LAVERDA Triple 4-valve head

Lothar, rule of the thumbs says that the reason for a 4-valve head is the higher charge and resulting higher
peak power. If you optimize an engine for a higher charge, this is usually at the expense of the lower and
middle speed range (if you leave variable control times, etc. times out).

Of course, the purpose to go for an 4-valve head is also important. If I for example think of the further planned
optimization of my 3c, a 4-valve valve head would be out of the question. Redax may see it differently, he is always
on the lookout for performance (but he has to pay attention to the regulations).

I find it admirable to even dare to do such a thing. However, what strikes me in the present 4-valve design, is
the amazingly small difference in the diameter of the intake and exhaust valves. Control of heat in the exhaust
valve area could also be an issue ...

jm2c
Jo
 
Bloody hell!
These things already have at least one cylinder too many, and one cam too many, and now its valves are multiplying.

Paul
 
looks a lot better in the flesh than on the drawing(where the valves look puny) and as PM says, too much, more power equals more BMEP which equals more heat and no where for it to go.
CLEM
 
Does four valves always equate to more power? Or more importantly, more USABLE power? Modern engines have massively oversquare bore-to-stroke ratios, giving a much larger potential valve area than a 'traditionally' jigged (say 81x74mm!!) motor.

And it follows that these modern engines with short strokes rev probably 50% higher than our old clunkers of eq capacity, and IMHO it's at these elevated rev ranges that four valves are probably obligatory. I'm no mechanical engineer, so I could be totally wrong.

If Red could get more USABLE power out of his race motors by using a four valve head without going into rev ranges that will see the bike rarely finish a race, then he would probably do it.
 
The 4 valve DOHC cylinder head concept boils down to lighter valves hence higher revs and less wear due to less reciprocating mass - Not necessarily increasing air flow compared to using a big single diameter heavy cast valve.

Italians where 1st to use this DOHC 4 valve Hemi engineering concept back in the 1920's but unfortunately did not have the Alloys to make the engine sustainable.

Today: You can get around this by using a big diameter shaved stem Ultra light single stainless steel valve or expensive titanium and confidently hit 8000 rpm without valve failure in our "OLD"  4"x2" bore/stroke SOHC and DOHC Air Cooled Hemi-Breganzies.

I've have feeling Chrisk will bounce in on this ;o)
 
Piranha Brother 2 said:
Does four valves always equate to more power?
Click to expand...

According to Phil Irving, the power produced by any engine comes from the cylinder head. The pistons, crankshaft, and all the other bits just convert the reciprocating motion to rotary.

It's the cylinder head and associated gear (valve timing, etc.) that makes the difference. The more gas you can flow, the more horsepower you'll get. So I suppose the short answer is yes, four valves are better than two.

However, the problem with increasing power is that the rest of the engine structure has to be strong enough to handle it. That's one of the areas where Red has been doing some good work. I suspect he's getting more power out of the old Laverda triple engine than anyone else ever has, and he has run into problems like crankcase flexing. Beefing up the crankcase and main bearings, as well as the gearbox with his sleeve gear outrigger has made his engines more reliable - as demonstrated by the recent flawless performance at Darwin BEARS. If he ramps it up to the next level by flowing more gas through the head, then other weaknesses in the engine design may reveal themselves. For example, I dunno how much more power the duplex 'Merc' primary chain will handle. I don't reckon that'll stop him trying though. I find his engineering work very interesting.

Incidentally, I used to work on diesel truck engines that had 4-valve heads, but they were all exhaust valves.
 
How many air-cooled Big bore Japanese bikes had 4 valve heads, when did they all go water-cooled. How much power and where was it in the rev range in those air-cooled Japanese bikes. There was lots of Drag bikes using Kawaski and Suzuki engines but not for long time periods, those engines are where all the competition to Reds bikes come from. Some had oil jets directed to under the pistons to reduce temperatures. I once had a look inside a set of Bevel Ducati cases used in high-end racing years ago and I was amazed at the welding they used to stop them flexing. Lots of work and mods to be competitive as time moves on.
 
Dellorto - Sorry I forgot you - Suppose the diesel 4 stroke exhaust valves where cast iron sodium filled - Not necessarily to lighten but to dissipate the heat under Hi-Compression.

To say 2 heavy Big DOHC Valve Engines can't flow the same amount of Air Flow Vs a 4 Valve Head is irrelevant; however, 4 valve DOHC Heads tend to rev higher and reduce mechanical wear in a Hemi Head providing the metal ergy is compliant. Look at the early years Honda, Kawasaki and Yamaha struggled with this and yet our OLD 2 Valve Hemi Berganzies survived.

Granted we where not hitting 10,000 rpm for short intervals before a Jap engine melted.

Today's story is a different matter !

Look at the modern BMW FZ850 for instance. It's a 850cc DOHC 4 Valve 10,000 rpm Hemi Water cooled Sport Twin - Single side chain drive and the KTM DUKE - We don't stand a chance in HELL !

The only thing we love to work on our Breanzies on our Wife's kitchen table.

 
The Diesels I worked on with 4 exhaust valves were 2-stroke GM engines in Terex trucks. They had inlet ports around the sides of the cylinder that would open when the piston was at the bottom of its stroke. The fresh charge was blown in by a pair of great big Roots blowers sitting on top of the engine, while the 4 valves in the heat would exhaust the spent gases. I don't know whether the valves were sodium filled, but I doubt it. The engines weren't that fancy. They were just big old dump trucks that worked in an open-cut iron ore mine. Nothing too high-tech about them.

