain storm of top cutting the valve. I forgot about that one. I tried a bunch of different angles and widths and I found a couple that looked like they’d be killer and it got rid of the dip.

That was worse than changing the valve job. I think that engine was making 2.2-2.4 HP/CID at 9k plus. And top cutting the valve killed power everywhere.

We started talking about changing cam timing and the owner of the engine was on the phone with Comp looking at different loves and such. I took the head back to the bench and reverse flowed the head with the top cut valve and without it.

The reverse flow was staggering. Now that I think about it fuel consumption went up and power was down.

We decided that it was easier (more cost effective) to shelve the cam timing tests and just not top cut the valve and live with the dip.

 

[Earlie A]

It could be from the cylinder wall but the two guys I was working with could never nail it down.

We thought the steeper seat angle should have allowed the air to be “stood up” for lack of a better term.

In fact, this all started because I was doing a bunch of 50 degree stuff and some 55’s and I was at another shop. I was heading back to the dyno but I stopped in the assembly room to visit with the owner a bit.

And there on the floor was a cylinder head from HRD (I can’t think of the name of that guy now but I think his last name was Dixon) and without measuring it I said those heads have the same 55 degree seat I’m using.

He called BS so I ran back to the shop and grabbed the cutters and it was the exact same.

He wasn’t going to flow them because they were late getting there so I said I’ll grab one and flow it for you.

When I gave him the report his wasn’t happy with the dip. I said I know it’s there, but I haven’t figured out how to get it out yet.

Then he pulled out the report from the heads before they went back to HRD for upgrades. And the 45 didn’t have it. He then flowed them and the dip was there.

Certainly there is a reason for it. We collectively spent way more time to sort it out than we should have. Even HRD (at that time) didn’t have an answer for it

That was when we both bought different tooling and tried to get rid of it. When we did it lost power. Every time.

It may be sorted out by now but I haven’t really tried to figure it out since about 2004.

Oh yeah, lol we had the brain storm of top cutting the valve. I forgot about that one. I tried a bunch of different angles and widths and I found a couple that looked like they’d be killer and it got rid of the dip.

That was worse than changing the valve job. I think that engine was making 2.2-2.4 HP/CID at 9k plus. And top cutting the valve killed power everywhere.

We started talking about changing cam timing and the owner of the engine was on the phone with Comp looking at different loves and such. I took the head back to the bench and reverse flowed the head with the top cut valve and without it.

The reverse flow was staggering. Now that I think about it fuel consumption went up and power was down.

We decided that it was easier (more cost effective) to shelve the cam timing tests and just not top cut the valve and live with the dip.

Top cutting the valve? Are you referring to the back cut, or an additional angle between the seat cut and the margin?

 

[Newbomb Turk]

Top cutting the valve? Are you referring to the back cut, or an additional angle between the seat cut and the margin?

I mean putting an angle on the margin of the valve to the face of the valve. So from the face of the valve to the margin.

Some guys call it “clipping” the valve.

It is supposed to (and does) shape the flow around the valve.

But it also makes the valve flow far better in reverse. At overlap you can end up with weird things happening if the intake port pressure is lower than chamber pressure. You get flow moving much better back up the port.

I’ve never really thought about what happens with EFI but I know with a carb the booster has no idea which way the air is moving.

So the air goes through the booster, down towards the valve. Then we get to overlap and the valve is much less an impediment to flow going the wrong way past the valve.

Now the air column, which already has fuel from its first trip down the carb now flows backwards through the booster. Once the system gets back in tune, that same air has now passed through the booster three times and you have 200% (roughly) more fuel than you should.

I know Yunik was big on top cutting the valves (I do a radius on the top of the exhaust valve) but after that I have not done it to another valve.

This was a Comp Eliminator deal and the car owner had money but he didn’t have enough to keep going down the rabbit hole.

We did all the flow testing with steel valves but never on the dyno. Once had a valve shape we wanted to test he would order the valves . At that time Ti intake valves were about 125 bucks each.

When you have 1k in 8 valves and it sucks buttermilk on the dyno you can only do that a couple of times until you get sick to your stomach.

If he has an unlimited budget (or at least more budget) I think he would have continued on testing.


Edit: I just read this post and I hope I’m explaining it correctly. I can’t even remember the angles I was trying but the cut goes from the combustion chamber face of the valve to the the margin.

You are essentially making the margin narrower from the opposite side of the seat.

I think it always flowed more in the forward direction and reverse. That’s usually bad.

 

[Earlie A]

I mean putting an angle on the margin of the valve to the face of the valve. So from the face of the valve to the margin.

Some guys call it “clipping” the valve.

It is supposed to (and does) shape the flow around the valve.

But it also makes the valve flow far better in reverse. At overlap you can end up with weird things happening if the intake port pressure is lower than chamber pressure. You get flow moving much better back up the port.

I’ve never really thought about what happens with EFI but I know with a carb the booster has no idea which way the air is moving.

So the air goes through the booster, down towards the valve. Then we get to overlap and the valve is much less an impediment to flow going the wrong way past the valve.

Now the air column, which already has fuel from its first trip down the carb now flows backwards through the booster. Once the system gets back in tune, that same air has now passed through the booster three times and you have 200% (roughly) more fuel than you should.

