Precision measuring tools

I bought a Starrett 10 - 11 inch micrometer With a friction spindle and spindle lock Grumpy.
Used and in excellent condition.
Going to use it to Measure Verify the True Deck Height of my Pontiac 455 block for the 1970 Trans Am.
Determine the True Pin setting compression height needed with extra long Ti connecting rods.
Order then my Diamond pistons.
3 week wait to get them.
Custom made to my specs.
 
Its in Very Good condition the Starrett 10-11 inch micrometer.
Graduated in .oo1".
No Standard came with but I found a few online & going to buy soon.
I can give to my friend Bob & he can calibrate at his work in the Machine shop inspection room.
 
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Bronze valve guides Advantages
Manganese bronze works great with higher valvetrain speeds and offers great corrosion resistance.
The material make up of manganese-bronze guides generally consists of 55% copper, 40% zinc and 3.5% manganese.
As far as any other materials used in performance, manganese-bronze is still the best choice for valve guides.
Valve Seats & Guides

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By

Bob McDonald
on

Apr 30, 2013
Most engine builders worth their salt know that with the components and technology available today, it’s not that difficult of a task to make horsepower. With the availability of so many performance parts – whether it’s from the OEM or the aftermarket – engine builders can pull from vast resources to achieve a balance between reliability and horsepower.

Reliable and enjoyable horsepower can be made so easily today that I often think about what it was like, say, ten years ago when it was such a struggle, and an expense to “go-fast.”

With that thought in mind, I sometimes ponder the changes that have taken place in the manufacturing world that put us where we are today. It is not so much as the hard parts such as cranks, blocks, connecting rods and cylinder heads, as much as the different alloys that are being used to manufacture these hard parts, which, subsequently, make power also.

Take cylinder heads, for instance. What changes can possibly be made to them that have not been accomplished already? Yes, the goal is airflow, but high cfm numbers don’t seem so unrealistic anymore. In today’s performance market there is a cylinder head for practically any street application or racing class you can imagine.

There are also CNC programs that are offered by aftermarket companies that can port a cylinder head for, as an example, a late model Hemi. So, airflow through the cylinder head is not really the hurdle it used to be. The challenge now is the valvetrain.

The weight of the valvetrain seems to be where the focus is at the moment. Trying to reduce the mass of the valvetrain while increasing opening and closing rates of the camshaft and trying to keep the valve from bouncing on the seat is not just a hurdle for engine builders and racers, but for the manufacturers as well.

Production engines now make more power than ever while offering considerable fuel mileage with longevity. With this in mind, we can see what materials the manufacturer (as well as the aftermarket suppliers) are using to keep up with today’s valvetrain technology.

Valve Seats

First of all, we’ll discuss valve seats and what’s going on with the changes that are taking place. What is the importance of the valve seat? Let’s think about its job first. The seat has to seal against the valve face in order to achieve the necessary efficiency in the engine. Second, the valve seat has to transfer heat from the valve face. For quite some time now, more than 90 percent of OE applications have used what is known as a powdered metal (PM) valve seat.

PM offers great durability and is a lot less expensive to produce. The great thing about powdered metal is its ability to retain its shape to ensure valve seal along with the ability to remove heat. This comes from how the seat is produced. The process that is used to form the powdered metal seat allows the materials that make up the PM seat to become more uniform. The old process of making a cast seat presented several problems.

According to Chuck Barnett at Dura-Bond Bearings, “When you pour a cast seat, you pour it hot. When poured in liquid form, you get voids from gases plus hard spots.”

Barnett says that cast seats often resulted in uneven mixing of materials and the seat was often not uniform, which made them more difficult to machine. When making a PM seat it’s like baking a cake. All the ingredients are added together and mixed cold. Then the mixture is placed in a press and squeezed by 100 tons of pressure. The rate of 200,000 pounds per square inch makes the material more consistent.

There are different blends of materials that are used to make different types of PM valve seats. Sometimes “softer” blends are created for use in some racing applications to lower valve bounce at higher rpm. This also gives the opportunity to incorporate other materials into the mix when making the powdered metal valve seat such as graphite, which will offer some lubrication.

Dura-Bond also offers a new line of PM seats they call the “Killer Bee” series. This series of valve seats is based on a copper infiltrated design used by GM in the LS3 V8 engine. The process of making this seat is the same as others where the mixture is pressed together. But now a copper wafer is added to the top of the mixture and then sent through a furnace where the copper melts into the mixture.

