The Roy Boys' Engines

10/10/2021

It's been a while! But I haven't quit yet! Just no time!

Valves
A Tech Talk by Fred

Valves are one of those things which are taken for granted, misunderstood, and both over and under invested in. Your aftermarket summit racing supplied iron cylinder heads you’ve been running have valves in them right out of the box. Why bother reinventing the wheel?

Most heads out of the box will come with stainless valves. There is nothing inherently wrong with stainless as a material, it has several desirable qualities, strength being chief amongst them. This is not to say all valves are strong and reliable. Cheap valves should not be trusted unless in stock application, and even then can be problematic to say the least.

Stainless valves are said to run cooler than titanium, due to higher thermal conductivity and therefore are often used in boosted applications where detonation is a concern. However they are heavy. This has led to several innovations, such as gun drilled stems, smaller stems, and sodium filled stems.

Gun drilled stems are hollow like the barrel of a rifle. They are lighter, how much I do not in particular know. They have the reputation of being rather problematic when small diameter stems are used with high spring pressures. In my opinion, they are not the way to go.

Sodium filled stems are gun drilled, then filled with sodium. Sodium is lighter in weight than the same amount of steel. At operating temperature, the sodium melts (208°F) and improves heat circulation through the valve. Sodium conducts heat better than steel does. Imagine holding a long bolt in both hands, same sizes. One bolt is aluminum, one is steel. Now have the end you’re not holding onto heated up. Common knowledge dictates that the hand holding the aluminum bolt will get uncomfortable rather quickly. How does this pertain to the sodium however?

By adding a better pathway for the heat to go through, the heat is transferred further up the stem. This allows more heat to be pulled from the part of the valve which is exposed to the intake air.

The hot end of the aluminum will also be cooler than the steel one is. The hot end is in fact the face of the valve, and the cold end is within the valve guide. A valve only has 3 places for heat to go, into the valve guide, into the valve seat, or into the air stream. We go through excessive efforts to ensure a performance engine is breathing cold air, so why would we want that cold air heated up before the valves are closed? Every BTU of heat you remove from the valve through the guide or through the seat is one less BTU put into the air stream.

In theory, I feel this could lead to a measurable increase (Most would say minor) in horsepower. However, these valves are supposedly VERY problematic. As sodium melts, it will quite obviously expand (Almost all solids expand when turning into a liquid. “But things expand when they freeze! Why do pipes burst when they freeze you du***ss! You must be wrong Fred!” Water expands when it freezes and contracts when it thaws because ice is in fact a crystal. As it freezes, the molecules arrange themselves in such a way that they take up more space than when it was simply a random soup. Water is quite unique in the world.) Since sodium expands when it melts, it puts internal pressure into the stem. A properly done soda valve would be filled in a vacuum and then sealed which would also lower the melting point of the sodium. I do not as a matter of fact know if they do this or not. Also keep in mind that as the valve temperature increases, the sodium would get hotter and hotter, and we all know that as temperature increases, so too does the volume of a substance, increasing internal pressures further. All of this being said, I have yet to try these valves but I am in fact a fan of the idea. I feel the secret is balancing the stem diameter with the flow and expected air density due to temperature climb. Obviously a thicker stemmed valve would be stronger, but it also impedes flow. More research and testing must be done in this area.

Smaller stems are normally the go-to in the performance world. In general they flow slightly more air with all things being equal. How much depends highly upon the design of the bowl and short side turn. In my experience and opinion, a properly designed intake runner will benefit more than a poorly designed runner. Some runners have such poor short side turns right out of the box that there is simply not enough air flow to be impeded by the stem. When the port is properly done it will make use of all available area in the port with a nice smooth taper with the smallest part of the port being just before the seat. The roof of the port where the valve stem and guide boss are mostly influencing will be flowing far more air and therefore benefit the most from smaller guide bosses and stems. This is an efficient port. A truly great port flows quietly and smoothly, and the amount of flow is dictated by size. The size is dictated by the cubic inch and rpm.

Do NOT assume your aftermarket cylinder head to be this good. Hell, don’t assume your ported cylinder heads to be this good.

