Cam recommendations for present build

[Neil Harvey]

I came on here to give some opinion. I am the first to admit I'm not that smart. I do have a resume that includes some engine experience, so I guess I can at least keep up with some on here.

I never stated we made our cams symmetrical. maybe you could take the time to re read my post.

As for being new to me, no but we had not done as many new A symmetrical designs for the early 911 engines. If others have then that's great. Why then do they not sell them.

I offer up my opinions with the only reason but to pass along anything I can that may be of help to others. I don't come on here to get into a back and forth who is right, nor do I feel my opinion is the only one. And I do not think my stuff is the best. Its the choice of the customer to make that decision.

My friend, my advice to you. Don't poke the bear to often, bears have habit of biting back.

[Henry Schmidt]

Originally Posted by Neil Harvey

I came on here to give some opinion. I am the first to admit I'm not that smart. I do have a resume that includes some engine experience, so I guess I can at least keep up with some on here.

I never stated we made our cams symmetrical. maybe you could take the time to re read my post.

As for being new to me, no but we had not done as many new A symmetrical designs for the early 911 engines. If others have then that's great. Why then do they not sell them.

I offer up my opinions with the only reason but to pass along anything I can that may be of help to others. I don't come on here to get into a back and forth who is right, nor do I feel my opinion is the only one. And I do not think my stuff is the best. Its the choice of the customer to make that decision.

My friend, my advice to you. Don't poke the bear to often, bears have habit of biting back.

I did reread your post and I did misunderstand what you wrote. I took your use of "A symmetrical" to be a differentiation from asymmetrical.
Why all the angst. I'm simply asking questions. I misunderstood your "self promotional" [your words] post about new innovations, I apologize.
Now for the threat....."don't poke the bear" I always get a kit out of keyboard warriors. Save it for the younger guys who don't know who you are.

[Dpmulvan]

Originally Posted by PeteKz

Dpmulvan: Curious, why are you picking the JE pistons?

Because they were $1200.

[Henry Schmidt]

Originally Posted by PeteKz

Dpmulvan: Curious, why are you picking the JE pistons?

Originally Posted by Dpmulvan

Because they were $1200.

There are a few good reasons to use JE pistons.
First they are a relatively high quality forgings. We used them 30 years ago when Snake was still finding his way. They were horrible then. As time went on, JE got some better equipment, trial & error experience and some input from builders like myself so the pistons started to work better in Nikasil cylinders.
Next there is rapid development and production time. If you have a special design in mind [dome shape, ring package, forging configuration] after markets pistons offer that.
Third there is a reasonable price. Building these old motors is a crazy expensive proposition. If you can find a quality part that offers the configuration you want at a more reasonable price, why not use it.

Now all that said, we don't use JE pistons as much as we used to. We're finding working with CP more compatible for our needs. We like their forgings, quick development times, small custom run requirements and ease of communication. They are a little more expensive but for the reasons I listed, they are the best option in most cases. We're building a 906 that needs pistons and the off the shelf piston that Mahle offers don't fix our requirements.

[Henry Schmidt]

Originally Posted by PeteKz

Henry, thanks for posting that graph of power vs. spark timing. I'm not sure I understand it, as I'm looking for some RPM reference relative to spark advance. Could you explain it a little please? Thanks in advance (pun intended).

Sorry Pete but I'm not sure what you're asking.
Are you asking for the advance curve for a specific engine? If that is your question, I need a lot more information.
Building an engine is a symbiotic adventure. All parts have to work together.
That is why "mystery" cam specs strain credulity.
How can you formulate a anything without knowing the ingredients.
Even when Emeril "bams" his gumbo the ingredients are listed on the label.
If your question is more generic, setting your advance with respect to rpm @ maximum torque is critical. Dyno numbers become important at that point.

"The plan is to light the charge in the cylinder with enough lead time (advance) to create maximum cylinder pressure at the ideal point after top dead center (ATDC) to push the piston down, exerting leverage on the crank. It's generally acknowledged that peak cylinder pressure needs to occur at roughly 15 to 18 degrees ATDC to maximize leverage on the crankshaft. If the spark timing is too early, the cylinder may experience detonation and potentially cause damage. Too late and un-burned fuel is flowing into the exhaust."

[911hutch]

Great simple explanation

[jpgroth]

Originally Posted by Dpmulvan

Looking for the best cam profile for present build.
3.0 small port heads
9:5 Je pistons
40mm carbs
Backroad driving mostly
Wondering what this M cam is all about.

