No prob, look forward to hearing how she does.

That cam you are using is one super-hot cam. My experience is in the Ferrari world, and I call that cam a 100% racing only cam. Even the 512BB LM flat 12s don't use a cam quite that hot. IIRC, the 512BB LM runs 270 @ .050 intake duration which yields 530bhp at nearly 8k. I have a dyno sheet for it somewhere. I believe the 906 engines use something a little hotter even then yours? Something like 282 @ .050.

Regardless, if you wanted to make it a race fuel only engine I wouldn't change the cam. Bump static compression to 12.5:1 or 13:1 and you will have one serious racing engine.

Do not be upset if your engine is dyno'd and you find the low end of the engine to have only a few more bhp if that. The high end is what this cam is all about. Luckily your lobe center is such that you will have lowered the torque band somewhat. Ahhh to have a 4 cam Ferrari engine we could really mess with seperation angles and power bands!

In looking around it looks to me (not an expert) as though it is similar to the 3.0RSR Sprint cam.

This is a race only engine so we'll see how things go. I'm actually trying to keep the hp down somewhat to fit into a specific race class. I'll definitely be running 110 on the dyno just to prevent any octane related issues.

I ended up finding some dynamic compression calculators and the most difficult thing was trying to come up with the value that the intake valve closes. Do you have a formula using the information I provided? If so, could you post the math?

I used a few different methods and came in with 60 ABDC and 68 ABDC. I was probably doing something wrong. Either way the maximum dynamic compression these calculators came up with was 9:1.

I agree with what has already been discussed. NC and SE summers in general are brutal and you will be pulling timing advance to keep the engine safe. Better to go with lower compression and maintain optimal timing.


I would personally run a stand alone knock sensor. You may not need to having timing feedback but wiring the output to a big, bright LED or other indicator on the dash could allow you to notice the subtle hints before the big bang.

J&S comes to mind.

Here is another simple solution that is basically a frequency filter circuit attached to a knock sensor. I would think that mounting to the base of the CIS console stud would be be an option for LEft bank, cyl #3. It is not optimal compared to cylinder or head mounted devices but could be better than nothing.

Engine knock detection and indication for all vehicles

I take the intake closing figure @ .050 and add 15 degrees which gave me 75 IIRC. The rod length (5.031") and stroke then calculate the effective stroke.

You have to remember that the cam you are using is going to truly be optimal with better part of 12.5:1 to 13.5:1 compression. They way you have it now with 11.3:1 will be fine all around. With an effective stroke of less than 2 inches, you are really going to be spinning this thing. If you had any less of a cam you would be running into issues with your static compression ratio.

By my calcs, this cam, with static CR of 11.3:1 and guessing at a 101 degree lobe spacing (RSR Sprint cam) gets a dynamic compression ratio (at rest) of:

7.85:1

This is in comparison to:
RSR Sprint cam: 6.43:1
906: 6.27:1

This is still lower than a 12.5:1 static CR, 906 cammed HSR racer, which results in a DCR of:

8.68:1

So this motor, which will be used in anger similarly to these other race cams (and thus assuming similar VE and cylinder charging characteristics at speed) is a full 2 points higher in at-rest DCR than Factory racers, but one point lower than rebuild-after-every-race HSR motors.

Sounds like race gas is more than in order.

That's it, I was not adding 15 to my numbers.

Great comparison info. I agree completely. Thank you for putting it in those practical and relative terms.

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My '76 Ferrari 308 runs 7.7:1 dynamic compression and is stock. The quench is not very good for this engine so I can run about 39.5 degrees total timing. Pump gas is fine. It's when one get above 8.3-8.5:1 (depending on efficiency) that race fuel is absolutely needed

Yes I considered this approach. The J and S unit looks really nice. I came back to the point that if I just feed this thing the proper fuel, detonation will not be a problem. The engine is in a race car. I don't know what I would gain by trying to run minimum octane with knock protection. For my application I think there are lots of advantages to running race fuel. Buying insurance a gallon at a time.