Flat plane crank RV8

[mongoose]

Has this ever been done/attempted.I can't see why it couldn't be done,with a different crank and cam obviously.I just thought that if it would create real scavenging,then it's surprising if it hasn't been done really

[Boosted Ls1]

It's been done before but machined from billet so it's expensive.

Also, you can't get proper balancing with a flat plane crank but people do seem to rev them without their engines falling apart. I was going to rotate the journals on my crank patterns to enable a flat plane version to be produced but it's not viable unless I sell several castings.

Boosted.

[cymtriks]

Why bother?

A cross plane crank is smoother and can still make decent power.

There is nothing magical about a flat crank and it's relationship to power though you could argue, in extremis, that a flat one will rev a bit higher. The real difference is in the exhaust system. With a flat crank you treat each side as a four which makes for relatively easy exhaust packaging. With a cross plane crank you can still get a high power exhaust system. In most cases the solution, which can produce good power, is to connect cylinders at 270 degrees apart which results in 1-3/2-4 on one side and 1-2/3-4 on the other side. The best layout, but very difficult to package, is to connect cylinders 180 degrees apart which results in cylinders 1 & 4 on one side being connected to cylinders 2 & 3 on the other side. The result is a complicated mass of curly pipework sometimes reffered to as a "snake pit" system. Check out the original Ford GT40 for an example.

Perhaps you'd be better off thinking about an exhaust system?

[jamieheasman]

Wasn't the Repco-Brabham V8 a Rover based-flat-plane-crank engine? Obviously in a single seater the desire to rev' and make lots of top-end power is more desireable than on a road engine.

I think I read somewhere that a company in America produce flat-plane cranks for Rover/Buick V8s - I'll check my 'favourites'.

[v8 racing]

we built a couple of flat plane rv8's years ago 91 i think the first one, but as mentioned earlier they dont make any more power without revving them so it still boiled down to the lack of flow that the heads could cope with, big big waste of money!!

[smac]

can you explain in idiots language how the crank is flat pane ( ie what it means)

Thanks

[Boosted Ls1]

Yes, when you look at it on a bench the journals are all on a horizontal plane ie flat, some to the left and some to the right, like a 4 cylinder crankshaft. Most v8 cranks are cruciform so end on they look like a cross.

Boosted.