should i fit a big valve head?????

I just appreciate the approach Don took in doing the brake upgrade in order to make it right. I dont think anyone else has made up a custom fork bottom with correct mounting points for their big caliper cast into the piece. So to me that is a preferable look over a bracket. Same with the mastercylinder, he went to great pains to ensure it fits right onto standard Norton switchgear, which is nice looking stuff.,preferable to fitting generic plastic or other items on there. Plus it makes the kit an easy install.

Glen

comnoz said:

I know, that of all the modifications I have done to a Norton motor except raising the compression ratio, increasing the intake valve size was the one that required the least amount of tuning and messing around to get it to work.

It does require checking and modifying piston valve reliefs and usually requires jetting changes. It works well with the stock cam and exhaust system. It does not change the original rpm range of the engine. Jim

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+1

@toppy, the above from comnoz is the concise summary you need.

Say hello to Dave for me when you see him.

Yes I picked up on that. I will see what Mick Hemmings recommends on Monday as it is he seem a nice enough man to deal with (no offence ment to others on here who sell nice stuff to) an he is only couple hour drive away. Some of the stuff available across the water looks great but its along way form here an shipping an import charges can drive the price right up I have found before.
Should I tell Dave that Dances said hi or does he call you Mr Shrapnel???

@toppy

PM sent

toppy said:

Yes I picked up on that. I will see what Mick Hemmings recommends on Monday as it is he seem a nice enough man to deal with (no offence ment to others on here who sell nice stuff to) an he is only couple hour drive away. Some of the stuff available across the water looks great but its along way form here an shipping an import charges can drive the price right up I have found before.

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Not a problem, I wasn't trying to sell more work. Jim

worntorn said:

I thought Jim's summary was pretty simple to understand, but let me attempt to rewrite it in Hobot langauge:

"Big valve power spreads to gravel flying and kids crying with no change to port, full snort in every galaxy. Hold on till it really hits a 4 k then rear wheel spin rolls up asphalt until the end of the road smacks you down, on and on you go past ballon tired corner cripples and triple A fuel dragsters until the speed of light becomes a hindrance to pull you down, swallows both you and your bike only to catapult both into a much faster but parallel universe."

After reading this thru again I think I have to have one, a want has become a need. :mrgreen:

Glen

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Gidday Steve

whats going on mate. you have not dropped the ball have you.

I really like the unique way you express yourself and yet here we have a Glenbot speaking fluent hobotese. cant have that. I am sure you can respond with the mother of all hobotese stories. just like looking for Waldo post. that is classic hobotese.


Glenbot, i admire your perserverance in becoming fluent in a very difficult language.

all this friendly banter is what makes this forum special. keep it up . apologies for the hijack but it is brief.
best wishes to all Bradley

[video]http://www.youtube.com/watch?v=9I1ksEz6oSI[/video]

To get back to the initial question, having followed Comnoz's posts on head flow work recently, if you've got yer motor down that far... And yer wallet open that wide already... then YES, do it!
Nobody ever said this was a cheap game, and if you don't do it, you'll always be wondering how much better it could have been if you had...!

There are no roof racks on the Hearse, have fun now!

I would have thought a decent two into one exhaust and playing with the cam timing and gearing would give more benefit.

acotrel said:

I would have thought a decent two into one exhaust and playing with the cam timing and gearing would give more benefit.

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There is no question. Having everything working together [in tune] is the single most important power adder. I would include intake and exhaust systems, cam timing, compression ratio and ignition timing.

But adding a larger intake valve does little to change the balance of the tuning variables. It simply adds torque. Jim

And Tourque x rpm's = Horse Power .

Circumferance of valve is bigger , therefore the ' window ' is greater by the differance in circumferance as a percentage . approximately .

A decent 2 - 1 exhaust can probaly bolt to the cradle , so it wont fall off , but Im not sure that it isnt more of a race option , likely the biggest advantage being easier compliance with noise regs / decible meter .
Id prefer the beat of the dual exhaust.

