SBM Edelbrock/Speedmaster Head Data

[PRH]

When dealing with stock or entry level type heads, many times the rest of the port isn’t up to the task.
On that type of head, especially in milder applications, the pinch is not the limiting factor for power production.

 

[273]

When dealing with stock or entry level type heads, many times the rest of the port isn’t up to the task.
On that type of head, especially in milder applications, the pinch is not the limiting factor for power production.

I could see that, the other day was moving stuff around and came across my old J heads and couldn't believe how small the ports are

 

[polyjohn]

Wow Guys, just brilliant and very technical all at once!

The long and short of it is:-

If you haven't got a decent bench, then don't think about all out porting DOH!

There is an old adage, ''if it looks right, then it probably is right''.

Can a SM 170 head be ported to 300cfm without a degree in science?

Great work porting guys, you take my breath away with these flow numbers.

On a slightly different note, are the CNC ported SM heads any good, what do they flow???

 

[Earlie A]

Wow Guys, just brilliant and very technical all at once!

The long and short of it is:-

If you haven't got a decent bench, then don't think about all out porting DOH!

There is an old adage, ''if it looks right, then it probably is right''.

Can a SM 170 head be ported to 300cfm without a degree in science?

Great work porting guys, you take my breath away with these flow numbers.

On a slightly different note, are the CNC ported SM heads any good, what do they flow???

Here's how the stock SM, the CNC SM and the stock Trick Flows tested on my bench. All 2.02 valves.

Porting the SM to 270-280 is not that difficult, especially if using a 2.055 or 2.08 valve. Getting to 300 takes some work and some testing/cutting machinery.

 

[cookietruck]

That TF port really starts working at .250”

 

[Earlie A]

That TF port really starts working at .250”

Yes, compared to the other two it keeps working for longer.

 

[273]

One of the guy's at TF said for their street heads they really focus on flows between .300-.500" lift.

 

[PRH]

Imo, the curve on the cnc SM is as unimpressive as it is because it’s poorly executed.

With a more refined throat and valve job, the numbers in the middle could be noticeably better.

They’re in it for the quick cash and banking on the CNC buzzword for sales.

It’s pretty bad when there are areas near the middle of the curve where the ootb untouched head is better.

 

[273]

Imo, the curve on the cnc SM is as unimpressive as it is because it’s poorly executed.

With a more refined throat and valve job, the numbers in the middle could be noticeably better.

They’re in it for the quick cash and banking on the CNC buzzword for sales.

It’s pretty bad when there are areas near the middle of the curve where the ootb untouched head is better.

And the sad part is how hard would of it been to find someone to do a decent port job they could of copied, even now how hard would it be to update their cnc program to a better port shape.

 

[Earlie A]

Imo, the curve on the cnc SM is as unimpressive as it is because it’s poorly executed.

With a more refined throat and valve job, the numbers in the middle could be noticeably better.

They’re in it for the quick cash and banking on the CNC buzzword for sales.

It’s pretty bad when there are areas near the middle of the curve where the ootb untouched head is better.

I could not agree more. Large bowl and a 93% throat on my CNC SM head. I hope other heads are better than mine.

 

[PRH]

The problem isn’t really in the bulk of the cnc “porting”…….., it’s detail work in the seat and bowl area, and how well that transition is sorted out.

And the fact is, it takes expensive machines, with operators given ample time to get that transition done right.
When you’re building a product around a low price point, that just doesn’t fit into the equation.
So, what you get instead is a blown out bowl that can be made to mate up with a way less than optimal ootb valve seat shape.
Once the valve has been opened up enough to get clear of the influence from the seat, the cnc work done upstream finally starts to reveal itself.
Which, in EA’s example is after .450” lift.

Without getting into too much detail and derailng this thread, an example of what I’m talking about are these results from a CNC ported BBM head.
Without doing any work other than in the immediate seat/bowl area(no additional porting in the runners), by implementing a more air flow friendly seat profile, adding a small back cut to the valve, and blending away a little ridge around the OD of the valve job I was able to pick up:
4.8@.300
15.7@.400
15.7@.500
15.0@.600
13.8@.700
With basically zero gain in runner volume.

