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Head flow testing.

Classic Norton Commando Motorcycles.

Re: Head flow testing.

Postby WZ507 » Wed Mar 02, 2016 8:24 am

Snotzo,

As is so often the case, thank you for allowing us to see what we always see but think what some of us (me) have never thought. With respect to your comments about the fifth lift point (valve lift = 25% of the valve seat ID which you referred to as the “LD value”), you mention that for all the CDO cams you have data for, all but one provide LD flow potential of ~ 30%, does this include the stock CDO cam. I ask because just eyeballing the lift curve of a stock cam makes this observer think the LD flow potential would be far below 30%. In arriving at this conclusion I was thinking the valve seat ID might be ~ 1.40” and the LD lift point would therefore be 0.350” (1.40 * 0.25 = 0.350”) as I looked over the lift curve. Are these values reasonable datums for examining stock and other lift curves?

One final question on your following statement.

Losses on swings outweighs gains on the roundabout (or vice-versa!)


I realize the foregoing was directed to Eddie, thus a Commonwealth to Commonwealth communication. However, this dumb Yank is in need of a translation, so perhaps you might try it one more time for my edification. I know that swinging can result in large losses, e.g., a relationship, wife, children, etc, and roundabouts are a sort of new traffic control device over here that are being installed with some regularity this century, whereas I suspect you’ve been employing roundabouts since medieval times. Anyway, if you might be so generous as to restate the above passage I would appreciate it.

PS – all Yanks are not as stupid as me so don’t assume that my inability to understand the above quote exists throughout the general population.
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Re: Head flow testing.

Postby comnoz » Wed Mar 02, 2016 8:45 am

(also it's swings and roundabouts) UK saying› said to ​mean that the ​positive and ​negative ​results of a ​situation or ​action ​balance each other: "The ​route through ​town would be ​shorter, but there'll be more ​traffic." "Well, it's just ​swings and ​roundabouts."
(Definition of what you lose on the swings you gain on the roundabouts from the Cambridge Advanced Learner’s Dictionary & Thesaurus © Cambridge University Press)
"If the facts don't fit the theory, change the facts." Einstein
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Re: Head flow testing.

Postby WZ507 » Wed Mar 02, 2016 8:56 am

comnoz wrote:(also it's swings and roundabouts) UK saying› said to ​mean that the ​positive and ​negative ​results of a ​situation or ​action ​balance each other: "The ​route through ​town would be ​shorter, but there'll be more ​traffic." "Well, it's just ​swings and ​roundabouts."
(Definition of what you lose on the swings you gain on the roundabouts from the Cambridge Advanced Learner’s Dictionary & Thesaurus © Cambridge University Press)

See, I told you all Yanks were not as stupid as me! :D
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Re: Head flow testing.

Postby Snotzo » Wed Mar 02, 2016 9:06 am

Jim

sorry you had trouble with 'swings and roundabouts', I thought it was a universal saying, but obviously not. Perhaps I could have put it better as 'you gain some, you lose some, and as often as not you find that the gains balance out the losses'.

I didn't include the stock CDO cam because I have never had an opportunity to measure one, but if you have an S96 file for one that you can send over, I'll do the necessary and report back

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Re: Head flow testing.

Postby comnoz » Wed Mar 02, 2016 9:57 am

Snotzo wrote:Jim

sorry you had trouble with 'swings and roundabouts', I thought it was a universal saying, but obviously not. Perhaps I could have put it better as 'you gain some, you lose some, and as often as not you find that the gains balance out the losses'.

I didn't include the stock CDO cam because I have never had an opportunity to measure one, but if you have an S96 file for one that you can send over, I'll do the necessary and report back


Oh, I didn't have trouble with swings and roundabouts. I always equated it to "no free lunch"

I do have a file but it's in my PC with the dead motherboard. I will have to spend some time recovering them. Jim
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Re: Head flow testing.

Postby brxpb » Wed Mar 02, 2016 11:52 am

Perhaps our trans continental friends understand the term "6 of one half a dozen" of the other" ?? Used more widely in the UK prior to joining Europe and "metrification" :?
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Re: Head flow testing.

