Wide and Flat Torque Curve

Nice but having run a high compression Cleveland on the street, I have my doubts that it can be run on pump gas at all.

Certainly you would HAVE to limit the total advance to 28 degrees.

In my case initial advance needed to be limited to 12 degrees otherwise it would ping right off of idle.

Since so many are now running these monster engines, maybe someone should bring up the subject of the limits of the ZF now?

I know the 427 Fords were past the reliable limit of the ZF in the GT40 MkII's and an entirely different transaxle needed to be used in them.

Doug, those are Scott Cooks heads, they have high swirl combustion chambers. They can run 11:1 on the street with pump gas OK. 28 degrees ignition is full advance with those heads!

Corey, comparing two random engines proves nothing. To do a comparison between parts you need to be swapping them on the same short block, changing only one thing at a time, the parts in question, whilst other important things like cams, pistons, carbs remain the same.

You're taking the thread in the wrong direction. My point is admiration of that flat torque curve, not a head comparison. Its OK for me to admire the torque curve of that motor, it doesn't detract from TFS heads in any way. You're welcome to like TFS heads. I don't dislike them. But your post seems quite rude to me. What is your point, what are you trying to accomplish. Do you insinuate nobody should purchase SCM heads?

sothe high swirl heads are they 4v style or 2v or something different? i like the fact they produce good hp and torque but are they too much for the street?

quote:

Originally posted by 73 l:
so the high swirl heads are they 4v style or 2v or something different? i like the fact they produce good hp and torque but are they too much for the street?

Here's a link to the thread regarding SCM (Scott Cook Motorsports) heads.

Scott Cook Heads

The SCM heads are a modern head, designed by Darin Morgan, designed in the spirit of the 4V head. They are a stuffed 4V port head, the same concept as the CHI 3V head. The port inlet is about the size of a 2V port inlet, but the opening is raised so that the roof of the port is the same height as the roof of a 4V port. To look at it a different way, start with a 4V port, fill in the left hand side of the port and fill in the floor of the port until it is approximately the size of a 2V port.



Darin Morgan designs induction systems for Reher Morrison Racing engines, he's a recognized authority on the subject; he teaches induction system design, and he has written a text book on induction system design. I believe it is an awesome opportunity for regular Joes like you and I to be able to purchase a product developed for our cars by someone with the professional credentials of Darin Morgan.

Imagine bolting a set of these heads on your 351 cubic inch motor, adding a mild hydraulic roller cam like a Crane HR216, and having about the same performance as a Corvette LS7 motor. They are not "too much" for the street. They can be as mild or as wild as you want them to be. I don't need 560 BHP personally, 400 BHP is just fine (scary enough for me). From my point of view, as a life long fan of the 4V Cleveland motor, these heads provide the opportunity to jump ahead 40 years and modernize the 4V Cleveland with state of the art technology. Just the way the original 4V heads were state of the art in 1970.

A lot of guys want to talk dyno numbers and air flow numbers ... that's fine ... but these motors all produce way more power than street tires can harness. Personally I am amazed by the width and flatness of that torque curve.

-G

George,

Very cool numbers!!!

Is the design concept of the smaller port to increase velocity?

Where would one WANT to use a 4V sized port?

I am confused as I though one of the claims to fame of the Cleveland was the BIG ports on the heads???

quote:

Originally posted by Cowboy from Hell:
Doug, those are Scott Cooks heads, they have high swirl combustion chambers. They can run 11:1 on the street with pump gas OK. 28 degrees ignition is full advance with those heads!

Corey, comparing two random engines proves nothing. To do a comparison between parts you need to be swapping them on the same short block, changing only one thing at a time, the parts in question, whilst other important things like cams, pistons, carbs remain the same.

You're taking the thread in the wrong direction. My point is admiration of that flat torque curve, not a head comparison. Its OK for me to admire the torque curve of that motor, it doesn't detract from TFS heads in any way. You're welcome to like TFS heads. I don't dislike them. But your post seems quite rude to me. What is your point, what are you trying to accomplish. Do you insinuate nobody should purchase SCM heads?

George, Scotts heads are beautiful. I'm not insinuating anything negative about them.

I think Corey's post is fair. I think there is going to be a similarity between all of them.

Octane rating of gasoline is in effect a statement of the presure the atomized fuel will withstand in the combustion chamber without detonating without a spark. Also know as dieseling.

