A head design I was thinking of, and why it won't work

[Billzilla]

It's often brought up how 'twin-cam heads are very big, much bigger than a rocker head', and people are correct.
But are they?
I can a think about it and when you have a look at it, the cam-on-bucket system is a bit taller than a rocker-type but not a huge amount - the different is really not so much the valve actuation but the way the head itself flows air. Multi-valve heads are usually always a tumble & dump style and those have the inlet port coming down onto the valve at as very steep angle as possible and this is what makes the head 'tall'.
If you have a look at a cross-section of a Toyota head you can see how steep that angle is ->



Some of the older heads had more horizontal ports, like an earlier version of the same engine ->



But with a tumble & dump type port, basically the steeper the port the better the airflow ..... so the good heads really are quite tall.

The other type, the swirl port, are much more compact vertically as they don't come down onto the inlet valve at much of a vertical angle, but more sideways to get the airflow to swirl around the inlet valve, like this LS7 head ->



By using a swirl port is allows the head to be quite a bit shorter, and you again pick up a little bit with the more compact valve gear.

Anyway, I got to thinking and wondered if you could make a multi-valve head a full-on swirl type, to make it more compact. You'd get a lot of valve area for good breathing, a good-shaped chamber for good combustion, and the simplicity of cam-on-bucket all in a fairly compact head.
To do this, instead of siamesing the bifurcated ports from each inlet valve you'd have to spread them apart and so the inlet ports between each cylinder would be paired. So far, pretty neat. But then the cylinders at the end would have a single port for the inlet valve at the end. So for a four-cylinder head (4-pot of half a V8) you'd effectively end up with three large ports in the middle and two smaller ones at the ends .... not so neat but certainly not impossible.
I drew this rough diagram last night ->


(just drew the inlet side)

There'd be problems with interference from the inlet pulses in one cylinder affecting the neighbour one, but Chevys have lived with that for decades so that's liveable.

The side vew is pretty rough 'cause I'm crap at drawing stuff on a graphics program but you should get the idea.



(Again just drew the inlet side, and the port should be a bit shorter)

So it's looking fairly compact now and can still breath pretty well.

The problem is this though .... With the way the swirl works, it'd blow the mixture away from the spark plug and up against the cylinder wall. There'd be big problems with getting the thing to fire properly at increasing revs.
Direct injection would probably help, but I don't know enough about it.
Anyway, that's what I've been wasting a few brain CPU cycles on.

[mattysshop]

have you seen a 2ZZ-GE port?

the ports are just massive oval tunnels that show the back of the valve!

[oldeskewltoy]

Bill.......... What about mixing tumble with swirl. That way you could position the ports vertically??????


Yes - I realize this doesn't minimize any size... just a brainfart.........