Hi again,this post is directed mainly to ian wright ,but i,m sure there are others who could help. I am looking at another project which will require highly modifying a m20 engine. I have worked out a lot of capacities using o/s pistons and or m21 crank,but unsure of what comp ratio limits maybe, plus also details on cam spec and timing imformation will be required, are there any books or other, that could help me fill in the blanks. cheers Adrian jackway.

email (option): cruiser3@icisp.net

Hi Adrian..The first question I would have is what type of machine are you looking to build and how much do you intend to alter the engine...for example, do you want it to look pretty much standard externally? Is it a road machine or competition bike etc. etc.
These things will govern to a degree where you go with tuning it and what you can achieve....Ian

email (option): julie@wright52.plus.com

Hi Adrian..There is very limited information out there on tuning sidevalves...Harley Davidson 'K' model tuning information is applicable to a degree, though much is not directly transferable to the M20.
Any articles by Hartley, the famous pre war tuner (who specialised in Ariel tuning but also tuned others) is worth a read if you can find it. However, his articles are out of date to a certain extent.
There is also quite a bit of info. on tuning Austin and Ford sidevalves...this can help with basic principles as well.
There was also quite a good series of articles in one of the 'glossies' a few years back covering the subject in some detail...though I can't remember which one!
As in all things you will find conflicting opinions as to what is the right thing to do and what suits one engine type may not necessarily suit another.
Tuning sidevalves is inherently more difficult than tuning OHV engines by virtue of the peculiarities of their porting,general layout, and breathing and combustion characteristics. Additionally, there is no ready made template to follow if the M20 is the subject engine....Ian

email (option): julie@wright52.plus.com

It would be simpler to fit a nitrous oxide kit for those moments when you really need a little extra oomph. Beyond that, it's time to get all the extra weight off, drop the bars and fit a cockpit fairing.

On a more serious note, I think Phil Irving's book TUNING FOR SPEED has something to say about sidevalves, and that book turns up in autojumbles from time to time.

I have no idea how practical it would be. I have trouble tuning a TV.

email (option): dannydefazio@sumpmagazine.com

Hi Danny, Some kind of personality disorder is probably behind the urge to tune a sidevalve...its rather like trying to breed the worlds first flying elephant or turning base metals into gold. The words 'speed' and 'sidevalve' don't go naturally together.
It's a case of define a difficult task...spend months or years trying to resolve all the problems..blow in a lot of cash on experimentation,special parts and machining work and end up producing a bike that is slower than an average Japanese 250....I'm still trying to work out what went wrong ...Ian

email (option): julie@wright52.plus.com

Hi Ian, you can console yourself that it's not so much what you've got, as what you do with it. I think sidevalve tuners should persevere. Every once in a while, a lateral technical development comes along that suddenly changes the game. Maybe it's time to think forced induction of some kind.

P.S. I never thought of reversing the headlight (as in the picture that's just gone up). That could make all the difference.

email (option): dannydefazio@sumpmagazine.com

No forced induction if you are after the semi official British Record Danny...anything that reduces the reliance on power produced by the application of actual tuning skills is not permitted...bad form and all that...Ian

email (option): julie@wright52.plus.com

I've spent (quite) a few hours trawling the internet on this subject, but as usual no practical experience.
The Harleys did do some interesting stuff, as Ian says not necessarily applicable to our trusty steeds.
Firstly their valves seem to be located much closer to the cylinder bore so less distance for the gases to navigate, and less dead space for burnt or unburnt gases to hide.
They also neatly profiled both the top of the barrel and the underside of the head around the inlet valve, again helping gas flow.
The spark plug was located centrally in the combustion chamber - triangulated between the valves and the piston.
I can't remember whether they were into squish (expect they would have been) but there is info on the internet suggesting how to take advantage of this in sidevalves (i've saved a few files but not on this computer) - from just a squish band around the piston perimeter to having the non valve side of the head over the piston with just tolerance clear of the piston at tdc, with a small vee to allow (aid) the gas to escape. Presumably you would want a flat top piston for this?
Around 6.5 to 1 to 7 to 1 seems to be the upper end of comp ratio recommendations.
It seems you would be into making a custom head to get really serious.