The molten copper penetrates the seat that results in a 15% copper mixture which offers a 4-6% faster heat transfer from the valves to the head. The Killer Bee has excellent machining capabilities along with reduced wear and superior finish. The Killer Bee series can be used with steel valves only because of the carbide hard phase process. And Titanium valves can be used, but only if they are coated.

Speaking of titanium valves, another choice of seat would be Beryllium copper. This material is noted for high strength and thermal conductivity. The greatest asset would be the ability to remove heat from the valve while taking a beating. Beryllium is only used in extreme racing applications. This is due primarily to the expense: a seat can cost an average of $35 each.

The biggest problem with Beryllium copper is the machining process. Here in the U.S., OSHA limits the amount of time someone is exposed to the material while machining in a controlled environment. When machining, small dust particles are released into the air that when inhaled over a period of time can cause severe lung damage and even death. So, it’s not just the price of the seat but also the price of machining the seat. Ductile iron is also a less expensive choice when using titanium because of its strength and durability.

One thing new for Beryllium copper has been developed by Exceldyne. They have recently developed a proprietary valve seat finish. This new technique improves the Ra of the valve seat while still maintaining the sharp edges that contribute to airflow. This form of finishing technique also promotes coating adhesion, which can now be used to reduce the wear on the copper based valve seat.

When rebuilding cylinder heads, one choice is the use of a high chrome valve seat. These seats work well when repairing OEM cylinder heads. They offer great strength and dependability while being very cost effective. They are easy to machine and offer great longevity when used for applications such as daily driving.

Tungsten carbide is used primarily for diesel applications. The cool thing about tungsten carbide is the more the valve seat is pounded the harder it gets. This is crucial to the life expectancy of the diesel engine. This helps these engines operate close to a million miles or more for over-the-road trucks before a rebuild.

Tungsten carbide is inexpensive to machine and produce, making it very cost effective as well. Dura-Bond manufactures a tungsten carbide seat with special additives that offer high temperature lubricating properties, which is not affected by high heat or machining.

These seats also work well in dry fuel applications such as propane and natural gas. High nickel has been used in propane and natural gas applications with great success. Since there have been more advances made for the use of diesel, propane, and natural gas, valve seat material has to be similar to ceramic in which the seat does not soften at elevated temperatures along with the ability to be machined like metal.

Valve Guides

Valve guides can be generally classified into two groups: cast iron and manganese bronze, which covers a wide range of applications.

Cast iron guides are used mostly by OEMs due to its wear characteristics that result in longevity for high mileage applications. Cast iron is used with chrome valve stem applications as well. Cast iron cannot be used with stainless steel because of its tendency to gall.

That’s why high performance applications do not warrant the use of cast guides due to the fact the material can’t handle the high loads associated with higher spring pressures. Under high stress, cast iron guides tend to crack and fracture, which can result in engine failure altogether. Cast iron is inexpensive and works best with daily drivers and high mileage applications.

For any kind of performance application, the choice is manganese bronze. The way to pronounce this correctly is MAN-GA-NESE. I often hear this as magnesium, which is not correct. Manganese bronze is ideal for performance because it is more compatible with titanium and stainless steel.

It has the ability to handle high stress loads with some lubricity, and the ability to have tighter tolerances with great heat transfer. Manganese bronze works great with higher valvetrain speeds and offers great corrosion resistance. The material make up of manganese-bronze guides generally consists of 55% copper, 40% zinc and 3.5% manganese.

As far as any other materials used in performance, manganese-bronze is still the best choice for valve guides. One thing that has evolved with the material is the way that it is being machined today. Precision Engine Parts (PEP) now offers their manganese-bronze guides with an internal groove.

This internal groove provides the intrusion of a small amount of oil into the guide area for added lubrication. This is used mainly in endurance applications. This high-quality material is manufactured in Germany and machined here in the U.S. by PEP.

Another added feature to manganese bronze guide was introduced by C.H.E. Precision Machine. C.H.E. integrates an internal O-ring into the guide instead of using an external valve guide seal. This was done because of the increased valve lifts in performance.

Valve lifts as high as .900? are becoming common in class racing. This style of guide with an external O-ring is beneficial because of the time it takes to reach these kind of valve lifts where triple valve springs must be used, which limits room for the valve stem seal. By being able to remove the seal, more length can be added to the guide allowing more stability in the valvetrain.