With a static compression ration of 11:1, there is no possible way 93 pump octane can run without detonating virtually at idle, or just off of it, without 1) limiting the amount of total ignition advance 2) timing the exhaust to fool the engine and leave the exhaust valve open long enough to blow some of the combustion pressure out of the exhaust 3) limiting the rate of ignition advance.

Apparently Scotts test is a testiment to finding the balance between, pump gas, cam timing, and ignition timing.

There are lots of magazine dyno tests where the adjustment to detonation on the dyno with pump gas is to reduce total advance to that number, 28 degrees.

Big block Chevys and Mopars like that number too.

Increasing total advance increases combustion pressure similarly to razing static compression ratios. You need more octane, i.e., less sensativity to detonation in order to do that. Todays pump gas just won't cut it.

In fact I even tried the Sunoco 102 unleaded Racing gas and it still was useless. 106 is the only thing that is going to work, which is fine if I want to pay $7.50 a gallon for it and tow a tanker of it behind me with it.

You can swirl all the mixture you want around in those heads and that isn't going to reduce the presure in the combustion chamber.

It is cam timing, ignition timing, and static compression ratio.

Put Sunoco 106 racing gas in that engine on the dyno, retime it to where it should be, 34-35 degrees and you are going to pick up 100 hp.

The point is, 28 degrees total timing, is a dyno trick to make a high compression engine run on pump gas.

The better solution is to run a compression ration of around 10:1 with those heads, or any heads, run full advance of 34-36. Slow the advance down so it isn't all in to around 5,000 engine rpm.

That would be realistic and wouldn't be a dyno trick to make your product look like something that it isn't.

Furthermore, limiting to a total of 28 degrees effects adversely the response or crispness of an engine. It really should only be done as a last resort.

Been there, done that. Maybe the Aussie's think because they are upside down, then the laws of Physics don't apply to them, I don't know?

Doug Its not a dyno trick. These heads only call for 28 degrees total timing, no matter what the compression ratio is. These heads will easily run on a 1/2 point more compression than the original combustion chamber design; in other words 11:1 instead of 10.5:1.

Scott the main thrust of Darin Morgan's design is not gas velocity. That's always a component of the design, its just not something you and I should have to worry about if the designer does his homework, however gas velocity is kicked around a lot in magazine ads and what not. The heads designed by Darin Morgan have about 249cc intake port volume, a ported iron 4V intake port is about 250cc. The port entrance of the 4V port is deceiving, the port gets much smaller further inside. Darin Morgans port has a much more constant cross section. But the two ports have about the same average cross-sectional area. The 4V port is designed the way it is because the Ford engineers were doing some gas management tricks that worked quite successfully, Darin Morgan's port is a more "straight forward" port design. The 4V port is tuned for a powerband of 3000 to 7000 rpm, the lower end of the 4V powerband relies upon camshaft design & intake manifold design. I can't say what the powerband of the SCM heads is. Both are designed for wide flat torque curves.

The computer is turning off.


-G

quote:

The computer is turning off.

I hear you... I wish that some people didn't find the need to debate EVERY post...

so the size of scotts ports matches the narrow restrictions of the 4v port as it flows toward the valve?

quote:

so the size of scotts ports matches the narrow restrictions of the 4v port as it flows toward the valve?

It sounds like, from George's description, that Scott's port design is a more consistent size as it flows down towards the valve. Since George pointed out that the volume is about the same, it would indicate that the size of the port is larger than the 4V closer to the valve. This is what I got out of the description...

The cross-sectional area of the port's runner is reasonably small and constant along the length of the runner, the extra volume is gained via a large valve pocket. The large valve pocket slows the velocity of the gases so they can make the turn into the valve pocket and distribute evenly around the back side of the valve.

The sharper the turn, the more the gases must be slowed down. High ports turn less sharply, low ports turn more sharply.

Sizing the port has more to do with powerband than velocity. The gases in a high performance motor gain velocity as the result of piston speed, not port cross section. If you reduce the size of the port too much, to gain gas velocity at low piston speeds, the port will act as a restriction to gas flow at higher speeds, and the gain in inertial energy at low speeds is usally not enough to perform any usful benefit. That is as per Mr. Morgan.

As far as I'm concerned, discussion of port height is more important than the usual discussion of air velocity. This is one good example, where a high velocity port looks like a lower velocity port because of the large volume number. But the large volume is the result of a large pocket, not a large cross-section runner. The large pocket was needed due to port height!

Another aspect of the design, the ports are very non-turbulent, air flow keeps increasing as the valve keeps opening, all the way out to 1" valve lift! Mr Morgan says the exhaust port is the best "low port" he's ever designed. That's saying a lot. This aspect is also more crucial than the usual "small ports" and "high gas velocity" sales talk.

