Five Valves Per Cylinder

One of the things I miss about owning a 360 is the noise it makes, something which the F430 simply cannot compete with.  One of the main reasons for this is that the 360 (and F355) was made with five valves per cylinder – three on the intake and two on the exhaust.  This system was first adopted by Ferrari for their F1 engines before making it into a few road going cars.  There is a lot of incorrect information out on the internet about what the extra valve achieves so I hope to provide a short explanation about this system.

The three valves on the intake are the same size and are positioned in such away that they would each roughly let through an equal amount of air into the cylinder.  Here’s a picture of a failed inlet manifold gasket – you can just see the valves in the bottom right of the photo.

P1010256

So why use three small valves instead of two larger ones?  Well the difference is actually on the camshaft.  The middle lobe has a slightly different profile than the outer two, which means that the middle valve opens later.  The different profile can be seen in this picture – note how the middle lobe looks slightly lower than the other two.

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Now although he other side of the lobes are exactly the same – they are different which means that the central valve closes after the outer two.

DSC02894_

This arrangement means that the valve overlap is happening on a more restricted amount of intake airflow.  I can only suggest that Ferrari worked out that it was optimal to have the overlap happening with a smaller amount of air flowing into the engine.

Once the middle valve opens it produces a surge of air into the cylinder.  This in turn produces pulses in the air intake system which gives the 5 valved cars their distinctive noise.

So why weren’t the five valves carried forward into the F136 series of engines?  Well the 360 has, by today’s standards, a crude variable timing system on the exhaust cam which changes the amount of overlap between two fixed positions.  The newer V8 engine fitted to the F430 and it’s successors has continuous valve timing on all camshafts which means that overlap is much easier to control.  But progress comes at a cost and in this case it is the acoustics…

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4 thoughts on “Five Valves Per Cylinder

  1. As always great to read your stories weldone Aldous. However the biggest noise pleasure is coming tru the exhaust valves and its mainfold. The changes with from a standard to a Tubi is tremendous. Never heard that the air intake valves are having an influence on this noise.

    1. Thank you for the comment. I disagree, in fact quite a lot of the noise you hear from the cabin is made up of the intake.

      Changing the silencing does change the overall note, for the better in most cases!

  2. Just to add…

    1. The middle lobe opens later and closes earlier than the outer lobes.

    2. I can not say when or why, but i have a very early head and the inlet cam has all 3 lobes in-line.
    So clearly ferrari experimented with inline lobes and decided against it.
    Can only assume the middle ran to close to the piston, but when i measured it, there seemed plenty clearance.

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