One more new thing to the market is the introduction of the high-temperature copper-bronze valve guide by Ferrea Valves. This is a proprietary heat treatment of the copper-bronze alloy that so far has better heat-resistance, lubricity, and the material has the ability to increase the heat-dissipation.

These copper-bronze valve guides are CNC machined and concentrically ground, which allows the tolerance range to be taken within .0005?. These valve guides are now being offered for domestic, import, and motorcycle applications.

Like I mentioned earlier, the primary focus of making power is to reduce the mass of the valvetrain. The reduction in valvetrain weight seems to be making big gains in finding more horsepower. This practice is becoming more common from racers to professional engine builders, to the OEM and aftermarket manufacturers.

For suppliers of valve seats and guides, visit our online buyers guide. Special thanks to the following for their input: PEP Precision Engine Parts, Dura-Bond Bearings and Ferrea Valves.
 
https://www.enginebuildermag.com/2009/11/valve-and-guide-material-selection-update/

Valve and Guide Material, Selection Update
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By

Brendan Baker
on

Nov 2, 2009
Today’s engines are being designed with more valves per cylinder with smaller valves to reduce valve train weight and increase intake volume. Cylinder heads typically require valve guide and seat work to restore compression and oil control if you are rebuilding the heads.



For the valve to seat properly and to gain the most power and efficiency, engine builders must replace or bring back to spec all valves, seats and guides. Drilling, reaming, replacing valve guides, removing worn, loose or damaged valve seats, cutting new seat counterbores and machining valve seats are all part of the reconditioning process that your shop must be able to handle with precision and accuracy.



If selling an engine with new performance cylinder heads, some builders buy the bare castings and install their own selection of springs, valves, guides, etc. to fit their customers’ needs. We talked to several suppliers and manufacturers about choosing the right valves and guides for your next engine build.


Designs

Intake valves are typically heavier than exhaust valves because of their larger head diameter. Consequently, the weight of the intake valves is more of a limiting factor on the rpm potential of the engine than the exhaust valves. Even a few grams less weight can make a significant enough difference if the engine revs up to 9,000 rpm.



Many valve manufacturers today are taking some of the heft out of intake and exhaust valves by using hollow stem valves. Hollow stems are created by gun-drilling and micropolishing to make it hollow, similar to a pushrod. The drilling is only done in the upper 2/3 of the stem where rigidity doesn’t matter as much as it does just above the valve head. After the stem has been drilled out, a hardened tip is welded onto the top of the stem. The result is a valve that is about 20 percent lighter than a valve with a solid stem.



Valve stems are getting thinner, according to most experts. The 5.5mm, 6mm, 7mm and 8mm sizes are quite common these days even on domestic applications, says one valve supplier. Nitriding valves instead of chrome plating is also becoming more widely used in domestic applications. Chrome plating is still being used on the heavy-duty side.



Nitriding is a hardening treatment that, even though not as widely used as chrome coatings, has several benefits and is becoming very popular, especially for European and Asian engine applications. The microhardness is higher than the stainless steel base material, which is typically 21-4N, keeping good ductility beneath the hard nitrided layer (microhardness is 800HV minimum). The surface finish is smoother than with chrome stems, creating less friction between the stem and guide.



The nitrided valve seat surface is harder, lasting longer with unleaded fuels, alcohols, nitro or other exotic blends. Nitrided valves match well with any type of seats such as nodular iron, powdered metal, hard aluminum-copper or beryllium-copper seats. Higher rpm engines can benefit from all of the features of a nitrided valve as the nitride layer is applied at a microscopic level so it doesn’t flake or break if a valve touches a piston. The nitride is applied to the entire valve whereas chrome coatings are only applied to the stem.



Are reclaimed valves still a viable option for production rebuilds? Some experts say that it is better to use new valves as the price has dropped for replacing them and you know the material quality probably won’t be an issue. However, according to one expert, reclaiming valves is very popular, especially abroad, where availability often plays a role. This is were the guideliner comes in very handy due to the fact that an 8mm liner fits an 8mm Toyota, 8 mm Mazda , 8mm VW, etc.



Yet another opinion from one of our experts is that reclaimed valves are not a viable option, even more so today with the ever changing fuel environments they are subjected to, including ethanol, CNG or alternative fuels in general.