One last point I'd like to make, the price of these heads aren't cheap, but that is because Scott refuses to have them cast in China. He has them cast domestically in Australia. I think a lot of us would give him kudos for that.

Now back to that torque curve ... isn't anyone besides me impressed?


-G

quote:

Now back to that torque curve ... isn't anyone besides me impressed?

I am extremely impressed.

That car is going to be a blast to drive. The torque is what makes the car feel powerful with the push you back in the seat type of feeling.

Thanks for sharing!

Considering that it is only a 393 I have to be impressed. These numbers look very much like a good 427 medium rise Ford numbers.

I think its great Scott and Darin brought another head to the market, but I did't think Corey was out of line or rude to make comparisons. I mean how can you say something is an improvement or not unless you have something to compare it to? Its really hard to make apples to apples comparisons considering all the variables that go into building an engine and what kind of performance and operating characteristics you are willing to sacrifice for, but if someone is looking at buying a new set of heads, they should know whats out there and what people have been able to build. There are a lot of cleveland heads on the market, so its nice to be able to critique the benefits/drawbacks of each one, think that is what these forums are for aside from keyboard racing The fact is there is no one best head choice for every build.

To me this head appears to be competing at the top of the street offerings arena from TFS/Ebrock/CHI/AFD since it retains factory header/intake style locations vs high port offerings, probably more with the CHI versions since it has CNC work done. Even the intake/heads Scott mentioned that he tried to retain the look of the factory heads/intake in the external castings. I think that is great if you are out grudge racing people and trying to pull the wool over someone or just want your factory street car to retain that appearance. Hell I'd paint the stuff blue haha. Seems like most folks advocate a 225cc head minimum for a windsor or cleveland stroker, so I don't see how this head would be too large.

I think doug brought up a good point though, these dual plane strokers done right make a ton of torque which is not exactly what any transmission including the ZF want for longetivity. I'm honestly baffled to see dual planes on 400" strokers given the ZF's limitations. That and a 400" engine wants to breath! I get most of the builds here are for people who want streetable performance, but my belief is the single plane gets an unfair reputation of being a race only piece. I really feel this is a huge misconception especially when you get into the stroker small blocks which can pull a ton of air from a common plenum. I also get the argument is that lowering the powerband can make it more usable for a streetcar with more reliable performance because of less strain on the valvetrain and a powerband more suited for a street car. Not sure how you are going to plant 500+ ft lbs of torque on the street without pedaling the skis though. Are we doing this for bragging rights? I thought the whole history of the cleveland was to wind them up with the large port heads, and that is what made them shine over every other small block. Might as well stick a dumptruck windsor in the thing if you just want to rev it to 5500. No offense to the windsor folks

quote:

Originally posted by Hustler:

... I'm honestly baffled to see dual planes on 400" strokers given the ZF's limitations. ... my belief is the single plane gets an unfair reputation of being a race only piece ...

I would turn that around on you and say that Scott's manifold seems to make a good argument that dual plane manifolds have an unfair reputation for only being low rpm manifolds. This 393 cubic inch motor hasn't run out of air at 6600 rpm. It hasn't made peak horsepower yet either.

That's a reasonably big cam, the dual plane manifold will provide better intake manifold vacuum for PCV, power brakes, vacuum advance and auto trans modulator valves.

I agree however it would be nice to bolt on a single plane from Terry Parker or TFC and see how the motor performs with a single plane manifold.

-G

I don't know when I look at those old dual planes I look at them as a product of limitations keeping a long runner package at a height where the carb pad was low enough to fit under a factory sedan without a huge hood to fit the air cleaner. Those runners are cramped and exposed to heat soak. I shouldn't make it sound as though a long runner intake is bad, its not, just the package most "Carbureted" dual planes come in seems opposed to anything relating to performance. When I look at the long runner EFI intakes its a different story, they usually involve the 302's lower deck height, affording a completely different upper manifold. This in turn offered more flexibility to arrange the port and the entry into the head with a longer runner.

Isn't that a great torque curve?

Yes but couldn't the intake be holding back power and torque across the whole board? That is my thought and I think what Corey was alluding to as well.

Scott's dual plane intake manifold is not grampa's (me) intake manifold. It has a tremendous amount of development time and money invested in it. Scott's goal was to equal or better the performance of the single plane manifolds. If it leaves anything on the table, it doesn't leave much; it will give the single plane manifolds a run for their money.

