Singles Breathing

[graeme]

I'll start this as it was started on the Desmo cam thread and some feel it should have its own thread.
I can only talk about 450 heads, as that's all I've played with.
None were for racing, just some performance more suited to what a 450cc can (should) be capable of.

a standard RT 450 head






another RT 450 head opened up
42mm inlet valve and standard 35mm exhaust valve







Anyone interested?

Graeme

[Jordan]

Hi Graeme,

Did you create a pocket on the upper part of the inlet port, just before the valve seat?
It looks that way, but could be just the photo.
Any reports yet, on performance difference?

I rode a ported 450D once. It was noticeably more powerful. It had a bigger carb too.

Jordan

[graeme]

Hi Jordan,
This was done 20 years ago and it's on my 450 road bike.
Yes it has an RT head on it. The original head was sold with an old race bike long ago.
It does have a slight pocket.
It has a 36mm dellorto which gave better performance than a 32 or 40.
The manifold is a straight item that I got from Road and Race a long time ago.
These were very long and suitable to cut down to suit.
Also my '74 450 is one of 3 I've had with a 250 frame so the 450 gusset doesn't interfere with the carb.
It goes very well by seat of the pants dyno.
The original RT head in the first pictures is on my RT. ( but it was not as much fun, so now it's been cleaned up and has a 32mm carb)

Graeme

[Jordan]

I read about the benefit of making a pocket, to deflect the charge downwards into the cylinder.
Is this standard practice on Ducati singles, with their rather flat inlet tracts?

Jordan

[Eldert]

improving the breathing doesnt always mean removing material . you can improve the flow by adding material
i had a very bad Mototrans cilinderhead witn no support around the exhaust valve seat .
removed the ex seat and had the reces for the seat and the bottom of the port filled in with weld



put in a smaller valve seat and a smaller ex valve ( 35 mm ) made a nice radius on the bottom of the port
this port flows way better than the original one



Eldert

[graeme]

Hello Eldert,
I've seen this done on the inlet but not on exhaust. The flow did increase considerably with a smaller port but better shape.






I have seen a Norton head with a "step" in the exhaust port, lifting the floor of the port up, before suddenly becoming full diamiter as the exhaust header is screwed on.

Greame

[Eldert]

here a picture of the exhaustport of my strongest 500 race engine
you have to weld . epoxy wont hold up . the exhaust runs way hotter then the intakeport



Eldert

[graeme]

Eldert, your exhaust port is the same as the commando heads port I have seen.
Can you explain why the shape suddenly changes at the header pipe, does it have something to do with vacuum in the port?
Graeme

[Eldert]

Hi Graeme

i tryed this portshape ( D on its side ) and its worked for my engine . that good enough for me .
other people use a torque valve at the start of the headerpipe

here a picture of the exhaust port of a Mototrans cilinderhead . as Nigel mentioned before there is no material
under the valve seat in some places .



Eldert

[MK III]

Eldert's photos are spot on for flowing the Ducati heads. My Brother Ed built a number of Duc single race bikes in the '80s and rode for/with and against Syd's Cycles race team. He also earned the #1 amateur plate in '84 aned '85. Jesse O'Brien - brother of Dick O'Brien who ran Harley Davidson's race engine development division - set up O'Brien Flowmetrics and did extensive work on the Ducati singles resulting in Syd's and my brother's extremely fast 250s 350s and 450s. Just out of interest, go to syd's cycles website, scroll down and there's a photo of everyone including Malcolm, Syd, brother Ed and Jesse along with a "Few" of the trophies taken at the time. Getting back to the current thread, here are several photos I've taken of the head that Jesse welded up and flowed for me back in the day. Exh port is filled to create a more rounded pathway, then the intake is also "rounded out" but with epoxy as its on the cool side of the engine. Intake valve is 42mm, exh valve 37mm. Bigger is not always better - shape is very important. Compare my pix to Eldert's - almost identical!
After a twenty five year "vacation" in two-stroke land I've just dug out all of my vintage singles stuff and am in the process of cleaning it all up. cataloging it and hope to build a real nice Mark 3 type street machine. Just had this particular head on my milling machine yesterday cleaning up some "stray" weld spatter.