Project 100hp rephased 880

[howardsmed]

And a dyno sheet to prove what exactly? No peeps on my end, I've proved my point years ago , do you think you're the only one who's digested the XS 650 head for extra flow that yielded positive gains? And besides, I was making a friendly comment to have a conversation with Christian, not you, so why are you being so defensive? This is one of the reasons I left this forum, people like you who get their feathers ruffled by misreading the context of the message. The work you've done is nothing new( but it's pretty porn) as I was doing it decades ago just never pushed it to your extent and went in another direction to achieve my personal goals in reconstructing the intake port and like you I was successful. Christian if you're reading this, glad to see you come back every now and then........Later

Hi Jack

On the 880 we raised the inlet port by around 6mm, Steve Mann who owned and raced the bike did the work, have you done the same ?
Steve machined the head ( and broke into the bottom of the spring pocket) and shrunk in a an aluminium tube,

I did something similar but far less elaborate on the SR500 head, it has sufficient casting thickness to lift the port + 6mm, and then weld the floor in ( see pic) i have access to a flow bench, a friend has an SF600 with data acquisition capabilities, and enormous knowledge ( albeit not on SR500, but Subaru turbo drag racers) have you done this ? and what are the gains?

I based the straight shot approach as per the Yamaha 5 valve engines where you can see the piston, looking down the carb or injector body, they flow well, and produce good power with very mild cams

we are 1/2 way into a 908cc engine with XV750 pistons and an 84mm stroke, will be nice to see how that goes

Howard

 

[Jack]

Hi Jack

On the 880 we raised the inlet port by around 6mm, Steve Mann who owned and raced the bike did the work, have you done the same ?
Steve machined the head ( and broke into the bottom of the spring pocket) and shrunk in a an aluminium tube,

Yes years ago I attempted raising the roof and floor of the XS intake port by 4mm but later on while flowing my welded-up closed chamber my good friend who has been porting for some 40 plus years and I discovered something trying to overcome shrouded losses of the welded up chamber. Pushed all my flow experiments to the side and concentrated on D - port the entire intake port while reducing port volume. The flow from 200 lift to 400 lift over exceeded my expectations and came on super hard to match the shell #1 cam lift. There's one D ported XS head somewhere in Germany, haven't heard from him in a while but he was extremely excited about the power increase and how it pulled through the RPM range.
Yes, I use to drag race back in the seventies racing Mopar 340s alongside an old gentleman who built and raced Ford flathead V8s and Mopars,who thought me areas to avoid porting the small block 340 heads.
Anyway, I just dropped by the forum to repay my respects to a dear friend of mine who passed away, not to cause a pissing contest, so I apologize for jacking your thread......Later

I did something similar but far less elaborate on the SR500 head, it has sufficient casting thickness to lift the port + 6mm, and then weld the floor in ( see pic) i have access to a flow bench, a friend has an SF600 with data acquisition capabilities, and enormous knowledge ( albeit not on SR500, but Subaru turbo drag racers) have you done this ? and what are the gains?

I based the straight shot approach as per the Yamaha 5 valve engines where you can see the piston, looking down the carb or injector body, they flow well, and produce good power with very mild cams

we are 1/2 way into a 908cc engine with XV750 pistons and an 84mm stroke, will be nice to see how that goes

Howard

 

[howardsmed]

Hi Jack

No worries, I had quite a few chats with Jerry Branch and Doug Coffey, Carl Morrow, ( who i used too work for in CA) about the shrouding caused by bathtub chambers, in the end the consensus was ( with HD and Buell's) that the increase in burn, and reduction in timing advance, with the attendant BMEP increase was worth the loss in flow.

Howard

 

[jpdevol]

Anyway, I just dropped by the forum to repay my respects to a dear friend of mine who passed away, not to cause a pissing contest, so I apologize for jacking your thread......Later

Please stick around sir - we have lots to learn from your posts

 

[Hudriwudri]

@all

For street bikes my philosophy is by now:
For street bikes D-port even perhaps with raised port floor
For race bikes heavy d-port with raised port floor.
For bad ass no expenses spared race bikes downdraft (quite some surgery involved) partially D-shaped intake port.

That is of course for now only valid for Sr/XT/TT engines.

Kind greetings and happy weekend

 

[Jack]

@all

For street bikes my philosophy is by now:
For street bikes D-port even perhaps with raised port floor
For race bikes heavy d-port with raised port floor.
For bad ass no expenses spared race bikes downdraft (quite some surgery involved) partially D-shaped intake port.

That is of course for now only valid for Sr/XT/TT engines.

Kind greetings and happy weekend

Some day when you get around to D porting that XS head, you'll be adding it to your valid list. When fully D ported and that head likes small port volumes to truly flex its flow and velocity muscle, you'll ask yourself why you waited so long to do it.

 

[Hudriwudri]

@Jack

Hi there old boy, i agree and looking forward to when (unfortunately also somewhat of a big but) but and that's a big buuuut, that of course one can lower the SSR velocity and enhance the flow and score on higher volumetric (with some tricks because the flow ain't just everything it's also what the mixture trajectory does after the port bowl )efficiency.
But and that's at least what my personal experience is on various ports with similar architecture (A65, commando, sporties, etc), on D-ports a majority of the flow passes on the Short side with very little flow on top, thus leading imho to: "in comparison to real downdraft ports" (used to work for a while a lot on serious 2v speedway stuff) less efficient chamber filling
Laminar flow shear in the port, even though the coeff discharge in comparison is "quite" higher.
All my rantings of course can not be generalized as it depends on valve angles, chamber shape and lots of other stuff that would go beyond a normal length post)
To cut it short, for my part i will definitely go on my build toward a D-port intake with most likely a filled in port floor.
For the rest of what I will need to do i will travel the bridge when I get there (sorry but I'm in backlog with several other projects and having a happy family that i cherish and try to dedicate sufficient time to), meaning i will investigate the ports on the flowbench with the usual tools of the trade (flo balls, prandtl tube etc) .

Straightening out a port helps a lot in:

Lowering turbulences
Going towards more homogenous (on purpose i don't utter the word laminar as it's not honey like consistence) flow one gains higher port flow with smaller cross area.

Sorry for my briefness today but I had ao g day today.

All the best and kind greetings z

 

[Jack]

I hope you realize I was just teasing you!

 

[Hudriwudri]

Hi Jack,

No worries at all.
As mentioned D-porting was already on my list for a long time as I'm a big fan of the work of Jerry branch, Cr Axtell, Kenny Augustine and all the other west coast boys (may they rest in peace and thanks a lot to their pioneering works)
No i did not notice but I was really tired yesterday evening besides that I'm already in my usual way somewhat a wacky spaced out kinda guy.
Most likely i would have explained (noticed today though unfortunately not as structured as i would have liked it to be) anyways to explain a hint to the readers the differences in port approach and port architecture without going into heavily technical lingo.

All the best and kind greetings

Christian