What is the modern equivalent to a 906 cam?

[obrut]

The 906 cam is often described as an 'old fashioned' profile. Not that suprising given it was developed 40 or so years ago.

What would be the closest 'modern' (whatever that means) cam design to a 906 profile? Application is a 2.0 litre engine.

[Eagledriver]

The 906 was a very high RPM cam profile. It was also designed to keep valve accelerations to a level that was within valve spring capability of the day. A modern cam like the GE-100 would be for a similar RPM range but is superior. It is designed around racing valve springs and titanium retainers.

-Andy

[camgrinder]

A good replacement for the 906 is a DC60 profile. More torque and HP, and will still pull past 7600 rpm in a 2.0 litre. If you want 8k plus potential, go with a DC80. The DC100 (similar to the GE100) would be closer to the 3.0 RSR cam. I cant remember the last time I made the DC100 for a 2.8l or smaller engine.

[obrut]

Thanks guys.

John, you have PM.

[Henry Schmidt]

I would have tought that a DC 100 was closer to a Shrick cam from the old 2.5 IMSA days.
Just to refresh your memory, you made me a few sets of what we called a DC90 for a couple of 2.5 engines I built 2 or so years ago.

[obrut]

Thanks guys.

A buddy is using DC44 on 102 degree lobes in his 2.3. How would these compare?

[camgrinder]

Originally Posted by Henry Schmidt

I would have tought that a DC 100 was closer to a Shrick cam from the old 2.5 IMSA days.
Just to refresh your memory, you made me a few sets of what we called a DC90 for a couple of 2.5 engines I built 2 or so years ago.

That "IMSA" cam has even more duration than the 100 cams do.
It would be interesting to see a DC90 on a 98 lobe center in a 2.0 litre. With lots of compression.

[camgrinder]

Originally Posted by obrut

Thanks guys.

A buddy is using DC44 on 102 degree lobes in his 2.3. How would these compare?

The DC44 cam is in between the DC40 and the DC60. It has slightly less duration on the intake, but more lift on both sides vs. the DC60.

[Henry Schmidt]

Originally Posted by camgrinder

That "IMSA" cam has even more duration than the 100 cams do.
It would be interesting to see a DC90 on a 98 lobe center in a 2.0 litre. With lots of compression.

I wasn't talking/ referring to the Elgin IMSA cam That was a monster.
I was referring to the Shrick cam which I believe was the basis for the GE100.
You're the cam guy and I wouldn't doubt you for a second just something floating around in my cranium.

[camgrinder]

Got ya. I have a Schrick that checked out 272/260 @ .050" with .520"/.500" lift on a 98 lobe center.

[gestalt1]

i find it interesting that many think of the 906 as the race cam from porsche's past. what about the rsr sprint? it seems rather close to the ge60, wouldn't the sprint be the modern replacement for the 906? how would a sprint work on a small bore race engine?

[kenikh]

Originally Posted by obrut

Thanks guys.

A buddy is using DC44 on 102 degree lobes in his 2.3. How would these compare?

Cameron's cams were designed by John, for me, with the design criteria of making more torque, sooner than an 'S' cam, but with near 8000 RPM potential. Those cams make peak HP at 7800 RPM and are one of the best cams you can build for a small motor. If going to 8K, the ramps speeds require a lightened valve train.

I describe them as "hitting low like an 'E', then exploding high like a 906". While overstating it a bit, they were designed specifically to feel very E-like low in the RPM range and very 906-like high up. The specific target for the cams was just short of 100HP/L on CNC ported heads and taper bored MFI at shy 8K RPM.

My project changed directions and Cam was the beneficiary of my flighty way. That reminds me, I need to email him.

[kenikh]

Originally Posted by gestalt1

i find it interesting that many think of the 906 as the race cam from porsche's past. what about the rsr sprint? it seems rather close to the ge60, wouldn't the sprint be the modern replacement for the 906? how would a sprint work on a small bore race engine?

FWIW, the Sprint cam is more fun than a barrel of monkeys on a 2.8 short stroke. Makes this motor feel like a 2.2S on McGwire quality steroids, then just keeps pulling past 8K like no 'S' cammed car would dream. Best damned NA motor I have ever driven.