One thing I do remember is that we were forever replacing busted leaf springs under the damn trucks. Bloody heavy great springs that we had to man-handle around the floor and jack up into position. Another regular failure was front stub axles. When they snapped off, the front wheel would go with it. It would sometimes happen near the top of the open cut mine, and the errant wheel would roll/bounce all the way to the bottom of the pit. Bloody big wheels and tyres on those things. You wouldn't want to be standing in the way of one when it's bouncing down the road. Must have been a bit scary fore the drivers too when a wheel fell off and the truck would suddenly lurch toward the edge of the pit with 50 tonnes of ore in the back. It was a long way down to the bottom.

They were fun trucks to drive around the workshop yard though. Not much attention was paid to health and safety back in those days. :D
 
4-valve bike engines literally annihilated the 2-valvers the moment they appeared on the market. 

At a given displacement, a 4-valve engine will produce more torque, hence also more power, as power is the product of torque and rpm.  What killed the big Jap air-cooled 4-valvers so quick were the stringent noise emission reulations imposed at the time, so in came liquid cooling to quieten things down.  Handy side-effect was the temps stayed consistantly low, so even more power was able to be extracted, even if the engines all turned ugly.  But, by then, they were mostly hidden behind fairings.

If torque is to be produced low or high in the rev range can be easily controlled by the cam profile and timing, together with comp ratio.  Twin sparks would only really be required for individual cylinder displacements >500cc.

I admire Gijs for the effort he has put into this project, reckon I'll get one as soon as possible. :D

piet

 
Jo said:
Lothar, rule of the thumbs says that the reason for a 4-valve head is the higher charge and resulting higher
peak power. If you optimize an engine for a higher charge, this is usually at the expense of the lower and
middle speed range (if you leave variable control times, etc. times out).

....

jm2c
Jo
Click to expand...

Hi Jo, I think to remember you have an engineering background, which I respect, please. I suppose the original design is - compared to todays knowledge and possibilities - so inefficiant, that re-designing it completely will improve torque and power in all rev-ranges.

I have made my experiances which we can discuss offline if you like. I broke many of these "rules of thumb" to the surprise of a lot of people, me included.
 
Since Gijs himself is not starting this threat, it shows how Rational Humble and Realistic he Works. The 4V Head is for Racing only, he works with a motoGP Man to make shure not going too much wrong here. Anyway, his Racing Sucsess and Experience should keep us little Quiet in smart Talking...
 
I can't see anything wrong with sharing thoughts and oppinions on these modifications. Gijs has made it public already (Facebook, having the parts on display etc.), so I guess it would not really surprise him if people talk about it...

It's a free world and everyone can have a different view. Many things of what I did or asked professionals to do made experianced people shake and/or scratch their heads. I did it for me and my personal fun and learning and it was a good experiance.

Gijs indead has a great experiance in racing and if he has a GP-experianced person to help him, I trust it will come out extremely powerfull at the end. Let's not forget, time moved on 50+ years since this engine was designed. I would be shocked to the bones if someone could proof me there would be nothing to improve anymore on these engines... :D
 
So what's the point of being here if you don't express an opinion. Anyone producing anything as important as a head deserves full respect and an excited chatfest from the peanut gallery. If only championship-winning builders can comment it will be a short conversation.
 
When you say that he is developing this head primarily for racing, the question arises for me how that is in terms
of regulatory compliance. For example, I know Gijs' missions in the 'Europen Classic Series' - as far as I know, the
engine there in the key data must correspond to the historical series counterpart. Which race series allow such a
modified engine according to regulations?

I admire Gijs work absolutely! The thoughts I expressed were not intended to criticize or question his work.

Cheers
Jo
 
Jo said:
When you say that he is developing this head primarily for racing, the question arises for me how that is in terms
of regulatory compliance. For example, I know Gijs' missions in the 'Europen Classic Series' - as far as I know, the
engine there in the key data must correspond to the historical series counterpart. Which race series allow such a
modified engine according to regulations?

I admire Gijs work absolutely! The thoughts I expressed were not intended to criticize or question his work.

Cheers
Jo
Click to expand...

I don?t know this, must be the Same for Guzzi 4V, TR1, Britten...
 
If the Euro classic endurance series is like it used to be back in the day, it used to have classes for anything goes (within reason I guess), hence things like Nessie and Eric Offenstadt?s creations. Pretty sure motors could be innovated too. Would be interested to see the results of his work in action.
 
Maybe it's a silhouette class, where externally thing have to look standard but inside anything goes, like the modern NIkasil barrels on Guzzis with the square fins turned down to round to mimic the early Guzzi barrel appearance.
 
Just the barrels LOL. Whole bloody ?96 1100 Sport engine in the up to ?79 class here and they don't even bother rounding the fins off any more. Would be a very depleted field without them though. My 750 SF2 beats some of them regardless.
The two valve Suzuki GS motors are the choice here even when the 4 valver can be used, more power etc, say the punters.
 
Not sure where Gijs and his team participate, but if you look at the 4 hours of SPA during the Bikers Classics, Dynotec takes regularely part with their "Guzzilla" which I think is also a 4-valve head conversion... Not talking about all the Japs bikes that are massively modified... Pretty sure they simply don't care as long as all the bolts are secured and the catch tank is installed...
 
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