And finally, titanium valves. Titanium valves are normally reserved for the highest levels of the amateur racer, and considered the bare minimum for professionals. They are very costly for sometimes little to no benefit. The biggest benefit is quite obviously weight. Titanium valves are significantly lighter than the equivalent steel valve. They also conduct heat far less, which can be a positive and a negative. On the positive side, they heat the air less and absorb less heat from combustion. On the negative, they run hotter than steel valves, leading to detonation. This is somewhat confusing on multiple levels, how can they absorb less heat but be hotter? Combustion temperatures as measured from an EGT (exhaust gas temperature/pyrometer) are roughly in the 800-1200°F range as measured from the exhaust manifold. However, peak temperatures inside the combustion chamber are several times higher. They have been measured to be upwards of 3000°F (I believe I remember reading a study done on the matter which said something like 5000°F peak temperature with a relatively high (12:1) compression test engine. But I do not remember exact numbers here.) All parts of an engine come to a certain point of temperature stability when the engine is under a steady state. The amount of heat energy absorbed by the valve must be equal to the amount of energy it gives off to the intake air, valve seat, and valve guide. Otherwise it would continually get hotter ad infinitum. The air is quite obviously the largest cooling factor even if we do not desire it to be. If the valve conducts less heat to the air then the valve will retain that heat and become hotter. A hotter valve has more heat to give off. Therefore the temperature increases until it becomes stable. A hotter valve absorbs less heat from combustion as well, which explains why the operating temperature is higher than that of a steel valve. In hindsight, there should be a much better way to explain that using math. But not everyone understands things through numbers. The biggest point is, different valves run at different temperatures.

And that's it folks. Any questions, comments, leave it below in the comments.

09/13/2021

Points Results are partially in.
1st place goes to John Roy with Never Satisfied
2nd Place goes to Louis Roy with Mad Jack
3rd place should be Jeremy "Bubba" Siebel

Great job this year to everyone who competed.
This marks the 3rd straight year a Roy has won the championship, Lou won the previous 2 years.

When the points placement comes out in it's entirety I will post it.

08/22/2021

Which one are you?

05/24/2021

Any requests for the next tech talk?
Currently writing:
Viscosity (Explanation on oil weights, basically some useless knowledge on oils)

RPM

Porting stages (stage 1 stage 2 stage 3 stage fredneck.) Not a tech talk, just a very basic explanation of what I can do. If you're looking for secrets to do it yourself this isn't that kind of article.

Thinking of writing
Emissions as I know it
Compression ratio (static vs dynamic)
Something with valves?

First one to make a request gets their wish come true

05/23/2021

Do YOU know what the answer is...?

05/22/2021

05/18/2021

Ignition
A Tech Talk by Fred Roy

Ignition is something which I think many people take for granted. As long as the mixture is ignited then there is the mentality that there is not much to be improved upon, or that there is not much to be gained by improving upon it.

First off, this is going to be a very difficult article to write without pictures. Forgive me if some things seem hard to visualize or understand. I am debating on starting to do these talks as video, perhaps Lou would be interested in doing it with me? Shoutout to Lou! And please, by all means hit the share button. The entire purpose of these talks is to advertise our knowledge for the next stage of business.

So, let us begin with, why do we need better spark? Let’s talk about chemistry. I am by no means an expert but I know enough to explain the basic idea. Every chemical reaction needs a trigger of some nature. There are more than a few which spontaneously occur, but in these instances the trigger is something which we cannot control, such as radioactive decay, electron disruption due to high energy photons, etc. For example, nitroglycerine spontaneously explodes… but the bump that caused it gives enough energy to break the very fragile chemical bonds which then set off a chain reaction.

The bonds which hold most fuels typically used in engines are strong enough to be considered mostly stable. It takes a very strong stimulus to cause them to react with oxygen and therefore burn. Some fuels are notoriously hard to ignite such as nitromethane or alcohol.

So what causes us to need a stronger spark than stock? Compression, but not static. Static compression ratio (The one most people talk about because it’s easy to measure.) is only a baseline. Effective compression ratio can and does go both above and below it. For instance, when adding boost to an intake, effective compression ratio can and does double while static stays the same. At peak torque, the effective compression ratio is almost always the highest because peak torque indicates when the engine is filling the chamber the best. So, when the effective compression ratio goes up, what else occurs? The density of the charge inside the chamber when ignition (spark) occurs is higher and therefore more voltage is required to jump across the same spark gap.