The manifold & heads combined make for one very sweet induction system. This is not a run-of-the-mill product. This is an induction system designed by Darin Morgan.

That is indeed a flat curve. Here is another you might enjoy. . This is also from a 394 and yes the RPM is correct.

HP and torque curves always cross at 5250 rpm...are you sure these curves are correct?

Jack

Jack

Look at the scaling along the left hand & right hand borders of the graph. The scaling for horsepower & torque are different, if the scaling was the same they would cross as expected.

-G

The owner of the motor in question has commented that after some development work and more dyno time his motor ultimately made 549 foot pounds torque and 627 horsepower at 6700 rpm. The torque was 500 foot pounds or more between 3500 rpm and 6500 rpm. The owner also commented a TFC manifold (single plane) found 10 extra foot pounds through the mid-range, but did not make 1 more horsepower on top.

Scott mentioned the motor ran on 98 octane Australian gasoline, which would be equivalent to 93 octane in the US and Canada. Scott also commented it used one of his dual plane manifolds, modified, nothing fancy just lots of R&D to get it right.

I know everyone is into the big numbers, chest thumping and bragging rights. That's cool. The owner is happy with the motor, and Scott is rightfully proud. Those of you who know me understand that's just not where my head is at any longer. If peak horsepower were only 400 bhp I'd still be as amazed at the width and flatness of the torque curve.

If somebody shares the final dyno curve with me I'll post it up for you guys.

-G

28 degrees total timing is consistent with controlling the combustion chamber pressure to avoid detonation of US 93 octane pump gas.

If you were detonating the fuel at somewhere in the 30 to 36 degree range and you lowered the advance to a point where it no longer detonated, you would show an increase in both hp and tq.

That is an indication that the engine was detonating and there were no other obvious indications.

A big engine might not show it except in the dyno numbers, particularly if the combustion chambers had been modified.

The controlling factor to the entire experiment is the octane of the fuel used. You must determine at what pressure the 93 will detonate and then arrive at solutions on how not to exceed that.

Static compression ratio, total timing and camshaft timing are all major contributing factors to that.

If you can control detonation with chamber design alone, without a computer control of the ignition and tailoring those factors to comply to the fuel requirements, then you had better patent this chamber design because you have change the laws of physics and you may have also discovered Warp Drive for the Enterprise?

Changing to a single plenum intake manifold would change the characteristics of the engine and is just a tuning choice.

It is entirely possible that this dual plane will out perform the single plane entirely. Especially since this engine seems to be limited to 6700rpm. Particularly if it has been modified and flowed itself to compliment the air flow characteristics of the heads and induction it is mated to? I'll bet this one was seriously flowed before the dyno test?

The main advantage to the single plane would be above that.

The Yates and Nascar "Ford" single plane manifolds were created to yield hp gains up to 9200 rpm. That right there should be an indication of which is the "better" intake to use for this application.

Anyway you look at this, this is really a hell of an engine.

It out preforms the race 427 Fords at every level at a lower cid number.

The 427 Ford is now quite expensive to build. I don't know if this Australian Cleveland is going to have any price advantage. Looks like a dollar monster to me?

I mention them simply because I use those as the standard by which I measure BB performance and this 393 like it or not is a "BB" in that sense.

BUT there are other issues to consider with it. First of all, it may not necessarily been built for a Pantera.

As such to run it hard in one, you have to consider the longevity of the ZF with it.

I suppose the term "running it hard" now has to be defined as well. Looking at those torque numbers, it is running hard just idling, sitting there doing nothing?

Second as has been mentioned here, does it have the same small block "rev-ability"?

It would appear from the numbers posted that it is just a big bully that is going to break traction consistently just off of idle?

To me, that isn't what I like in an engine.

This really is just a bench racing post with debates over what taste in an engine should be and whose manhood is bigger then the other guys?

it could be worse, we could be debating which crate motor to buy from walmart.

quote:

it could be worse, we could be debating which crate motor to buy from walmart.

I am not even going to try and understand what that means...

George, thanks for pointing out the difference in torque and HP scaling that I obviously did not notice.

Jack

is it cowboy from hell or granpa from hell just a joke. but interesting about the the scale of the hp vrs torque what would it look like scaled properly?

Grampa from hell

The formula for horsepower is (torque x rpm) ÷ 5252

so horsepower = torque at 5252 rpm.

When the scaling for horsepower & torque are the same, then the torque curve & horsepower curve will always cross at 5252 rpm.