I have a motor finishing up with similar specs. 3.0 big port, 9.5 JEs, 42mm ITBs and the M1 cam. Street car, can't wait to get back into the car

[PeteKz]

Henry, thanks for the continuing conversation. First question: Did you generate this chart based on your own data, or is it from an SAE paper or similar source?

The title: "Power v/s spark timing (at 1/2 throttle position)" raises several questions: Is throttle position measured as the throttle plate halfway open, that is, about 45 degrees to airflow? Or is it 1/2 MAP (about 7.3 PSIA)? I ask because 1/2 throttle plate open is pretty close to full MAP, especially at low RPM. So that influences how I interpret the rest of the chart. And, what does "v/s" mean? "Versus" or something else. I think you mean "versus, " abbreviated "vs."

Next, the chart labels the axes "power" and "spark timing" and plots two curves, one for single plug, and another for dual plugs from 25 to 40 degrees of advance.

I interpret a couple things from the chart. First, that a dual plug setup makes more power at lower advance than a single plug. Second, that as advance increases, the power difference between them converges. Now, at 40 degrees, I expect that to be the sum of the advance required for higher RPM and the advance for high manifold vacuum (low MAP), which generally indicates low engine load. But if the engine is operating at low load in that part of the chart, the power should have reduced, rather than turned up at higher advance or right side of the chart.

So this doesn't make sense to me.

How do you interpret it, and how do you use it to inform your engine building?

[PeteKz]

Henry, thanks for the continuing conversation. First question: Did you generate this chart based on your own data, or is it from an SAE paper or similar source?

The title: "Power v/s spark timing (at 1/2 throttle position)" raises several questions: Is throttle position measured as the throttle plate halfway open, that is, about 45 degrees to airflow? Or is it 1/2 MAP (about 7.3 PSIA)? I ask because 1/2 throttle plate open is pretty close to full MAP, especially at low RPM. So that influences how I interpret the rest of the chart. And, what does "v/s" mean? "Versus" or something else. I think you mean "versus, " abbreviated "vs."

Next, the chart labels the axes "power" and "spark timing" and plots two curves, one for single plug, and another for dual plugs from 25 to 40 degrees of advance.

I interpret a couple things from the chart. First, that a dual plug setup makes more power at lower advance than a single plug. Second, that as advice increases, the power difference between them converges. Now, at 40 degrees, I expect that to be the sum of the advance required for higher RPM and the advance for high manifold vacuum (low MAP), which generally indicates low engine load. But if the engine is operating at low load in the part of the chart, the power should have reduced, rather than turned up, at higher advance. This doesn't make sense to me.

How do you interpret it, and how do you use it to inform your engine building?

[Dpmulvan]

Talked to Henry this morning pleasant conversation very knowledgeable. He suggested Mod S cams or DC 30’s.

[Henry Schmidt]

Originally Posted by PeteKz

Henry, thanks for the continuing conversation. First question: Did you generate this chart based on your own data, or is it from an SAE paper or similar source?

The title: "Power v/s spark timing (at 1/2 throttle position)" raises several questions: Is throttle position measured as the throttle plate halfway open, that is, about 45 degrees to airflow? Or is it 1/2 MAP (about 7.3 PSIA)? I ask because 1/2 throttle plate open is pretty close to full MAP, especially at low RPM. So that influences how I interpret the rest of the chart. And, what does "v/s" mean? "Versus" or something else. I think you mean "versus, " abbreviated "vs."

Next, the chart labels the axes "power" and "spark timing" and plots two curves, one for single plug, and another for dual plugs from 25 to 40 degrees of advance.

I interpret a couple things from the chart. First, that a dual plug setup makes more power at lower advance than a single plug. Second, that as advance increases, the power difference between them converges. Now, at 40 degrees, I expect that to be the sum of the advance required for higher RPM and the advance for high manifold vacuum (low MAP), which generally indicates low engine load. But if the engine is operating at low load in that part of the chart, the power should have reduced, rather than turned up at higher advance or right side of the chart.

So this doesn't make sense to me.

How do you interpret it, and how do you use it to inform your engine building?

I posted the chart I had in a file marked race programs, not certain where it came from. You asked why we went twin plug. Complete fuel burn was the answer. Your question is way over my head. I'm an engine builder not a design engineer. I think you're looking for theory and it's not my thing, sorry.
Engine development is a art unto itself. Neil might be the place to go for the theoretical.

[Henry Schmidt]

Originally Posted by Dpmulvan

Talked to Henry this morning pleasant conversation very knowledgeable. He suggested Mod S cams or DC 30’s.