There is a direct correlation between the gap between electrodes in a spark and the voltage necessary to jump the gap. This is because when voltage is applied ionized particles are attracted to the anode & cathode (fancy term for positive and negative sides). Until enough ionized particles are gathered to form a bridge between the two points a spark will not occur. The voltage determines how many particles will be attracted. Think of a weak magnet vs a strong one picking up a pile of nuts and bolts. Voltage generally is said not to increase beyond what is necessary to jump the gap because the circuit is completed. I disagree with this statement because it is not hard to envision a stronger spark, but even after saying all this, electricity is not my specialty. I have a saying which has done well for quite a long time: “It’s f*ckin magic!”. If there is not enough voltage to jump the gap then obviously spark will not occur. We can jump the spark gap at much lower voltages in atmospheric conditions, so why do we need such high voltages? For example, when welding I typically use a voltage around 25, but I have turned the machine clear down to 17 when welding sheet metal. At 25v the spark is every bit of an ⅛”.

Swirl. Swirl in the combustion chamber to be exact. It’s a very important part of a successful cylinder head. In any engine the act of the intake charge coming into the cylinder and the act of the exhaust leaving the cylinder impart motion to the charge inside the cylinder. This motion makes horsepower. It is fantastic to make low end horsepower, fantastic to make fuel efficiency and just plain fantastic to have. I will sacrifice some flow to gain swirl if given the choice. There are reasons to reduce the amount of swirl but they are few and far between.

The motion of the charge attempts to blow the spark out. In effect the spark in a running engine looks like a horseshoe- it’s true, I’ve seen some pictures taken in a lab environment of spark in a running engine. Very impressive how far from the plug the spark can travel.

This is why I am not a big believer in for example E3 plugs with their shrouded electrode. All they truly do is keep the spark close to the electrode by blocking the wind, therefore reducing the amount of voltage required. Any gains to be had I THINK are only indicative of a weak system. I have not been able to do the testing on the dyno nor have I seen any thorough testing done to prove my theory however so the jury is still at lunch.

So, aside from compression and turbulence in the chamber, what else complicates matters? RPM!

Rpm reduces the amount of time between spark events, working that single MSD coil to death. Coils work by collapsing magnetic fields. These fields take time to form and time to collapse. As the time is reduced so too is the voltage of the spark. Higher voltage coils therefore increase the voltage at high rpm. A single ignition coil feeding 8 cylinders which is advertised around 40k volts has been measured to give off roughly 8k volts at around 6k rpm. This was either a holley or MSD coil, I do not remember which.

All this being said, why then do I still feel there is room for improvement if the mixture is still being ignited?

Let us go back to the chemical reaction talk. A weak stimulus can still ignite the mixture, but the turbulence quickly relocates the little corn kernel of flame away from the plug and spreads it out. If this kernel is not truly HOT then it has a weak start. If we increase the heat of the spark by increasing the amperage (excess voltage from the coil we can think of as being converted to amperage since it takes X voltage to jump X gap) then we increase the heat of the kernel thereby giving it a fast start.

Spark also has duration. If we increase the duration we elongate the kernel because of turbulence, thereby increasing the flame boundary of the initial ignition event. This also quickens combustion. The faster the mixture burns in a controlled (meaning not detonating) fashion the less spark advance we need to make peak power. Spark is initiated BEFORE TDC. Meaning cylinder pressure rises before TDC, robbing torque and therefore horsepower to fight that pressure on the way up.

Truly the best spark is the one which has the highest energy overall, measured in joules. (Pronounced jewels)

All this being said, if the mixture is being ignited by a good quality system such as MSD, there are no huge gains to be had. Yes I feel there are minor gains there for the taking from different plugs, wires, systems, etc but they do not live up to the advertising put out by the ignition brands in my opinion. When I sit down and experiment, I do not expect more than 5hp on a highly modified engine. Stock or close to it I expect less. Money is far better spent on the airflow of the engine.

So, that being said, what of the wires? Don’t bigger wires make more power?