Materials

Exhaust valves are typically made of 21-4N, 23-8N for many performance applications. These materials are austenitic, nitrogen-bearing chrome-nickel alloys possessing excellent high temperature strength, hardness and corrosion resistance to combustion products. Inconel is another material called a “superalloy” that is often used in exhaust valves where there are very high temperatures. Its use is growing among turbo and supercharged applications. Stellite facing alloys are being used in high heat, high combustion applications such as CNG, marine and also turbo diesel applications.



In the later applications, exhaust materials are being used with facing alloys on the intake. The New EGR requirements on the heavy-duty side have driven this due to the excessive heat, new low sulfur diesel and changes to fluids and oils. On the intake, traditional intake materials are still being used with normally aspirated and some turbo applications. These alloys are typically Silchrome 1 (Sil 1) and 8645H.



For many late model and performance engines, the intake valves are made of an alloy called Sil 1 that contains 8.5 percent chromium. However, the type of material you should choose depends on the application and temperatures. It starts from low-alloy steels Sil 1 to medium-alloy steels (21-2N, 21-4N, 23-8N) and superalloy steels with high nickel content (Inconel, Nimonic). Experts say new alloys being developed include proprietary combinations of nickel, chrome, molybdenum, etc.



In 2-piece diesel exhaust valves you used to see more SAE HEV3 (Inconel) being used, but since this is a nickel-based superalloy and not a steel, the price of nickel has encouraged many valve manufacturers to substitute other materials for Inconel. Some promote Pyromet (also a nickel-based superalloy).



Others use SAE EV16 (23-8N). The appropriateness of the substitution depends on the application and the fuel (CNG, LPG, etc). The problem is that the magnet trick (checking for magnetism in a diesel exhaust valve head) doesn’t tell you anything since austenitic steel and nickel-based superalloys are all non-magnetic.

Guides

Cast iron is still widely used, however experts say new proprietary cast iron materials are popping up everywhere in order to combat the wear encountered on engines such as heavy-duty diesels. With these engines, the EGR applications, low sulfur diesel and lubricants have driven this trend. Powdered metal versions are becoming widely used in heavy-duty also.



These powdered metal (PM) versions are also proprietary materials. Special coatings such as phosphate and added heat treatments are also becoming the norm for the heavy-duty side, says one supplier. On the automotive side, PM is widely used as well as cast iron. Bronze valve guides are still widely used in European applications.



Experts say substituting another valve or guide just because it is the same size is not the way to go. There are reasons that the materials were selected for use at the OE level. They were designed to handle the environment that may be unique to a specific application. Just because it works on one, does not mean it is designed to handle the environment of another.


Liners

According to one valve guide supplier, guideliners that are made of a phosphor bronze have excellent lubricating properties. He says that his company offers a coated liner that has a Teflon-like coating. The flexibility of the liner makes it a very fast, cost-effective way to repair guides. When looking strictly at liners it becomes a lot easier. The liner is very compatible with chromed, non-chromed, nitrided or coated valves, any of these will work, in general, with all fuel applications. This gets a lot more tricky when combining cast guides with the right stem finish and the right fuel application.

Conclusion

Today the technology available to engine builders allows you to, at minimum, duplicate the life of an engine. In order to reach these quality levels (e.g., a rebuilt engine that has the same guarantee as an original one), components such as valves and guides must usually be replaced with new ones and not used or reclaimed ones. But there are some applications where reclaimed components make sense, such as when parts are not available otherwise or cost is a factor.



Experts caution that just because it fits doesn’t mean it’s the right part for your application. Hardness changes with operating temperatures. Mat-erials that are harder at exhaust temperatures may be softer at intake temperatures. That’s why at least keeping the OEM material specification is very important. Improvements over the OEM materials are offered by some reputable aftermarket manufacturers and suppliers.
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Installing Valve Guide Liners

The first step for installing bronze guide liners is to assemble the parts for the boring reamer. Install the bushing, then the spring, and finally the retainer. You now have a reamer kit. Insert the reamer kit in an air/electric drill. The proper drill should not exceed 1,000 rpm under load. Next, choose the appropriate 60° seat collar for your application and install it on the reamer bushing. Insert the reamer pilot into the valve guide to be bored, and hold the seat collar down on the valve seat.



Note: Cast iron guides are bored dry.



