Sorry, I jumped the gun. 6mm in a modern 4 valve head - I've used 7mm and 8mm stem valves in a 356 head. Saves a boatload of mass for sure.

So 133hp/l lasts 24 hours, how long do the 100hp/l motors last and are they running race fuel only?

That depends totally on engine CR and how hard its turned. :) :) Driver overrevs also play a big role here, too.

Race gas only, for sure.

I know its an old quote, but I'm interested in learning what the failure mode of these kinds of engines are..what is it that fails first/limits the motor to such short lifespans?

Thanks

In a galaxy far far away..............
I have to know the specs of an engine like this. An NA, two valve 3.0 Porsche engine producing 400hp sounds a little like a unicorn story.... With all due respect.

Can you say 9,000+ rpm, idles at 3500 and 13.5:1 CR?

Check this guy; A swedish pro on Porsche engines
SpezialMotorer-Engine Development

John JL - I'd be interested in knowing also.

With older, and I think somewhat milder, engines, maybe the rod bearings mostly?

But the Cup 996/997 engines seem to require replacement of a whole lot of stuff in addition - I hear the valves are beaten up beyond reasonable repair. And the seats, which also means the heads have to go because fixing them costs more than new heads. Doubtless a lot of other stuff - titanium rods cycled out?

I seem to remember a guy who raced a 914 4 cylinder in SCCA letter class racing. He had to put in a new crank every weekend or something, I think he said. Helped that he had a crank grinding business.

So what gets replaced on a hand grenade motor?

And what on a 2 valve roughly 100 hp/liter or 100 hour motor? Not the nice to replace stuff like chains and sprockets, but stuff which for sure will not last another 100 hours? 100 hours ought to get a guy through a racing season.

Yeah, look under "Projects" and there's a 418hp 3.2L N/A engine. :eek:

That horizontal fan on the main page will set you back about $30K I understand? Wow.....

Power: 418HP@7400 Torque: 341Lb ft(462Nm)@6000 ?

I caught a fish THIS BIG!

Very good analogy! :D

Cant see the problem its 130.6hp/litre at the crank.

He is one of Swedens best engine builders.I´m pretty shore that you have some guys in the US that kan match his figures.
The only problem is the bill that is THIS BIG!
There is no lack of skills and knowledge.I say his on the very edgeSmileWavy

418 hp @ 7400 from a two valve, hemi head, 60 year old design running on gasoline ????
I've done plenty of dyno runs looking for max numbers where a peak is achieved but not reproducible under driving conditions. Those numbers mean less than nothing.

I'm calling BS on that. That is more specific output than the GT3RS 4.0, which has the record for specific output in naturally aspirated production engines, greater than the 458 Ferrari even.

If that was accomplished with a turbocharger then it is not that surprising.

An interesting discussion, but cam and intake design are just the tip of a very big iceberg. Every motor is a compromise of some sort and some other questions probably need to be addressed as well:

What fuel will you run? 100hp/liter is easier to do with 100 octane than 91 octane. Are you considering a methanol blend?

How long do you want it to last? A drag racer can produce phenomenal hp for about 10 seconds, and then the crew rebuilds the top end in the pits between runs. A motor built to last through 24hr Le Mans will be quite different. A motor designed to go 100k miles will be different still. The more power you make, the more fragile a motor tends to be.

How will you eliminate excess heat generated with more power? Heat kills motors quick. Excess heat is also a barrier to hp as we have seen with top 993 race car motors.

How critical are you willing to tune it? A tune at the ragged edge will produce more power... just before it detonates and grenades. A carb is a relatively crude device requiring a wider tuning window compared to modern DFI and microprocessor controlled ignition.

How fine balanced is your rotating mass? The more balanced the motor, the higher your rpm safety margin.

Do you generate enough oil pressure at max power to safely float all your moving parts? If mechanical forces exceed oil float, pistons seize and crankshafts fail.