[kenikh]

Originally Posted by camgrinder

That "IMSA" cam has even more duration than the 100 cams do.
It would be interesting to see a DC90 on a 98 lobe center in a 2.0 litre. With lots of compression.

What's "lots"? Race gas only "lots" or pump gas "lots"? Twin plugs are assumed.

[Walt Fricke]

Kenik - you wrote:

"FWIW, the Sprint cam is more fun than a barrel of monkeys on a 2.8 short stroke. Makes this motor feel like a 2.2S on McGwire quality steroids, then just keeps pulling past 8K like no 'S' cammed car would dream. Best damned NA motor I have ever driven."

Is this the "RSR Sprint" cam?

The 2.8 SS I am slowly assembling (just got the heads back from twin plugging and valve guiding) will need a cam. I am hoping for ~12 CR, though with the valves I am using (51.5/42.5) I am going to have to recut the J&Es, which were designed for stock 3.2 sizes, and that will add volume). My plan is to shift at 8,000 rpm (for a little more bearing, spring, and valve longevity), which is apt to mean a HP peak of about 7,500 or so, and a torque curve to attain that (I'm going off of the shape of my current 2.7 race motor torque curve and transmission gearing, where 7,600 is the optimum shift point for a torque peak about 6,000 and a HP peak about 7,100).

My take is that moving the torque curve too far up means shifting at optimum will be higher than I want. And short shifting is apt to mean giving up something on the low end, given that you can't expect a torque curve to be flat from 3,000 rpm through 6,600 plus rpm, and with the cam you are sort of moving the curve around.

So the RSR sprint might be a bit too much. Do you have a torque curve for this in the 2.8 SS application you could share?

Walt

[kenikh]

Walt, you havr two major design concerns to accomodate in pursuit of your goal big (meaning heavy) valves and very high CR. The Sprint cam has nice, gradual ramps that will accomodate these heavy valves at high RPM, as well as lots of overlap to accomodate your high static CR, by lowering dynamic compression, especially at lower rpm.

Anything "less" in terms of overlap would gain low end torque, at the cost of running into major detonation problems due to elevated dynamic CR. Also with a more "modern" cam (with faster lobe ramps), you'd need at a minimum, titanium retainer and even possibly titanium valves to get a reliable 8K.

The Sprint cam in a 2.8SS makes more power low than you could imagine. When I said a 2.2S on steroids, I meant in terms of character. This motor makes way, way more power everywhere, from idle up than a 2.2S. It is a fantastic combo and is why Henry likes this cam so much in the 2.8SS. Also, the 2.8SS has gobs of displacement to overcome low RPM pumping losses from overlap that smaller motors just can't.

It is definitely NOT too much cam.

I am sure Henry has posted some dyno sheets on his Sprint cammed 2.8SS...see if you can find them in the engine rebuilding forum.

[gestalt1]

i brought up the rsr sprint because it seems to have less overlap than a 906, 101 vs 96 lobe center. should i assume that the duration is so long on a rsr that even though the lobe center is wider there is still a lot of overlap? i am thinking that the wider lobe center would help at lower rpms. do you think stock springs/valves and retainers would be ok with an rsr cam up to 7600 rpm?

[kenikh]

Originally Posted by gestalt1

i brought up the rsr sprint because it seems to have less overlap than a 906, 101 vs 96 lobe center. should i assume that the duration is so long on a rsr that even though the lobe center is wider there is still a lot of overlap? i am thinking that the wider lobe center would help at lower rpms. do you think stock springs/valves and retainers would be ok with an rsr cam up to 7600 rpm?

I have run an RSR cam on a 2.8SS to 8300 RPM with relative frequency. No issues, especially with Ti retainers.

[Henry Schmidt]

The magic to the RSR sprint cam is that it will function relatively well at all rpm ranges including idle with as little as 9.5:1 compression. This means you can run a twin plug engine to 8500rpm on street gas. This engine does just that.
Look to future issues of Excellence magazine for an article on the Red Sled

[kenikh]

I cannot wait!