I just found a fresh set of 49 mm DC30 cams on the self. When you're ready, I can make you a deal.

[Dpmulvan]

Originally Posted by Henry Schmidt

I just found a fresh set of 49 mm DC30 cams on the self. When you're ready, I can make you a deal.

sounds good I’ll call you in the morning tomorrow.

[blue911rsr]

So what’s the difference between a regular cam and a modern cam?
Isn’t a cam all about making the most out of a given engine . Is the modern cam
going to give more power or what am I missing ?

[Henry Schmidt]

Originally Posted by blue911rsr

So what’s the difference between a regular cam and a modern cam?
Isn’t a cam all about making the most out of a given engine . Is the modern cam
going to give more power or what am I missing ?

Generally speaking, early 911 cams were low lift high duration. This allowed for low pressure valve springs.
This formula was an attempt to reduce valve train parasitic loss do to high friction. As a result, early 911 cams seem to give up low end torque.
What might be considered a modern 911 cam has a formula more in line with most conventional cam designs. Higher lift, shorter duration. This tends to produce better low end numbers but with most examples, you need higher valve spring rates. Now we start revisiting the higher friction issues. Friction means heat, wear and changing spring pressures means changing spring harmonics. It's all a dance to produce a desired result with the least compromise.
This old 911 design has a compromise at every turn and when people like Neal look to design things like "new" cams, reducing these compromises is the goal.

BTW: making the most power is a racer's mentality. Cams design is really about finding the compromise that makes for the best driving experience. An 8000 rpm 911 is a cool short term blast but a miserable thing to drive on an extended highway trip. Small displacement/high RPM cars are frantic to drive. Shifting mistakes [$$$$] become the norm. To best thing about modern cars is crazy performance without hysterics.

[Neil Harvey]

Originally Posted by blue911rsr

So what’s the difference between a regular cam and a modern cam?
Isn’t a cam all about making the most out of a given engine . Is the modern cam
going to give more power or what am I missing ?

The term "modern" should be considered when talking Porsche 911, just modern to the air cooled world not to the cam world.

Most of the cam profiles sold in the 911 world are all based on what was deigned back in the 50's and 60's by Harvey Crane. Porsche did not sell upgraded cam designs so many of the profiles offered for other engines in the aftermarket, we looked at copied and used in the 911 world.

Copies of copies etc., etc, have been sold for years to the 911 world. For many that is ok and everything they want. Many do not want to go out on a limb and try something new. We are all like that in our lives.

I have no problems with that. But our DNA is to create and design new parts for any engine we get involved in. We did this years ago for the air cooled world. Then the water engines came along and we focused on them. Cranks, Rods, Pistons, Cams etc, including the solution for the 991.1 finger follower issue.

Then a few years ago we were asked by several companies around the world to look at the 911 air cooled engine again. We looked at what was offered and saw areas we could improve. We redesigned our original Head studs, case through bolts, and looked at the camshaft selection that is currently offered. There was an opportunity to offer profiles that help control the valve motions a lot better.

We have learned a lot about valve motions since the 60's. Much of it has never been applied to the 911 world. Materials, coatings, Springs and weight have all come along way. So we decided if we were going to get back into the 911 camshaft aftermarket we would offer valve motions that were current. All of our new designs are Asymmetrical where needed and some are still symmetrical but these designs are improved versions of our older profiles. Demand on them would not warrant spending the time and investment on Asymmetrical valve motions.

The factory 964 is a classic example of how far behind 911 valve motions are. The 964 is a profile out since the mid 80's and still appears to be better than a lot of what is still offered today.

This new stuff is not for all. Some are happy with what they have and what is offered. What is the real shame, we are not the "cam business". Those that are should be the ones leading the way.

[Henry Schmidt]

I understand that My Pillow comes in a 2.0 model. Innovation is good, sometimes "new" is just a marketing ploy.
Neil is trying and should be commended but sometimes Bronzonium is just Bronze.

[Helix8]

And if you are not the lead dog the view never changes.

[Henry Schmidt]

Originally Posted by Helix8

And if you are not the lead dog the view never changes.

A Common Sense Approach to Meaningful Leadership

[Neil Harvey]

Originally Posted by Henry Schmidt

I understand that My Pillow comes in a 2.0 model. Innovation is good, sometimes "new" is just a marketing ploy.
Neil is trying and should be commended but sometimes Bronzonium is just Bronze.

You are right.

Like the lip stick on a pig theory. But I will keep trying.