Big valves or small valves

jseng1 said:

Yes the FA head is a very good place to start.

Back to big valves. Here's a few winning bikes with big valves.

Ron Woods winning flat tracker with AMA factory big valve head (3mm oversize intakes I think). Alex Jorgensen and others riding.

Dave Watson's 1000cc roadracer with 5mm oversize intake and 3mm oversize exhaust valves (Maney stage 3). Gary Twaites riding.

Ken Canaga's monoshock 920 that took 3rd at Willow Springs against a field of air cooled monoshock Ducatis. The last Norton to get on the AMA podium approx 1990 with Rob Tuluie riding. Pretty sure it had big valves - Ken can tell us.

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I think it is likely that the head on Ron Wood's bike was using even larger valves. I have one of his heads that Axtell flowed and fitted with larger valves. I got it from Ron without valves, but from measuring the valve seat diameters, it looks like he was using valves very close in size to the ones used on the factory race head I have, which are 1.696" intake and 1.370" exhausts (~43/35 mm).

Ken

For those interested in this subject, I'm posting this table of data that I've collected over the years. I've posted it here before, but this is the latest update.







Ken

If larger valves give better performance, the best time to modify the cylinder head shape s when you are making patterns to make after-market ones. If you modify a standard head, you are usually buying a pig in a poke. What you get might be better - OR NOT. Theorising is often at variance with what happens in practice. Sensibly an increase in area when the valve is open should give an increase in power. But if the areas is smaller, the gas flow probably speeds up, so the gain with a larger valve would be minimal. The trade-off might be valve bounce. So the revs at which the motor is mostly used and the cam are important.

The first time I met Rob Tuluie we raced in different classes at Laguna Seca. It was his very 1st race ever. He didn't even have a decent street bike (I think he rode a Vespa scooter) but somehow he assembled a Norton road racer and made his entry fees. So what does he do? He goes out and wins a National race (BOTT 750 I think). Thats impossible - but that's what he did. When they stuck a microphone in his face at the Winners circle he was so overcome with emotion that he couldn't get his words out.

He probably did not know any better, so he rode faster.

Or he may have been desperate.

worntorn said:

Or he may have been desperate.

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Can you imagine Rob in twenty years time coming on this forum lol
And his first post will be;
When I used to race my Commando I used to ride under everyone going into the corners.
They couldn't catch me.

To finish first first you must finish.

In my defence I was better looking than Ago but not as desperate.

Rob is quite the interesting guy. I got to know him quite well back when we were both racing Commandos. Besides being a very talented racer with many race wins behind him, he also managed to acquire a Ph. D. in astrophysics, build a couple of innovative race bikes (google the Tul-da and the Tularis), and work at a variety in interesting jobs in the motorcycle and auto racing industries, including chassis development at Polaris for the Victory motorcycle, developing the first 2-post hydraulic chassis simulator/shaker at MTS, then head of R&D for the Renault F1 team, later moving to chief scientist and head of R&D for the Mercedes F1 team, and then to director of vehicle technology at Bentley, as well as consulting for the Ducati Motogp team. I last saw Rob a couple of years ago on a visit back to the States (he's been living in England since moving there to work for the Renault team), and he's still going strong as chief scientist at Keselowski Advanced Manufacturing (KAM), consulting to a variety of companies, as well as building and driving a vintage racing car. For anyone interested, there is some more info on him in these links:





These are a couple of pictures of Rob with his Commando race bike at a motorcycle meet somewhere in Texas. He had ridden the bike there and back, with no license plate or lights. He was a pretty wild guy.





And this is a bit more recent picture of him, when he was with the Renault F1 Team. A little older, a little grayer.



And a more "casual" picture of him in his vintage race car.



Didn't mean to hijack this thread, but Rob is one of the more interesting people I've known, and I couldn't resist passing on some of his exploits.

Last picture, I promise. This is me on Rob's Polaris powered bike, the Tularis, at Willow Springs coming down the hill from the Omega. I think that was in 2006. I haven't been on track with a bike since.



Ken

Interesting indeed, quite an accomplished lad..
Thanks for sharing.......

Ken - I don't mind talking about Rob. When Rob was starting out he used to call me up and talk for hours. He had so many questions - an insatiable lust for racing technology (I was the same when I started out and I used to drive Mick Ofield out of his mind - Mick worked in the Norton factory race dept).

Poor Rob would stay up all night working on his bike - making his girlfriend stay up and help him as if that what love was all about. We were young and full of energy back then.

Which brings me to a memory of you Ken. We were on our way to a race in Nevada I think, got hungry and pulled in to a hamburger joint. They were absolutely the worst hamburgers ever made - dry as cardboard and impossible to force down or keep from choking without gulps of soda. I for one would have left the food but I was starving to death. Then some poor fool started ordering and he asked several times if the hamburgers were really good (he must have heard otherwise). They reasurred him and then he said "OK, I'll take two of them." - And thats when you and I busted out in hysterics. It was a golden moment for sure.

So if some guy is faster than you on another Norton, he must be using bigger valves ? - Might be the ones in his heart.

acotrel said:

So if some guy is faster than you on another Norton, he must be using bigger valves ? - Might be the ones in his heart.

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Only if they are desparate heart valves!

