400i vs. 412 Engine Block/Heads

I would not expect that a 200 cc/12 cubic inch increase in displacement would add more than 10 to 12 horsepower. But the increase in compression ratio from 8.8:1 to 9.6:1 could very well account for the rest of the 412's increase of 25 hp over the 400.

Also, consider this: that increasing displacement by 12 cc per cylinder might be enough to boost the compression from 8.8 to 9.6 all by itself. Assuming a flat top piston, compression ratio = volume of the cylinder (1/2 bore x 1/2 bore x stroke x 3.142) + volume of compressed head gasket + volume of combustion chamber, divided by volume of head gasket + combustion chamber. The 12 cc increase in displacement goes in the numerator, while the head gasket and combustion chamber volumes stay the same. The larger numerator results in a larger quotient.

If the 400 uses a dished piston, going to a smaller dish or a flat top will also boost compression.

To my way of thinking, horsepower is a measurement of an engine's ability to make torque at high rpm. Cylinder pressure is what makes torque. Starting out with higher cylinder pressure, prior to combustion -- through increased compression ratio or through supercharging -- results in higher cylinder pressure during combustion.

So what I'm saying is that a simple increase in displacement, without anything more, could add 25 hp. Better breathing heads would have an even greater impact, but 12 extra cubes and a 0.8 point increase in CR could do it without more.

P.S. About that exhaust system back pressure, I already mentioned in the thread about the 400's header pipe "horns" that this is misconception. I just Googled "exhaust back pressure myth" and got a bunch of hits. Here is one source that seems to get a lot of citations: http://www.thumpertalk.com/topic/571594-exhaust-backpressure-the-myth/

 

After I posted the previous post, I realized that, if we assume a flat top piston, we can calculate the volume of the combustion chamber and head gasket for the 400 and 412 by working backwards from the known quantities: displacement and CR. For the displacement volumes I used the figures provided by http://www.ferrari400.com/History.aspx .

For the 400, if "N" represents the combustion chamber volume plus the compressed head gasket volume, CR is 8.8, and cylinder displacement is 400 cc, the formula is 8.8 = (401.93 + N)/N. Solving for N gives us 51.53 cc.

For the 412, the formula is 9.6 = (411.93 + N)/N. N = 47.90 cc.

The 3.63 cc difference between the 400 and the 412 indicates that either the 412 heads have a smaller volume, or the pistons are different.

Here's a really good article about exhaust theory from the American hot rod magazine Popular Hot Rodding: http://www.popularhotrodding.com/enginemasters/articles/hardcore/0505em_exh/viewall.html . The author David Vizard is on the faculty of a university in North Carolina, whose name escapes me.

 

Our engines use a true hemispherical combustion chamber. The pistons are domed to fit into the combustion chambers. When I say a true hemispherical it is in comparison to semi hemispherical chambers like is used on Chrysler products.

 

"We all know" ? -not so sure.
The HP from these engines is pretty much present from approx 5000rpm and up to redline.
Dyno pic below is from my stock -77, carburetted 400 Auto, original SS exhaust system.

Enzo's words "Torque wins races" is easy to understand when you study the red torque curve.
These cars/engines are amazing when well maintained

Harald
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Does anyone know if the 365/400/412 engine is derived from the Lampredi engine? Were the heads redesigned to use side draught carburettors?

 

I'm not knowing what is meant by "Lampredi engine." But what I've read about the 365 GTC/4 engine is that the bean counters wanted to use a wet sump oiling system to save a few lira, that the taller wet sump oil pan combined with the intake ports and carburetors in the engine valley would make the engine too tall, and that the solution was to route the intake ports between the camshafts and use side draft carbs. That's the legend, anyway.

 

the two 365 motors I am having rebuilt will have higher compression pistons. at this point I am not sure what it will be. will find out