Cylinder Heads

[m in sc]

Post below to id and discuss cylinder heads (including reshaping).

[Czakky]

Hopefully a noob question is cool here...

So on an air cooled RD a guy has a perfectly jetted bike. You throw on the most badass known to man heads. Combustion chambers are equal etc.
My understanding is that aftermarket heads also provide additional cooling at their best.

Are you really going to be able to lean it out significantly? Street application? Race bike application?

[Yamaha 179]

You will need to get more info from the experts but I've been talking to Kevin Cameron about engine tuning for some time and he says the current trend is not to raise the exhaust port as much as was common in the past and to increase compression.  This combination reduces the heat introduced to the piston but retains or increases power.  He said the squish clearance was in the neighborhood of .028" but did not suggest a compression ratio.  He also mentioned that the auxiliary transfers in my cylinder (I sent him one to examine) should have the rear wall re-angled to direct the charge more toward the exhaust port. 

He mentioned to me in the past that it might be helpful to make a shield or a guide to direct air over the head of our RDs to help cool the engines.  Probably not necessary for street riding but we road race them.

I suggest you contact one of the noted tuners for info on compression/porting/ignition.  It costs money up front but saves it in the end.
Lyn Garland

[rodneya]

Be great if somebody would make heads like this for the RD. These are for a RXZ by some place called Nasty Port Flow in Malaysia

[Czakky]

That's some pretty esteemed company Lyn! Interesting stuff. What is the max height you guys go with on exhaust ports now?

Those heads are crazy rodenya.

[Yamaha 179]

That's some pretty esteemed company Lyn! Interesting stuff. What is the max height you guys go with on exhaust ports now?

I need to do some research on the exhaust port timing.  The RD 250 cylinders (2R8 European) The Exhaust opens 26mm (81*) ATDC and is 38mm wide.  The Transfers open 41.5mm (116*) ATDC.  Boost Port is 20mm wide and opens same as the Transfers. Combustion chamber capacity is 10.4cc which yields a corrected compression ratio of 6.8:1.
   
I haven't looked at the RD 400 specs in a long time and need to dig them out.  Some I found from 2015 show ExO at 30.5mm (81*)
ATDC, TO/BP O at 47mm (114*).  No info on compression ratio.

Those heads are crazy rodenya.

Look like the replaceable combustion chambers we use in the TZs.  Don't know how well they would transfer heat in an air cooled machine.  Maybe OK??
Lyn

[rodneya]

Looks like there is quite a bit of surface area between the domes and head. As long as the dome is a tight fit heat transfer should be fine.
Get them clear anodized and they would look sweet.

[m in sc]

webco reproduction /improved heads RPRD 'brand'





cranking psi 150 on an aggressively ported aircooled 350.



limited production on these, were available 350 and 400. made in usa only . pics are 'as out of box' with no secondary work done. torroidal combustion chamber. take long reach plugs. (e series)

[EE]

Ralph Ponce  ralphponce65@hotmail.com  is the man behind the heads Mark referred to above as the "webco reproduction /improved heads RPRD 'brand' heads. Ralphs heads real brand name are "Superior Performance Heads"
The idea was simple, Tom Turner told me about RD350 heads made by Webco years ago along with the simple comment "great heads but they never made them for the RD400" (meaning they were about a 1/2" narrower than RD400 cylinder heads) and nothing came of it until i was building an especially wicked RD350 Roadracing engine for Ralph and he asked about heads and i ran down all the options along with modifying some webco heads with more modern combustion chambers and o-rings ect and mentioned that it would be nice if someone remade the heads and made them available for all the RD's 250/350 and 400's with modern combustion chambers ect and that set Ralph on the quest to make Simply the best RD Cylinder heads ever made. I helped a bit and made sure he made them able to be machined to work on all RD250/350 and 400's (that means European too!) and put him in touch with Wobbly Wright to design all new toroidal combustion chambers for them. Ralph had them sand cast because it gives better heat dissipation than billet or extruded heads and used the webco fin design as well for that reason. This really was an epic undertaking for Ralph as he had to learn all the facets involved from design to casting, to machining!! much much much more than people really think is involved and he did it to a T even discovering a higher copper content Aluminum alloy NASCAR was using to take the heat dissipation up to another level.  Beautiful and beautifully designed heads, my hat is of to Ralph for all his work and he did indeed create "Simply the best RD Cylinder heads ever made". Ed

[sav0r]

For that machined head, you might be able to apply a thermal paste between the dome insert and the cooling section to improve heat transfer. It's a great looking design though perhaps not exactly period for an RD. The problem I see with a machined head is that there's just no money in it. Even if you round up 10 costumers at $500 a pair the billets alone are going to be $50 a pop, then you're looking at like 10 hours of machine time, setup, fixtures, programming, design, tooling, etc.. There's no way to make any money on that, and even if it's a passion project, you're massively in the hole from the get-go. For example, I spent 40 some hours in the design phases for my fathers GT750 engine. Had that been billable... But that head was not even remotely from scratch (though we discussed it) it would have been way more expensive.

[m in sc]

thanks for the clarification ed.  I was (as you know) aware of all that but didn't know how much info Ralph wanted out on the webs. Everybody involved, including your work and a few others (not me, I just somehow got in the 'loop' at the time) def did one heck of a job on the development.