If a 2 into 1 , Id use slip joints to tune the lengths . And still do a comparison with stock headers with unobstructed mufflers to check if it did help .

Sticking to the subject - would bigger valve help or hurt a 2>1 or not, not that a good extractor corss-over mergered exhaust can have advantage over other systems, no matter the valve size. If valve is the main restriction then either stream line better, make bigger or both. Likely someday I will find out on Peel's deal starting off with stock sizes. Would be neat to see a before and after bench test and dyno.

How much does stem size matter?
How about them hollar or sodium filled valves?
Beryllium anyone?

At this stage of the proceedings , we will have to consider it gross cowardice , if a big valve head is not fitted . In this particular case .

And Tourque x rpm's = Horse Power

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Don't forget to divide by 5252.

comnoz said:

acotrel said:

I would have thought a decent two into one exhaust and playing with the cam timing and gearing would give more benefit.

Click to expand...

There is no question. Having everything working together [in tune] is the single most important power adder. I would include intake and exhaust systems, cam timing, compression ratio and ignition timing.

But adding a larger intake valve does little to change the balance of the tuning variables. It simply adds torque. Jim

Click to expand...

Whether intended or not, someone is going to get some business. It's got me thinking.
More torque? Duh! 100mph to 110mph is all I ever intend to venture to. How quick I can get there is whole other aspect. To me this is what it is all about. Midrange mayhem, baby. Yeah!

Those forks on the bottom of that crank are never going to work as a bob weight.

[/quote]

Fitting a bigger inlet valve might improve torque ? I've never tried just altering the valve size alone, usually it goes with a port job which changes the torque characteristic in the opposite direction ? The two into one pipe I use, could not be used on a street bike unless you have very liberal laws applying to road bikes. It has a very loud bellow due to the skinny header pipes, large tail pipe and absorption muffler, however it works extremely well. Also my cam is advanced to compensate for the back pressure, and because the exhaust valve is open earlier the noise is also louder on account of that. I can only suggest you try this, it seems to work very well as long as you up the gearing. If you don't do that the acceleration rate doesn't seem to increase. I find it very strange when I drop a tooth on the back sprocket and the bike accelerates even faster. I think commando engines are pretty weird with that long stroke and heavy flywheel.
I'd be interested in trying a bigger inlet valve, however once it is done it is difficult to reverse if you don't like the result.

Today I have been to Mick Hemmings an left the crank an rods for regrind and full balance with new old stock genuine EA pistons he is supplying to match the rebore he will have done. Also he will be supplying genuine baskets bolt head nut bearing etc. and assembling the crank an rods. He looked at the head an rockers an said the pushrods will need shortening as the head has been skimmed in the past. I noticed for the first time the tab washers of crank had not been bent over he said he had seen may come out of the factory like that!! I explained it was a road engine an had twin carbs an big bore exhaust with longer than standard pipes an I have PW3 cam an asked his advice add I wanted all new valves new springs bronze guides and titanium collars regardless of whatever other mods where done he said that bigger valves and porting of inlet an exhaust would be the way to go as valves and guides where to be replaced anyway. He will port the head accordingly an he assured me I will be impressed that was what I wanted to know an he does after all have a little experience at it!! The bill is shaping up to be quite impressive to. But stood in his shop looking at his famous race bikes (an touching them to) in this little old fashioned timewarp place you feel he has been here so long an done so much he know what to do.

Dance with Shrapnel I when to see Dave Nourish today as well and as you asked I said hello for you. He was pleased you like his engine an remembers you. He says feel free to call him anytime. As I stood in his over crowded workshop looking at the old machinery I was explaining to my friend I when with what some of them where an how to work them Dave asked how I new I said I have used them before he said don't just stand there get some overalls on an get working !! Does that count as a job offer I wonders??

I'm surprised that he would open up the exhaust port and use a bigger exhaust valve on a road bike. The current thinking on many engines seems to be more along the lines of a bit smaller exhaust port overall, with the reduction coming in the form of a raised floor to prevent reversion. The raised floor is a bit hard to accomplish with an existing head I imagine.

Glen