The key problem with tuning a sidevalve is the conflict between compression ratio and gas flow...improve one and it will always be at the expense of the other.
High values for both are regarded as necessary and are easily achieved in the OHV tuning world, but you can't have that.
Complicating the issue further are the poor combustion characteristics inherent in the design of the sidevalve layout and the complicated gas path on the inlet side.
Add to that the problems created by uneven heat distribution and poor thermal efficiency and the difficulties start to become apparent!!
...Ian

email (option): julie@wright52.plus.com

Hi ian, back again,answer to first question is i,m looking at building a period 2 m20 (vintage track bike)so the bike will have to be stock looking to a degree,but might have to go on diet,but what hides inside is not a big problem,I dont have a lot of sidevalve principle knowledge , and yes they do have very poor combustion designs,but there strong simple and reliable and its not the first time i,ve tried making strawberry jam from pig shit ,its what keeps us ticking. but at this stage i,m just collecting parts and imformation,and like many others on a budget.Thanks to all others for the replies as well,and maybe i do have an m20 disorder but hey thats not a bad thing.

email (option): cruiser3@icisp.net

Hi Adrian..I've certainly got the disorder as well..
This is an extremely involved subject and it would be impossible to cover it all in a posting on the forum. I would recommend you get hold of the Harley K model tuning information...you will have to trawl the internet for this. A detailed study of that will give you a feel for the generalities and some detailed information regarding cam profiles, compression ratios etc. etc. As a brief (and broad)outline...go with the M20 crank...most of those are steel whereas most of the M21 cranks are cast iron. Also the stroke of the M21 is far too long to allow the engine to rev without exceeding sensible piston speeds. Lighten the crank quite substantially to allow it to rev. Camwise fit the largest inlet you can find...off the shelf that would be a DBD34 Clubmans cam. Match that with something like a scrambles exhaust cam.
Fit the largest inlet valve you can get in..the exhaust can stay as standard. Don't exceed a 7:1 compression ratio. This can be achieved by skimming the head if capacity is to remain at 500cc or if you choose to go bigger.
You will need to improve the gas flow in the inlet port as far as possible...and remember that the area between the inlet valve and the cylinder must also be regarded as part of the inlet port. The inlet port should also be substantially lengthened...a figure of 10" from the centre of the inlet valve to the outer end of the carb would be a good starting point....Ian

email (option): julie@wright52.plus.com

Thanks ian ,this is a great start point,and i will definetly search for the kr harley imfo as well,another question, you must have done a bit of tuning by the sound of that ,what sort of results did you acheive.

email (option): cruiser3@icisp.net

Hi Adrian, A lot of the engines I build for customers are tuned ones....mainly the OHV B Series with a Gold Star every now and again. With the B33 based engines I have (so far) managed to match the power output of a DBD 34 Gold Star ( 37.5 bhp at the backwheel measured on a Dyno). A bike to which that version has been fitted and which is used as a sprint/road bike has run a 13.3 standing quarter and has a top speed on the road of approx. 110-115 mph on its present sprint gearing.
I am currently working on an iron engine which I expect to exceed those figures when completed.
The sidevalve work has mainly involved improvements to my own M Series road bikes. However, I had been contemplating building the sprinter project for some time and I took the opportunity to find out by experimentation where some of the problems and limits lie in tuning these types whilst making changes for the road.
The final versions of these road bikes are not particularly fast and that was never the intention. I particularly wanted my WD bikes to remain unaltered externally and this led to a self imposed limit on the end result. Nevertheless I am very happy with the degree of improvement as compared to a standard machine.
With this knowledge in hand and with the information I gleaned from every bit of sidevalve tuning info. I could find over about 3 years I then started afresh and laid down the overall specs. for the engine I am currently working on. This is the one which I hope will be the fast one! Success is not guaranteed however. As I said in my previous posting there is no convenient template to follow and what I am putting together is an amalgam of the results of my own experiments, other peoples previous work, a degree of 'received wisdom' regarding the subject and crucially (I hope)in the case of the M20, some new ideas of my own.
Time will tell whether it is a success or not...Ian

email (option): julie@wright52.plus.com

in the late seventies i was slightly involved in hot rod/stock car oval racing the engine tuner i knew he found that to smooth/open out inlet/exhaust ports to get more bhp you could over smooth/open out the port and get less bhp he lost a few head in this way