I know Yunik was big on top cutting the valves (I do a radius on the top of the exhaust valve) but after that I have not done it to another valve.

This was a Comp Eliminator deal and the car owner had money but he didn’t have enough to keep going down the rabbit hole.

We did all the flow testing with steel valves but never on the dyno. Once had a valve shape we wanted to test he would order the valves . At that time Ti intake valves were about 125 bucks each.

When you have 1k in 8 valves and it sucks buttermilk on the dyno you can only do that a couple of times until you get sick to your stomach.

If he has an unlimited budget (or at least more budget) I think he would have continued on testing.


Edit: I just read this post and I hope I’m explaining it correctly. I can’t even remember the angles I was trying but the cut goes from the combustion chamber face of the valve to the the margin.

You are essentially making the margin narrower from the opposite side of the seat.

I think it always flowed more in the forward direction and reverse. That’s usually bad.

I can’t see how that type of top angle would help flow in the proper direction at all. I can see how it promotes reversion.

I would like to play around with a small top angle between the seat cut and the margin. I’ve done it once with some mixed results, but never spent any real time on it. I think the general consensus in the industry is that this type of cut effectively reduces the valve diameter because the seat cut is now a smaller diameter.

 

[Earlie A]

I love the perseverance!!
You’re solidly above 300 now.

Any idea what the current runner volume is?
Width at the pinch?

We’re on the same page WRT the pinch/ssr relationship, especially with milder efforts(which is why I advocate for getting after the ssr early on in the porting process).

Port volume for the 50 deg test was 196cc. It would have been around 192cc for the 45 deg test.

 

[PRH]

I believe that flow separation across the SSR is what chokes the stock port.

I agree.

On mildly reworked factory SBM heads, if you don’t do a fair amount of SSR layback, it’s not at all uncommon for me to see the flow continue to drop after the separation starts.
In other words, the flow gets worse and worse as the lift increases.
This is obviously not a problem with the area at the pinch getting worse as the valve is opened further, but rather the area of the bowl/throat getting progressively shut down more as the valve is opened.
In this scenario, if opening the pinch “more” exacerbates the situation, then imo, it’s not helping with power output.

It would make for an interesting dyno test though.
Bigger pinch with more separation and less high lift flow vs a smaller pinch with less separation and more high lift flow.

Pinch is 1.039 x 2.18.

Not taking into account the corner radii, theoretically enough for about 330cfm.

 

[Earlie A]

I agree.

On mildLy reworked factory SBM heads, if you don’t do a fair amount of SSR layback, it’s not at all uncommon for me to see the flow continue to drop after the separation starts.
In other words, the flow gets worse and worse as the lift increases.
This is obviously not a problem with the area at the pinch getting worse as the valve is opened further, but rather the area of the bowl/throat getting progressively shut down more as the valve is opened.
In this scenario, if opening the pinch “more” exacerbates the situation, then imo, it’s not helping with power output.

It would make for an interesting dyno test though.
Bigger pinch with more separation and less high lift flow vs a smaller pinch with less separation and more high lift flow.

I agree. It’s hard to know what the stopping point is without the dyno to verify.

 

[Earlie A]

I agree.

On mildly reworked factory SBM heads, if you don’t do a fair amount of SSR layback, it’s not at all uncommon for me to see the flow continue to drop after the separation starts.
In other words, the flow gets worse and worse as the lift increases.
This is obviously not a problem with the area at the pinch getting worse as the valve is opened further, but rather the area of the bowl/throat getting progressively shut down more as the valve is opened.
In this scenario, if opening the pinch “more” exacerbates the situation, then imo, it’s not helping with power output.

It would make for an interesting dyno test though.
Bigger pinch with more separation and less high lift flow vs a smaller pinch with less separation and more high lift flow.

Here’s another thought I’ve been mulling over. As the short side is laid back, the angle of approach of the air relative to the throat gets shallower. This in effect ‘tilts’ the throat and makes it more oval, which reduces flow area. I know these aren’t new concepts, just new to me.

 

[PRH]

When it comes to many, let’s call them “entry level” bolt on performance heads, they often still retain certain design characteristics that aren’t great for flow, in an effort to make them usable in a wider range of applications.
Low ports and less than ideal SSR forms being some of those characteristics.

 

[273]

I agree.

On mildly reworked factory SBM heads, if you don’t do a fair amount of SSR layback, it’s not at all uncommon for me to see the flow continue to drop after the separation starts.
In other words, the flow gets worse and worse as the lift increases.
This is obviously not a problem with the area at the pinch getting worse as the valve is opened further, but rather the area of the bowl/throat getting progressively shut down more as the valve is opened.
In this scenario, if opening the pinch “more” exacerbates the situation, then imo, it’s not helping with power output.

It would make for an interesting dyno test though.
Bigger pinch with more separation and less high lift flow vs a smaller pinch with less separation and more high lift flow.



Not taking into account the corner radii, theoretically enough for about 330cfm.

I meant in a running engine that if the rest of the port was up to the task for (cid x rpm x ve%) that the pinch area should to be sized (it's generally the mcsa) for the application (cid x rpm x ve%) so it don't choke off before desired peak rpm and have decent over rpm (shift points). More so for that then any flow increase that may come from it. In other words if the push rod needed to be moved it would be for the needed mcsa more than an increase in flow, far as I understand it.