Intake manifold and port

hybridracer said:

I have had jobs for which I have signed the official secrets act and been vetted for national security. I have done work on projects that I won't tell anyone about. I respect other peoples intellectual property so will not give away drawings which do not belong to me. However, where there is information such as radii in inlet ports, or dimensions of camshaft lobes that I could measure from hardware, then I am happy to release that. Alas, having shared my office with Doug Hele, much of what I learned from him about the Domiracer I have forgotten as I foolishly did not write anything down. Some I have mentioned on these pages. For example - the actual cam lift diagram for the 1962 domiracer and that Doug NEVER called the domiracer frame the "lowboy"

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Surprised you’d even mention stuff like that…

TBW said:

Surprised you’d even mention stuff like that…

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Ancient history chum.

This reminds me of a discussion I had with an eastern European house painter re trout fishing lures.
He claimed to have made the perfect trout lure that the fish simply could not resist due to its special motion.

He explained
" Most trout lures just go this way" ( hand makes side to side motions)
Then his voice dropped to a barely audible whisper and he looked around to make sure no one else was listening in.
" My lure goes this way( side to side) AND..... this way!" (Up and down motions)
Of course after that buildup I was interested so I asked if I could buy one of these lures.
With his voice back to full strength he replied
" NO!!!
I HAVE SAID TOO MUCH ALREADY!"



 Glen

hybridracer said:

I have had jobs for which I have signed the official secrets act and been vetted for national security. I have done work on projects that I won't tell anyone about.

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Saying something about not saying something is saying only enough for us to know you're saying something about nothing, which is really something.

Ya can't bullshit a bullshitter.

In the meantime, the OP of this thread has started many threads, which are all more or less, disseminating and spreading his hard-earned IP, for us, a bunch of rank amateurs, fussing in our garages. One of the things he's posted is blueprint drawings of the SS head. These drawings and details are over 60 years old and were sold off to the highest bidder at the first opportunity. They couldn't have been that precious. The cats are all well out of the bag, and we're talking about all of them. It's an internet forum. It's what we do.

OK, that's telling me off. I was building up to a nice bit of H. G. Wells type science fiction but will stick to the topic of inlets.
To state the obvious, length and diameter of the inlet depends on how one intends to use the bike. I still contend that for everyday road use, the original, unmodified Commando was the best, or at least mine was. I don't know if the silencers I had, containing nothing but short stub pipes with 2 longitudinal slots in them, were standard or specific to the PR. Sorry, off topic again with the exhausts but as others have pointed out, if you alter one part of the power plant, the rest should also be considered.

"I am not an engineer, I am an industrial chemist. I have spent most of my life in engineering factories."


Any insight on this?

Another industrial chemist here! IIRC...The tanks Acerbis made for Triumph and Ducati were made of a Nylon material. This material tends to absorb fuel, especially E-10, which can make it difficult to mend with adhesives. I repaired a 955i Triumph tank with JB Weld and it held for about 2 years. From the looks of that Daytona tank, I'd soak that area with straight ethanol for awhile to remove gasoline, dry it well and fill that convenient cavity with JB. Alternatively, Nylon welds fairly well.
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Intake manifold and port. So, this is BSA again but to show the difference from std to modified shape without making the port larger, both enter at 30mm and the modified transitions to oval in the head and I tested with std 40.5mm valve then 42mm, bigger is better. Std port 109cfm, modified around 150cfm or a bit more with a smooth entry. The speed in this port was very high around 450fps the 30mm port was a serious restriction to CFM. As was a 30mm Concentric because disturbing the flow really blocked it up. Smooth bore carbs would help but they are basically too small at 30mm. The speed is high but the volume is not. I do not know how it would go on a bike because I have no decent 30mm carbs. Fighting for flow and then losing half the gain with a carb seems self-defeating.

But this is showing plugs from both these ports to compare, and how it is altered to flow more. Basically, not choked at the guide, that chocking is not a venturi but a blockage. From the side view the std port directs air across the valve using the top edge only. The modified port takes it up and turns it onto the back of the valve, and it runs smooth without bumps to cause turbulence and blocks. That front part of the port should flow 170-180cfm if the runner was not so small, but with a speed drop to around 400fps or a bit more.







This is an older head it's 34mm and the oval starts in the head and looking at other images I can see a couple of things not great and why it's a bit down on flow compared to what a few years stuffing about can now get. So, this is on a LSR bike in the states, another long stroke 750. It surprises me they go so well. It has only run the last two years with this head. The first year he raised the standing class record at that track by 30mph and last year he added another 10mph. What is dicey is the ridge up to the guide is sharp and the air will not particularly follow that, if it's a smooth lump without the fin the air is less able to rip off it. When you get all the cfm you can get, until you get more, you do not know you can, nor do you know exactly how.