Hi Roger...to smooth or not to smooth is one of the never ending debates in the tuning world..Some believe that if you polish the ports you will get better gas flow, whilst others believe that if you leave a rougher finish this promotes turbulence and better atomisation of the fuel. As you say, as far as port size is concerned it is not a case of having the biggest hole possible...too big and gas speed drops below the optimum and power falls as a consequence...Ian

email (option): julie@wright52.plus.com

Good one ian ,I did suspect you have had good sucess,as i dont know you personally,but have picked up on your knowledge on this forum, and its good to see those who put in the time and effort be rewarded with those sort of results.To smooth or not to smooth ,or how big to make the hole ,is always an interesting topic and yes roger i certainly agree too big is not always the answer.through my own experiences I think it depends a lot on the cam spec and engine internal mods and if the port is opened too much port velocity can be lost which is a step backwards.I have experimented a little with port sizes but generally only clean them up shape wise get rid of some dags and always match ports ,gaskets,manifolds,carbies,exhausts etc to enable uninterupted flows.I finish exhaust ports as smooth as i can to hopefully speed the exit but intake ports i finish with a rougher finish as i think this helps with air/fuel atomisation.Thats what i did to my army m20,and without the real truth of a dyno test nobody would really know,but the ole girl does feel very free on the road and throttle response feels nice . cheers adrian.

email (option): cruiser3@icisp.net

I believe that Wal Phillips fuel injectors are classed as "naturally aspirated " as it still relies on the air flow through the venturi, so this may compensate for the bad port design of the SV engine. I used to help out Pete Williams who was the third fastest in 1968 behind Alf Hagon. He used the Wal Phillips injectors on his test bed engine "Two Faced" and the test bed of "Two Faced + one" for his streamliner 200 mph attempt and I believe that these were classed as naturally aspirated, so could be used to compensate for the arduous inlet tract by maximising its flow, the exhaust port is less significant in its shape, so needs little more than trumpet shaping and the guide cutting down to maximise its flow. Common theory by most of the people who use the flow bench to test the combustion chamber shape that the slightly rough finish (radially, rather than laterally) flows more by creating more turbulance.
The only problem with the Wal Phillips set up is that they are like a switch, either on or off, with not a lot in between!
To further make up for the inadequacies of the inlet port, I'd suggest relieving the inlet guide, not too much of a problem as most of it is below the port anyway, and to make the port as "trumpet" shaped as possible as this allows maximum flow over the seat area as the mixture has reached it maximum velocity prior to reaching the seat rather than trying to maximise the velocity of the mixture on the very point of the seat area (possibly enlarging the port as, using the injector negates the need to have a smaller port to increase the flow over the already oversized seat) Apperently a "D" shaped port around the bend of the inlet port helps too as it maximises the flow (it has been used quite effectively on the bad port shape of Harley Davidsons on their performance heads) on The Harley WR's they used to grind a channel to the ports to speed up the flow to the combustion chamber, but this was because the standard WL had ports that were set in a recess, but on the M20 this isn't a problem unless the valves are well pocketed. As for the cylinder head, it would be best to use a sort of "Riccy Chip" either in the form of a bolt in type or shaping the head by filling with weld to give a more severe angle to speed up the gasses flowing back to the plug after induction, (failing that you could try re-positioning the plug more to the area around the timing plug)
Combine this with the maximisation of compression ratio for the fuel being used) The main problem with SV engines is that after the induction stroke the fuel is compressed and has to change direction to meet the spark plug which is usually positioned over the valves, so the head shape is quite critical to speed up its change in direction to be ignited by the spark plug. Naturally it would be wise to remove as much weight as possible from the flywheel to allow maximum acceleration as the less revolving mass the better. Other things such as lightening the timing/cam wheels should have the same effect, but to a lesser degree. If you weren't too bothered about the appearance of the bike or it's modifications then using the cush drive area of the crank to drive a proper supercharger wouldn't be too hard as the cush drive would be then transferred to the clutch itself by using a Triumph clutch centre (you don't really need one at all but the clutch tends to become "all or nothing" without it) but using lighter flywheels it could become an issue unless you dump the clutch at full revs, using the temporary clutch slip to overcome it. When I used to help out Petes mate on his Jap sprinters we always made the clutch centres solid, but he was usually hitting 10,000 rpm before the clutch was dumped so naturally the clutch would slip slightly until the inertia caught up with the engine

