Italian V8 vs American V8- the Difference?

Displaccement and redline

 

Crank

 

The same difference between Latin women and American women--one exudes passion, requires finesse, and is always a mystery; the other, well if you have to ask...

 

Ferrari:
Moderate bore
Short stroke (although this has crept up in modern times to get more displacement/torque)
Minimal valve train inertia (overhead cams)
Alternate-bank-firing (this is the "crank" thing)

US:
Large bore
Long stroke
Pushrods (no real need to minimize the inertia since RPM is already limit by the two factors above)
Non-alternate bank firing

 

Ferraris have always had relatively small displacement engines. When you think about it, Ferrari was using 3.0L V8's when all the American muscle cars were 5.0L and up. Even today with high displacement Viper and Corvette engines the Ferraris are small (the 360 is still under 4.0L). This in turn promotes higher reving engines. For example the carb'd 308's redline at 7750rpms and with a bit of tweeking can go even higher. Ferraris love being in that high rpm range also. I find I'm always shifting up in the rpm band....it just comes alive up there. It's not how much you've got but how you use it.

 

I agree with 91TR

The American philosophy has been primarily to make power thru displacement while the Italian philiosophy has been to get it through efficiency.

For for the layman the difference is clearly in the sound with the American V8s all sounding very woofly while the Italians sounding high strung.

 

I know what you mean, But isn't it weird that a new corvette with 400hp and 400lbs torque gets 28 mpg and the smaller engine less hp and torque Ferrari 360 only gets 16 mpg. Not very efficient, Don't get it, but its true.

 

Had a 454-450hp LS6 Chevelle, but it doesn't compare to the F1 sounds and propulsion of a 355 Ferrari. Do miss the lumpy v-8 idle, but love the urgent 1000 rpm idle of the twin 4 firing sequence of the Ferrari.

 

Yes, but the vette probably goes way super lean at cruise, with high gearing to keep rpms down "low". The Ferrari probably maintains a normal mixture at much higher revs. , which in turn probably gives it better response. I mean, does Ferrari really give a crap if thier car gets crummy mileage?

I remember when I was just starting to drive, a kid I knew got a brand new Olds 442 for graduation. He wound it up on the way home, and let her fly. I think the car went maybe 5 or 6 miles at whatever top speed it could do, and then promtly threw a rod through the block. Only because someone seen the moron was the dealer able to deny warranty.

One other reason Ferrari could get so much power from the 2 valve 308, was the hemispherical combustion chamber, which they lost when they went to 4 valves, which is also why the 2 valve keeps increasing power with more lift and duration in cam timing, and the 4 valves level off. Its just not that efficient of a combustion chamber. Its probably also why they now are continuing to increase displacement as there is no other option left short of forced induction, or higher engine speeds to increase power. Increasing displacement has always been the cheapest way to increase power, all things being equal.

Paul~

 

As far as I know, all Ferrari V8 motors are flat plane crank.

As far as I know, all Americani V8 motors are cross plane crank.

This has a massive bearing on the 'demeanour' of a motor.

T.

 

Don't mean to change the topic but your understanding of combustion chamber design as well as basic knowledge of otto cycle engines is incorrect.

 

The corvette is a 360 plus cubic inch engine and the Ferrari 360 is a 237 cubic inch engine. The hp numbers for the 360 vary depending on where you find them, but I've seen more that show over 425.

I doubt the Corvette makes 28 mpg when its making 400hp but I'd bet the wizards at GM spent a lot of time finding ways to get the car to deliver 28mpg during the mileage tests. The difference is that GM thinks mileage is important to their customers (and maybe it is) but I'd also bet Ferrari couldn't care less.

All that said, the new C6 is a lot of car for the money and it should be a huge seller for the General.

 

the brits invented the 4 valve heads, but the Japanese perfected it. Prior to Honda's great idea of lengthening the valve stem, thus making sure that the intake and exhaust ports were straighter, giving a huge increase in performance, the brits tried, and gave up on the 4 valve head. When Honda showed up at the Isle of Man in 1959 with 4 cylinder 4 valve 250s and 350s, the brits laughed, that is until they looked at the trap speeds.

The flat plain cranks, and the high reving 4 valve heads (however the 355 and the 360 have 5 valves, technology developed and pattened by Yamaha) make more power than equal sized 2 valve head designs because the port design is better, and the wedge shaped combustion chamber is either as efficient, or more efficient than the Hemi head design.

Argt

 

Well, I really dont believe I am incorrect IMHO. I beleive the one reason the 4 valve engines "can" make more power is simply because of better flow, which puts more volume into the combustion chamber. The turbo-supercharged 288 GTO, using virtually the same basic engine, was rated at 400 HP in production, while a normally aspirted 308 LM engine, which was obviously detuned from a full race capability standpoint with only 9.7:1 compression, made almost as much if not more. There seem to be many differing figures on its exact output, but 380 HP seems the most common figure. As I have personally seen N.A. 1500 cc engines knock out 200 HP in high states of tune ( 12:1 pistons and higher, heavy porting, racing cams with power bands above 10,000 ). It is my belief, that the N.A. 2 valve 308 engine should be possible to make approx 450 HP in a full race configuration at high RPM above 10,000, or about equal to a "normal" F-40. The difference is that the F-40 with forced induction could make the same power with high boost at a lower RPM and therefore would be more durable.