In 1969 I had 650 Racing valves and springs installed in my Triumph 500 head. I installed hot cams and 13:1 pistons after having them machined to miss the valves. Then I had to file the rockers to miss the collars and buy special pushrods. When all done. I had the fastest 500 around but had to gas up at the airport. I was all proud until I raced a stock Triumph 650. Shortly after that, the bike was stolen. Those "improvements" cost me around three times what the bike cost. Stupid 19 year old.

If want power - add nitrous, a super charger, or a turbo charger If you want a more or less stock modified bike and REALY want power, get one of these:

Here's a comparison of stock valves to big valves.

Top row - stock exhaust and 3mm oversize exhaust.

Bottom row - stock intake, 3mm oversize intake, 5mm oversize intake

I got lately due to job related edu classes a hint of track regarding this topic.
I still do not seem to understand why some people do not like to understand or obstruct the idea/logic of using "suitably sized" larger valves.
The max gas velocity (0,5-06mach) needed for maximum volumetric efficiency does not necessarily need to be at the valve seat or valve choke area.
It's of course critical what size valve gets put in use, because in enlarging the intake valve/intake valve throat area one also enlarges the overlap area, which depending on use is depending on used camshaft (eg overlap in relation to lift) is not always wanted. This is a detail that can be overcome by using camshafts with steeper ramps and starting with less overlap area.
Point is Imho (as well as regarding my experience), it's almost always better to rip the barn door "quickly and fully" open when there is the highest "quasi static" (piston velocity)demand in order to lower throttling losses and turbulences on the port SSR.
Although equally important is to not neglect the focus to keep the needed gas velocity up to par with the max Tq/hp targets dictated by eg intake valve closing point for highest volumetric efficiency.
Furthermore, admittedly and old story, ports should be "always" imho religiously ported with an emphasis on a high coefficient of discharge meaning the more flow through an area the better (within needed intake mach) the better it is.
Sorry if my rambling is cut a little short but trying the content of almost full text books on the topic within some short sentences is not the easiest.
All the best and happy weekend

Christian

I'm interested in any info on increasing midrange power.
I haven't found any published material on modifications to improve 3500-5000 rpm power in the Norton twin.
There is lots of info on efforts to improve the high rpm output with generally no mention of midrange. The Dunstall stuff is all aimed at using very high rpm ( for a Norton with stock cases and crank)
Ken Canaga and Jim Comstock have given me virtually the same advice, which I've followed with the 920 build. It's probably all the advice needed, however I find it strange that there is so little discussion of building a midrange engine and so much on high rpm racing, which isn't really the Norton twin's forte.
Here on the west coast of Canada we sit at about 100' above sea level and have to climb again and again on every big trip. Some of the passes are as high as 10 to 11 thousand feet.
It's not just one mountain range but a series of mountain ranges that are encountered.
I looked it up, there are over 8000 named mountain peaks in BC, another 3500 in Washington and so on. In all, with the areas I ride in, BC, Alberta, Washington, Montana, Wyoming, Oregon and California there are about 35,000 named mountain peaks. Most days you are constantly climbing or descending, there is very little riding done in flat country.
You really don't want to have to grind away in third gear all day, midrange torque that will give good uphill passing power in top Gear is essential.
I will say that the standard 850 seems naturally suited to this type of riding, even though I doubt the designers were thinking of western N.A. mountain ranges. The 750 is not so well suited to this riding, and I suspect my 650ss would have to pedal a little harder than the 750. I've never tried using the 650ss as there are better choices here for those kinds of trips.

Glen

If you want an increase in mid range then you want the FA style head with the smaller raised ports and higher velocity. But don't expect an improvement in top end. I know of one builder who did some testing and says the top end is decreased with the smaller FA ports.

jseng1 said:

If you want an increase in mid range then you want the FA style head with the smaller raised ports and higher velocity. But don't expect an improvement in top end. I know of one builder who did some testing and says the top end is decreased with the smaller FA ports.

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How can the FA cylinder head have smaller raised ports when stock 32 mm/32 mm RH4 inlet manifolds bolt to it with no real mismatch, I was surprised to find the port entrance was bigger than those on the RH10 I removed unless you mean the tiny D exhausts and those ports out of the box are very average as cast. (and left as is)

I have to wonder what that head is like in real world riding back to back with a stock RH10 given the same size valves, the FA would want to add mid range power out of the box or it would be somewhat pointless to a good deal of riders.
#
I can say with my very modified (including big valves and welded chambers) 1981 Ducati, with the stock heavy outer sprag clutch flywheel it would happily pull down to 50 km/h / 30 mph in fifth gear which it would not like with a severely lightened one (plus the 2.2 kgs / 5 lbs removed from the crankshaft counter weight)
Any engines character can be changed or moved with altered rotating weight or loss of stored energy as above.

Big valves (State of tune) light or heavy flywheel can make a lot of difference. (I found)

To be clear, I'm not looking for a motor that will pull way down in rpm and happily grind away. " Lowest snatch speed" was the famous phrase in the old UK magazines.
The desired thing is a motor that is already somewhat revved up (4,000 rpm) and has enough grunt to accelerate hard against a big hill and headwinds without needing to shift down run near max rpm for long periods of time.
Anyone who rides in the mountains a lot will appreciate this type of tune.

Glen

Time Warp - the FA head may match at the manifolds (for marketability) but it narrows top to bottom to about 25mm height deeper in the intake port. Unfortunately the FA port floor level doesn't match the manifold floor level - its way off. Compare floor of stock port floor (green line) to angle of FA floor. See image.

worntorn - a 1007cc Norton should give you what you want. All it takes is $