email (option): davmax@ntlworld.com

2 plugs one in the timing hole and one in the normal position with slightly different timing to get the best burn of the air petrol mix this should be easily done with eltronic ignition or does this stray from the original idea ie using a mag just though i would mention turn off the petrol when stopped when using a wal phillips or have a cylinder full o petrol i know i was that soldier

I am intending to 'twin plug' the sprinter by fitting electronic ignition into the mag body. That way a more original look is retained. An added advantage of the electronic ignition is the introduction of a proper advance curve, impossible with a manually adjusted mag. At the very least with a more 'standard' tuned engine and ignition system?..the plug should be repositioned away from the inlet valve.
The optimum position is in the centre of the combustion chamber (not including the part of the piston covered by the head) and with a slight bias towards the exhaust valve. Having (hopefully)improved combustion with cylinder head alterations it is worth experimenting with less ignition advance as a more rapid and efficient burn doesn't need as much.

email (option): julie@wright52.plus.com

Regarding port sizes, if a standard weight crankshaft is used enlargement should be strictly limited.
The basis of tuning these engines, both OHV and SV is to lighten the crank considerably to allow the engine to rev freely and pick up more quickly. This will allow higher lift and duration cams such as Goldie cams, which have far more overlap, to function correctly. High degrees of overlap will not function as intended at low revs.
Take a look at a standard Gold Star crankshaft or any crankshaft from a more modern engine to confirm this.
Quicker crankshaft acceleration also helps gas velocity in the inlet port and helps to maintain this at workable levels with the larger ports required.
All engine characteristics should be focused on optimising gas flow..the more you get into the cylinder, the bigger the bang. Raising compression ratio for example isn't a lot of use if cylinder filling is poor...there is nothing much to compress in that case!!
I cannot stress enough if you are really after power..1)Lighten the crank..2)Concentrate on achieving good gas flow results in conjunction with improved cams, valve sizes etc..3)Run the highest compression ratio you can without inducing pre ignition or compromising (2)....Ian

email (option): julie@wright52.plus.com

Hi boys thanx again,all good imfo, i had actually contemplated super charging and fuel injection,as most s/v engines will respond to this very well, that was until i picked up a period 2 rule book. I have been hunting for a mag housing as i will be fitting elec ign into the housing so things appear to be stock ,and i will definetly be putting the flywheels on a diet though unsure how much at this stage. So as i said ,thanx because i now will be able to put a reasonable plan together,and start hunting parts with more knowledge than before which helps with a base platform on where to start.

email (option): cruiser3@icisp.net

Just resurrecting this topic - for any who might be interested and haven't read it before the Rapid Hare Norton blog has just listed a 1936 article on sidevalve tuning.
http://rapidhare.blogspot.com/

Some more interesting stuff on tuning 16Hs on the Norton blog site.

This is the one that Ian has to beat !

http://rapidhare.blogspot.com/

I'm glad that this bit of info has turned up...I have been trying unsuccessfully to find out what was the maximum speed recorded for Nigels bike. I had heard he had done just over 116mph over the 'flying quarter' and had possibly pushed it up to 121mph. However, as the latter figure was a calculated top speed and not a recorded average speed 117+ remains the target...Ian