 

[polyjohn]

Keep it coming GUYS!

Why is the CNC SlowMaster so POOR???
I nearly opted for a set and glad I didn't now.

Guess its Trickflow for all out racers then...
(Twice the price is probably worth it)

 

[polyjohn]

SM and TF coolio indeed, no drop off at .550.

300cfm is a great number for both Big and Small block.

 

[273]

Do you plan taking your work to the dyno and or track stage ?
Seems like the next logical step, I'm sure you could partner up with some of the peeps here if needed to do so.

 

[Earlie A]

Do you plan taking your work to the dyno and or track stage ?
Seems like the next logical step, I'm sure you could partner up with some of the peeps here if needed to do so.

I have no idea where this is going. I'm still learning and trying to figure some things out, not the least of which is that irritating dip at 0.650" lift. Nonetheless, it was a productive week. Here's the results of about 60 modifications and flow tests. Thanks for the interest.

 

[Newbomb Turk]

I have no idea where this is going. I'm still learning and trying to figure some things out, not the least of which is that irritating dip at 0.650" lift. Nonetheless, it was a productive week. Here's the results of about 60 modifications and flow tests. Thanks for the interest.

View attachment 1716334996

View attachment 1716334997

IMO at that lift you are dealing with a seat/chamber issue.

How to address it is the question.

The 50 degree valve job certainly takes a bigger hit up there.

Have you tested the ports just like they are at the highest pressure your bench will pull and then say maybe at 10 inches and see what those curves look like?

That may get you going in the correct direction.

 

[Earlie A]

IMO at that lift you are dealing with a seat/chamber issue.

How to address it is the question.

The 50 degree valve job certainly takes a bigger hit up there.

Have you tested the ports just like they are at the highest pressure your bench will pull and then say maybe at 10 inches and see what those curves look like?

That may get you going in the correct direction.

Are you saying a 50 deg seat will dip more than a 45?

 

[Newbomb Turk]

Are you saying a 50 deg seat will dip more than a 45?

No, I’m saying that looking at your flow curves the 50 took a bigger dip than the 45.


I forget the valve size exactly but at a 2.055 valve the .25 l/d ratio is .5138 lift and a 2.08 valve is .520 so you should be well past where the valve has a bunch of influence on the flow curves.

I’m a bit bewildered by that curve. Usually at high lifts the 50 and steeper seats don’t do that if the port has the cross section to support it.

Have you put the valve in the guide from the spring side and flowed both ports??

That may get you going the right direction.

 

[Earlie A]

No, I’m saying that looking at your flow curves the 50 took a bigger dip than the 45.


I forget the valve size exactly but at a 2.055 valve the .25 l/d ratio is .5138 lift and a 2.08 valve is .520 so you should be well past where the valve has a bunch of influence on the flow curves.

I’m a bit bewildered by that curve. Usually at high lifts the 50 and steeper seats don’t do that if the port has the cross section to support it.

Have you put the valve in the guide from the spring side and flowed both ports??

That may get you going the right direction.

Sorry for the confusion, but the two tests shown this time are both 50 deg. They are the same port, just showing the progress over 1 week. 1/8 identifies that it's cylinder 1 or 8, then the date is shown.

So, the bigger dip is a result of lots of work on the short side and some in the chamber.

And it is definitely an area thing. Once the short side is lost, a majority of the air is going over the valve and toward bore center. Finding area in the 0.550"-0.650" lift range is the key. It's hard to do. Laying back the short side helps some, but eventually the mid lift flow will suffer. I'm going very slowly at this point because I have a pretty good port going. Don't want to mess it up.

Haven't flowed with the valve upside down lately, nor have I tried the different test pressures. Maybe I'll try that in the morning.