Now, I am aware that a GTO or F40 can produce far more horsepower at higher boost, but so can any engine thats supercharged. A 2.0 liter anything can easily exceed 400-500 HP with high boost. How long it can maintain it is another matter. Also, I would be very interested in seeing a dyno chart for a 328, 348, or 355, at WOT held in the 7000 RPM range. I would be surprised if its higher at that rpm than a 308 2 valve with euro cams, after you adjust for the increased displacement. The 4 valve head allows the engine to rev higher without risk of valve float. Higher RPM with higher flow rates is obviously going to make more power, and the combustion chamber difference probably equals out at that point.

Paul~

 

The kid with the Olds drove it right off the lot, right out onto the freeway, and right up to whatever it would do flat out until it blew.

 

We understand. But why wasn't it covered by the warranty?

 

I assume it was for not observing the proper break-in procedure.

 

The flat plane crank vs. cross plane crank argument is exactly why "American" and "Ferrari" V8s sound different. BMW's cross plane crank V8 sounds very American, while Volkswagen's W8 flat-plane-cranked engine sounds very Ferrari-ish. To my knowledge, the W8 is the only currently produced 8 cylinder non-Ferrari engine with a flat plane crank.

The type of crankshaft determines the firing order, which is the most important factor regarding engine sound. Undersquare/oversquare bore/stroke designs, overall displacement, and head design, and valvetrain are all secondary.

Because of this, V12s sound like I6s, V10s sound like I5s, and flat-plane V8s sound like I4s. The cross-plane nature of "American" V8s give them the signature sound that is actually more like 4 V-twin engines than anything else. Of course it sounds better when you have twice as many cylinders, but you'd be surprised to hear my Volvo idleing next to a Viper, they sound the same with the Viper just being a little louder.

 

For maximum or peak horse power there is very little difference between a good two valve and a good four valve head. However except in drag racing a power band of some width is required. Four valve technology has been recognized for decades as being superior for that goal. Yes you can increase lift and with two big valves in a say 5 liter V8 that means something on the order of .600 to .800 inch. The stress on the valve train at those lifts is incredible and valve train components don't last long under those conditions. Then there is duration. To increase duration significantly you have to run lots of overlap. That reduces drivability, and width of power band. And oh, the other problem, exhaust emmissions go through the roof. Then last but not least the true problem with the hemi head. Every auto builder, emmission lab and racing engine developer in the world has come to agreement on this, Combustion Efficiency. The pent roof chamber burns better, the hemi is very efficent at breathing but not burning. The real advantages of the pent roof 4 valve chamber in addition to burning is that with more smaller valves the valves dont have to open as far (maximum lift required for maximum breathing is a function of several factors but is in the end controlled by valve diameter, so lifting a 1.25 inch valve .700 is pointless) reducing stresses and reducing the need for very stiff power robbing springs, but now for the best part. Flow at maximum lift can be equal in both 2 and 4 valve heads, however as long as we are still using camshafts to open and close valves a valve is only all the way open for a very short portion of its duration. The vast majority of the time it is at partial lift, and at partial lift the breathing capacity is limited by # of valves x lift x circumference, not diameter. With this equation a 4 valve beats a 2 valve big time. The best part of this last characteristic is that large amounts of overlap are not required for great breathing, improving overall power band and and improving emmissions.

As you stated a forced induction motor is not a very good way to judge, all you have to do is add force and you add horsepower. But if you look to the racing series where rules do not regulate this part of engine design, money is almost no object, forced induction is not allowed, that would be formula one. In F1 4 valves rule the day and I don't think they are stuck in 4 valve hell because that bunch of good ol boys aren't quite sure how to design a proper motor.

It is almost certain that something will push the pent roof out of the way, but it is almost as certain that it will not be the 2 valve hemi.


If I remember correctly it was that Honda 250 that made Mike the Bike a household name.

 

Sorry to do the hijacking, and the sound, yea the crank has a great deal to do with it.

 

Okay, I was just looking at a dyno chart on a 355. Looks like about 300 RWHP at 7000rpm, so about 350 HP at crank? coverted down in displacement to 3.0 liters would be about 255 RWHP, or about 300 at the crank, give or take. But at 6750 rpm, which is more where a stock euro 308 peaked, the 355 was at 270 RWHP, or about 231 corrected to 3.0 liters, or about 270 at the flywheel. Not a lot different from a 2 valve.

If a 308 GT4 LM engine made 380 HP at the crank, as most seem to feel, increasing displacement to 3.5 liters, all things being equal, should have around 440 HP, with about 360 RWHP. Am I way off here?? I still think the 2 valve engine has more capability of making more power N.A. than a 4 valve. Any 450 HP normally aspirated 355's out there? 430 HP N.A. 348's? 400 HP N.A. 328's? Of course, we arent really talking a great street engine with those P6 cams either.

But from all the different threads ive read, the 4 valve and 5 valve engines dont respond well to camshaft changes, they seem to just flatten out with no more increases in power, while the 2 valve continues to increase as the cam becomes wilder and wilder. The only possible difference that could account for that is the combustion chamber itself.