These are a few of the common questions that engine builders face when planning their next motor project, whether it be a street car on steroids, 1/4 mile car, or road circuit race car.

Just my 2cents towards the discussion. Carry on.

FYI,

The 418HP@7400 Torque: 341Lb ft(462Nm)@6000 motor needs a Volumetric Efficiency (VE) of about 125% to make those numbers N/A.

Steve's 3.0 making say 400 HP @ 9XXX RPM needs a VE of about 110%.

Henry's 3.0 making 310 HP @ 7260 needs a VE in the 112% range.

I wont say its not possible but it would be darn hard to squeeze out that 125% VE number from a 2 valve per cylinder air cooled motor.

I will say Steve did his back in the day, no thermal coatings, no oil shedding coatings, no CNC heads not even sure he had a flow bench back then. I believe it was lots of dyno time backed with track time.

Henry clearly hit a home run on his combination, not sure what modern tweaks he may have used to get there.

As for how long any of these motors will live I believe high RPM is the #1 reason for short service intervals, the #2 reason heat.

What is the maximum VE achieble with a porsche ground design according to you?
What rpm is best suited too accive highest possible VE?
Too accive big VE numbers you build the engine around the camshaft (propably his design) and not the other way around.
Normal well reputaited enginebuliders (no names) how much will they alter in engine design (portsize, pipelength/diameter on inlet and exhaust etc) when taking this or that camshaft?
110% VE is a number that every skilld builder will see using well proven recipes and good craftmanchip.
All engines he build is about tourqe (VE) hp at low rpms.
He´s not a ordinary Pipemax design chap his far beyond.

I agree with you that whp is the messurment thats most correkt (real life), but engine braked hp is still valid.
Have never seen him bad mouthed by anyone who have had engine built there.Engines deliver expekted performance.

Happy ChristmasSmileWavy

Let's take this one step further.....

The 417 HP motor at low RPM makes 1.873 Pound / Feet TQ per cubic inch and 2.296 HP / cubic inch.

The winner of the Engine Masters challenge last year, with a 2 valve Hemi V8 low RPM deal made 1.489 Pound / Feet TQ per cubic inch and 1.67 HP / cubic inch.

A 350 cubic inch NASCAR V8 makes about 2.28 HP / cubic inch at 9000 RPM.

So this engine is making a bit more power per cubic inch than a NASCAR V8 and would have dominated the Engine Masters Challenge. That is a stout piece.

Not impossible just higher output than I have ever heard of in a NA Porsche. I would love to see the build spec for it as I am sure it is a very well matched motor.

That was done with a LOT of flow bench time, followed by hours on the dyno. :) :)

Pistons take a royal beating in high RPM race engines and that's just one of the components that gets replaced every 25-50 hours, depending on the configuration.

The more compression you run, the higher the operating RPM, the more often it needs to be refreshed. Typically, sprint engines do not last anywhere as long as endurance engines due to these main variables.

Currently, we are seeing 430+ BHP with 326 lbs-ft on some large-displacement sprint motors under development.

First av all i will say 2.28hp/cubic inch from a nascar engine is amasing with a 50-s design pushrod, oddfiring engine that I asume have some restiktors/rules that limits outpot further:cool:
If we are doing the math a standard 3.2 is 193 + cubic inches.
418hp/193=2.16hp/cubik inch witch is ruffly 5% less than the NASCAR engine(at much lower engine speed 7400 rpm).
341Lb ft/193=1.77Lb ft/cibic inch is ruffly 5% higher then Mega Cubic Monsters.
IF you look at the rules for Engine Mastes Challenge only engines of 400+cubic inches allowed and a lot of restrikting rules too med and goal is the highest total output HP an Tourqe wise.Not get the highest lbf/cubic inch possible.
These engines are still oddfire no individual trottle bodies etc witch is´t a benefit too ashive highest possible VE.
Happy ChristmanSmileWavy