 

[Newbomb Turk]

Sorry for the confusion, but the two tests shown this time are both 50 deg. They are the same port, just showing the progress over 1 week. 1/8 identifies that it's cylinder 1 or 8, then the date is shown.

So, the bigger dip is a result of lots of work on the short side and some in the chamber.

And it is definitely an area thing. Once the short side is lost, a majority of the air is going over the valve and toward bore center. Finding area in the 0.550"-0.650" lift range is the key. It's hard to do. Laying back the short side helps some, but eventually the mid lift flow will suffer. I'm going very slowly at this point because I have a pretty good port going. Don't want to mess it up.

Haven't flowed with the valve upside down lately, nor have I tried the different test pressures. Maybe I'll try that in the morning.

Ok, I got it now. I’d test with different pressures and then flow the port with the valve upside down.

I think that might give some direction.

But your flow curves definitely have a strange dip.

I’ll be glad to learn what it is when you figure it out.

 

[Earlie A]

Ok, I got it now. I’d test with different pressures and then flow the port with the valve upside down.

I think that might give some direction.

But your flow curves definitely have a strange dip.

I’ll be glad to learn what it is when you figure it out.

I think it could be chamber shrouding on the long side. The valves are sunk 0.080 to 0.090. This means there would be that much additional shrouding on the plug side. Look how quickly the flow rises at 0.700-0.950 lift. The valve is getting clear of the chamber. I bet a surface cut on the deck face would clear it right up.

 

[Newbomb Turk]

I think it could be chamber shrouding on the long side. The valves are sunk 0.080 to 0.090. This means there would be that much additional shrouding on the plug side. Look how quickly the flow rises at 0.700-0.950 lift. The valve is getting clear of the chamber. I bet a surface cut on the deck face would clear it right up.

I can say the best set of heads I did was a BBC casting. I forgot what castings they were but I had to use a bunch of filler in the ports bit at 1 inch of lift the flow curve was still going up.

And by that time I had sold my bench so a third party did the before and after testing.

With a tunnel ram and 555 inches it went 1100 NA and he dropped a 400 shot on it.

He rattled the tires so hard so many times it knocked some of the filler out.

The guy who fixed the heads took all the filler out and the engine never made the same power.

Those heads were only flowed twice. Before and after. I had done enough of them that I went for it.

That was with 50 degree seats. I probably should have been using a 52 degree seat on the exhaust.

My point is you are drinking straight from the fire hose!! Eventually you’ll get to the point with certain castings that you will know where the issues are and you’ll just flow the port where the issues are to a make sure you have them nailed.

All this data will pay off big time down the road. Any tests you can go and any test you can think of will give you information.

Keep pounding on it. BTW, a low port 18 degree head is a tough way to learn.


All that data will make it so you can charge enough to make porting worth it.

Once you get the flow numbers you want, you can go to the dyno. Then the track. When all three agree you’ll be making smoke. And you can charge extra for it.

Edit: the BBC castings were Brodie. I can’t remember the exact head but it wasn’t my first choice.

 

[polyjohn]

It all looks good to me Earlie-A!

I can see from my new SM heads that arrived today that to ports are BIG!

300cfm at 1/2'' lift is a winner, winner, Chicken dinner indeed!

All we have to do as ''non benchers'' is find that number, without ruining our lovely SM heads.

Keep up the good work E-A and all that have chipped in.

PolyJohn waiting for POLY head numbers now please E-A.

 

[polyjohn]

I am going to compare the SM head to my Weslake 'J' head cutaways.

Much taller port floor and a slight ''wall hump'' as per all late Mopar iron heads.
The area open to the valve, next to the port wall is tiny in comparison.

 

[Earlie A]

I am going to compare the SM head to my Weslake 'J' head cutaways.

Much taller port floor and a slight ''wall hump'' as per all late Mopar iron heads.
The area open to the valve, next to the port wall is tiny in comparison.

View attachment 1716335340

View attachment 1716335341

That hump on the floor at the common wall is a problem area and a danger area for sure. The port on the left looks quite nice!