Yes and no. Generally speaking it takes large gauge wires to transmit large amounts of electrical power. But, the higher the voltage the smaller the wire can be. And to confound matters further, spark plug wires are engineered to have a certain amount of electrical resistance to keep electromagnetic interference to a minimum. EMF causes havoc with ECM’s and any of the computerized items around you, from your cell phone to your pacemaker. In an electronic car, this translates to more power due to less glitches from the computer. In a carbureted vehicle with an old school coil and no radio...no gains to be had from the old school copper wires to my understanding. Supposedly the resistance of the wires causes the coil to create more voltage before the spark occurs, thereby creating a hotter spark. I don’t know if I agree with that..”It’s magic.” All this being said, why then do they sell bigger wires? Most people do not realize that electricity does not flow through the metal part of a copper wire. It actually flows through the magnetic field which is generated when electricity flows. The higher the voltage the larger the field becomes. If the silicon jacket of the spark plug wire is not large enough in diameter then the magnetic field can allow electrical bleed wherever the wire touches something conductive. Larger wires are therefore only larger on the silicone jacket, and only truly prevent problems rather than improve the spark. MANY old time racers whose names I won’t share but who are major winning engine builders emphasize the importance of keeping your wires from touching each other or touching metal parts of the block. In the old days they would very frequently get detonation because one wire touched another, or misfire because the spark bled to the valve cover.. Detonation always hurts power, but it can also hurt your wallet!

At the end of the day, just buy whatever aftermarket you trust and call it a day. Chasing those last few horsepower in this part of the engine should only be done if you're making very respectable numbers (520 CI x 2.1=1092hp) That money is better spent on the heads.

05/13/2021

AFR vs. EGT’s
A Tech talk by Fred Roy

The main topic today will be air-to-fuel ratios, but before I begin I want to mention EGT’s.

EGT’s (Exhaust Gas Temperatures) are found using pyrometers or K-type thermocouples. Usually this is done near the port exit. The very important part is that doing it this way gives us an indication of the EGT from specifically one cylinder. If you wish to compare one cylinder to another cylinder please remember to place them as equally as possible, as even a ½” can affect the readings more than you would expect.

So, what do EGT’s have to do with AFR? A pound of fuel (any fuel, as EGT’s are universally linked to AFR) has a specific amount of BTU’s (British Thermal Units, 1 BTU is the amount of heat energy it takes to raise 1 pound of water by 1 degree Fahrenheit. “But my hot water tank is 30,000 BTUS and I still run out! 458 Lbs of water (55 Gallons)x 60 degree temperature rise (60°F to 120°)= 27,480 BTUs, appliances are rated in BTU’s per hour. So now lets add some flow to the system, a garden hose does about 7 Gal/min so 7gal x 60 min =3498 lbs of water… Not enough BTU’s at all.) Your shower probably does half that, but you get the picture.

