Do you mean the capacity to fill the cylinders? In which case it must do as the gases have to cope with the edge of the combustion chamber. Cylinder head fow modifications will include unshrouding the valves, thus changing the shape.

 

Yes.

For instance think about the valves, they sit in a recessed chamber, and they have one edge of the chamber up against one side of the valve, the other side is much more open. So the valve will flow more on the open side (towards the centre of the chamber) than the restricted side.

If you take a set of standard heads out to a larger bore, you can cut the side of the chamber back to give more breathing room round the tight side of the valve, allowing it to flow more.

So chamber design does influence gas flow.

Dave.

 

Yes.

For instance think about the valves, they sit in a recessed chamber, and they have one edge of the chamber up against one side of the valve, the other side is much more open. So the valve will flow more on the open side (towards the centre of the chamber) than the restricted side.

If you take a set of standard heads out to a larger bore, you can cut the side of the chamber back to give more breathing room round the tight side of the valve, allowing it to flow more.

So chamber design does influence gas flow.

Dave.

That's one of the reasons why big bore VW engines usually have higher outputs that stroker VW engines

 

Absolutely - it is the scientific/black art/Holy Grail of engine design.

Cheers, Carl.

 

I had an inckling that this was going the way of 'which head design is best for CFM?' that is opening a huge subject area.

 

Thanks guys.

The reason I asked the question is I purchased a pair of CB Ultra Mag Plus heads last year but with Mini Wedge Port chambers (as recommended by CB).
Looking at the CB CFM head flow spec's on their website the Mini Wedge Ports flow more than the Ultra Mags but I just wondered if having Mini Wedge Port chambers would the Ultra Mags flow a little better with this modification.

 

A little more application and build spec. would be helpful.

Cheers, Carl.

 

You own the heads - why not just install and go?

 

It's a road going 1303S.

Engine parts are for 2276cc fk10 cam, 1.4 rockers
CB CNC Ultra Mag Plus 42 x 37 heads, big beef manifolds, Weber IDF's 48's and CSP 42mm exhaust

cheers
Dean