Postby Snotzo » Tue Mar 22, 2016 2:29 am

WZ507
As is so often the case, thank you for allowing us to see what we always see but think what some of us (me) have never thought. With respect to your comments about the fifth lift point (valve lift = 25% of the valve seat ID which you referred to as the “LD value”), you mention that for all the CDO cams you have data for, all but one provide LD flow potential of ~ 30%, does this include the stock CDO cam. I ask because just eyeballing the lift curve of a stock cam makes this observer think the LD flow potential would be far below 30%. In arriving at this conclusion I was thinking the valve seat ID might be ~ 1.40” and the LD lift point would therefore be 0.350” (1.40 * 0.25 = 0.350”) as I looked over the lift curve. Are these values reasonable datums for examining stock and other lift curves?


The valve seat inner diameter that I used for my calculations was 1.405". 25% of this diameter added to the tappet setting is the valve lift that determines the LD value.
I have now been able to examine the stock Commando cam, and find the LD value is 12.9% pretty low as you so rightly assumed.

What would an optimum LD value be for the standard intake valve ? It's really a case of swings and roundabouts (now Jim has told you the meaning).
Assuming high performance is the aim, an increase in valve diameter autamatically increases the area of the valve curtain at any given lift point, while adding extra valve lift for a stock valve increases the stress levels within the valve train. A bit of both might be the obvious way to proceed.

Out in the big wide world there are now 2 valve high performance engines with LD values at the 50% mark and more, while some high performance 4 valve engines are at 45% and more, but in this latter instance, the two intake valves magnify the end effect somewhat.
I haven't come across any Commando cams that give 0.5" lift at the valve as yet, but I'm sure someone somewhere had tried.

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Re: Head flow testing.

Postby Fast Eddie » Wed Mar 23, 2016 1:59 am

Just unpacked my head, having received it back from Jim.

Wow!

Looks better than new, inside and out. I don't know exactly what process Jim uses to clean up the casting (perhaps you can clarify Jim?) but it looks awesome.

Really keen to get it nailed back on and tested now.

I also have a brand new Maney lightweight crank sitting on the bench that also looks stunning. After great deliberation, I am going to RESIST fitting it this time in order to dyno test the head mods in isolation on the dyno. I hope you boys appreciate the sacrifice I am making here in the name of Norton Science...?!?

Y'all have to be patient though... I'm in Japan for a month...

Sayōnara !
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Re: Head flow testing.

Postby comnoz » Wed Mar 23, 2016 1:47 pm

Fast Eddie wrote:Just unpacked my head, having received it back from Jim.

Wow!

Looks better than new, inside and out. I don't know exactly what process Jim uses to clean up the casting (perhaps you can clarify Jim?) but it looks awesome.



I use a vibratory mill with ceramic beads to peen the surfaces. Jim
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Re: Head flow testing.

Postby Mr.Sparks » Fri Mar 25, 2016 5:27 am

+1 on that finish. Looks almost pearl. :D
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Re: Head flow testing.

Postby comnoz » Thu Jun 09, 2016 4:37 pm

Here is the next shortstroke project cylinder head. Too many hours in this one.
A Fullauto head with 44 mm intake valves and 36mm exhaust valves for an 83 mm bore.

Image

Here is the initial flow test. The bowl is finished and I am working on establishing the correct choke size in the port [the cross sectional area of the smallest part of the port]. This is with the original port size.

phpBB [video]


Here is the resulting graph. You can only move air so fast. The white line is a 41mm big valve head and the blue line is the 44mm job. Starts out good...

Image
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Re: Head flow testing.

Postby comnoz » Thu Jun 09, 2016 9:33 pm

Here is what I ended up with after removing a surprisingly small amount of material. No more earsplitting roar.

Image

Image
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Re: Head flow testing.

Postby Kvinnhering » Fri Jun 10, 2016 12:05 am

Wow Jim! For an velocity!
You must soon reach the limit of what is possible with a Fullauto head! You taught me what a high air velocity means in practice. My short stroke with head from you preform very well! Can not wait to see the power figures on your new short stroke project.
Good luck Jim!
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Re: Head flow testing.

Postby comnoz » Wed Oct 26, 2016 8:27 pm

"If the facts don't fit the theory, change the facts." Einstein
You're never too old, to learn something stupid.
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Re: Head flow testing.

Postby lcrken » Thu Oct 27, 2016 10:36 am

+1. Good article. I've been saving the tech articles from the engine builder site for a while now, and they have published some really good stuff. I particularly liked their articles on piston technology. If you're interested in the tech stuff, it's worth browsing their site for other interesting articles.

Ken
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