Pump Gas 18.7-19.1K BTU’s per pound

Lean mixtures (>14.7:1 on gas, Lambda >1)do not have enough fuel to completely burn all of the oxygen in the mixture. This also means they are like your hot water tank and do not have enough BTUs in the amount of fuel to fully heat the air. Lean mixtures can melt pistons only because the mixture burns far faster due to the surplus of oxygen, thus increasing peak cylinder temperatures. Think of a cutting torch, the same amount of propane will burn red when the oxygen supply is off. But when the oxygen is turned on, it burns far faster. In both instances the propane only has so much heat energy to give off. More likely however is that detonation occurs (lean mixtures are far more prone to detonation). Imagine beating on a 900°+ piece of steel.. Steel begins to glow at 500° so it’s not hard to figure out that detonation causes deformation. This is my theory on the matter however, and I do think both scenarios do occur.. Without concrete data on in cylinder temperatures over crank degrees it is hard for me to say what exactly occurs most of the time when people melt pistons. For fuel efficiency, lean mixtures are generally the goal. But, they are notoriously hard to ignite. Bosch has been working on a laser ignition system for the past several years to cure this problem. In this system a special spark plug is used which is a multi point laser, rather than a spark. This laser is a pulse type and therefore extremely hot- A normal laser pointer is on all the time, but lets take the same amount of energy expended over a minute or more and condense it all into a fraction of a second. This laser technology is in fact what is being used in the prototype nuclear fusion reactors to ignite the fusion process. LOTS of heat focused on a small area, creating temperatures in excess of a few million °F in a fraction of a second. For the record I read a LOT of tech papers because science is kool… Just like pointing a laser through dust or fog shows us the beam (like in the spy movies) the beam ignites the mixture. They were having technical difficulties with keeping the optics alive at high temperature/pressure. Lean mixtures make fuel mileage because at part throttle (99% of a daily driver’s life) the effective compression ratio is a fraction of what it is at full throttle due to obvious reasons (The cylinder doesn’t get to fill up. It’s hard to compress what isn’t there.) Low compression ratios cause lack of efficiency and numerous other things. If we can open the throttle all the way all the time and simply limit the amount of fuel (Much like the operation of a diesel engine) then the effective compression ratio becomes much better therefore improving efficiency. Another side effect of this is actually lower emissions. It is no secret the world is trying to limit emissions (Whether you like or believe in global warming is a different story, but I can talk about that if you want though I am far less educated in environmental sciences.) Having a surplus of oxygen eliminates the need for catalytic converters. It does however create more NOX emissions due to the effective compression ratio which now needs DEF to cure. I am not sure at what compression nitrogen reacts with oxygen forming NOX. However adding EGR systems now lower the NOX emissions because the oxygen dilution slows the burn, lowering peak cylinder temperature and pressure. Perhaps someday I will make a talk on emissions. I do not like emissions systems but they are a necessary evil if our children’s children are to have a future (Look up the average daily temperature in the arctic.) Unless of course you want to ditch your vehicle and ride a bicycle. I’m fat and therefore to hell with that. The systems are very technical, but the method of operation is actually pretty cool.

Stoichiometric mixtures (=14.7:1 on gas, Lambda =1)have exactly enough fuel to burn all of the oxygen in the mixture. Theoretically this means 14.7 pounds of air (1000cu/ft weigh about 75lbs)(14.7lbs=196cu/ft) mix with 1 lb of gasoline in this example. Different fuels have different stoichiometric ratios, methanol for example is 9:1 so don’t lock yourself in. Lambda is ALWAYS stoichiometric at 1 regardless of fuel used. This is why the tuning world usually uses lambda measurements. It's far easier to remember lambda=1 @ stoich than it is to remember all the different air to fuel ratios for the fuels used in the performance world. At stoichiometric ratios we see the highest exhaust temperatures. At full throttle stoichiometric mixtures can and do melt pistons. It is not uncommon to see upwards of 1100°F (I believe I have seen a dyno sheet on the internet at one point showing 1400° but I’m not sure) The other side effect of this higher temperature is more heat making it’s way into the block and head, meaning you’ll quickly boil the antifreeze. Most cars and trucks aim for a stoichiometric mixture or slightly rich for best on-road performance at part throttle (MPG plus drivability, always a tradeoff). The newer the vehicle, the leaner cruising AFR is in general.

Rich mixtures (

05/04/2021

HOT ROD V-8 2021 SCHEDULE

05/04/2021

Tom Kowchek asked for me to talk about the flow numbers on before and after a basic port job. This is a set I did recently to sell at a later date. I removed all the identifying information, but this is the excell spreadsheet I use when I flow test heads. This would be a "stage 1" job. Nothing extreme but there were a few very basic tricks used (worth about half of the improvement and aren't listed in the comments.). Notice that flow rarely improves across the board. Sometimes air does some very strange things. I only did a before and after, no real development work. The seats definitely had room for improvement (you didn't think I learned about airflow without spending DAYS learning about valve jobs did you?) and I have no doubt I could have gotten [email protected]" with a bit more work. For those curious, these heads are BBC, V8 class ready. They will support 600-900hp@6000 depending on the rest of the setup. Knowing these flow numbers and the rest of the eventual combination I can select the camshaft to make peak tq and horsepower where I want it within around 200rpm. I was impressed with them considering what they started as and the minimal amount of work (aside from being iron and therefore a pain to clean up). You will also notice differing results. I did fix the issue but I didn't re-flow it since I knew it was the problem, part of it was the seat getting damaged. Questions? Leave them in the comments.