Raise the boring reamer off the valve guide slightly, start the air drill, and bore the valve guide. Boring time should be 5 seconds or less.



If you hear a “rumble” during the operation, this is “chatter.” To eliminate chatter, just push a little harder. Bore all guides, and blow away the chips.



Once all the guides are bored oversize, turn the cylinder head over so the “spring side” is up. “WET BRUSH” each bored guide with a nylon brush and a lube (Cutting & Tapping Fluid works well). Spray the brush approximately 1 second and clean each guide. Repeat for each guide.



Insert the auto-driver in a “short stroke” pneumatic hammer (more than 3000 blows per minute, and set the regulator to about one-half power. Insert a bronze-liner on the auto-driver so that the “Speed-Lead” end will be inserted into the guide first, then install.




Note: The auto-driver will install the bronze-liner “FLUSH”. This operation should take between 3-5 seconds.

If you have chosen a bronze-liner that is longer than your application, the excess length will be protruding from other side and must be trimmed off. This operation is generally performed after the sizing operation, as the bronze-liner will grow slightly.



Caution: Distortion will occur on the bronze-liner if too much power is used during the installation operation. This will make the sizing operation difficult.



Using the carbide sizing ball install the ball driver into a “short-stroke” pneumatic hammer and adjust the power to about one-half. Select a carbide sizing ball .001? larger than the desired finished size and set it on top of the guide. With the pneumatic hammer in one hand, use your other hand to hold the tip of the driver with your finger and thumb. Then, with slight down pressure, start driving the ball. Once the driver tip is inside the guide, release the driver with your fingers and move your hand under the cylinder head and catch the ball when it comes out of the guide.



Note: Before sizing the next guide, trim the first one to length and check the “fit,” using the appropriate size valve. Use a larger ball, if necessary, and repeat the process. When the desired size is achieved, size the remainder of the guides.

We suggest having several different sizing balls on hand, as there will always be a fluctuation in valve stem dimensions. After all the guides have been sized, the excess length must be trimmed off.



To trim, insert the appropriate pilot into the trimming tool. Install the trimming tool into a 500 rpm air drill, and trim off any excess material. If a “burr” is created during this operation, it can be removed with the chamfer tooll that has been installed in a “T” handle.



As a final step prior to assembly, it is recommended that the bronze-liner be brush-honed. This increases the surface finish, which gives the guide greater oil retention. – Source: Goodson.com
 
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AUTOMOTIVE
https://www.tomorrowstechnician.com/valves-seats-theres-more-than-meets-the-eye/

worth watching, just for the tips on new head inspection

Valves & Seats: There’s More Than Meets The Eye
The valves and seats in an internal combustion engine play a central role in engine breathing, compression, performance and longevity. It doesn’t matter if an engine has two, three, four or even five valves per cylinder or if the engine is gas or diesel because the valves all do the same thing: they open and close to allow air into the cylinders and exhaust to exit the cylinders.




By

Larry Carley
on

Mar 28, 2016

The valves and seats in an internal combustion engine play a central role in engine breathing, compression, performance and longevity. It doesn’t matter if an engine has two, three, four or even five valves per cylinder or if the engine is gas or diesel because the valves all do the same thing: they open and close to allow air into the cylinders and exhaust to exit the cylinders. When the valves are closed, they have to seal tightly to prevent compression losses otherwise the engine will misfire and lose power. Even though the basic task is relatively simple, the effect that valves and seats have on compression, power, fuel economy and emissions is enormous.

A single valve that is leaking compression can cause a significant drop in power – up to 25 percent in a four cylinder engine! It doesn’t matter if the compression leak is because the valve is bent, worn, eroded or cracked, or if the valve face or seat are not concentric or are out-of-round, the end result is still the same.

These kinds of problems can be avoided by carefully inspecting all the valves before reusing in a stock engine rebuild. The temptation is to save money by reusing and reconditioning as many of the original valves as possible. Valves that are bent, cracked, eroded or have excessive stem wear obviously need to be replaced.

New valves are available from a variety of sources. Stick with a brand name supplier who has a reputation for quality and consistency. Some cheaply made offshore valves are not reliable products because of questionable metallurgy, dimensional accuracy or stem finish. Just because a valve looks good doesn’t mean it is the same as an OEM valve or a quality aftermarket valve.

Remanufactured valves can be an economical alternative to new valves if cost is an issue, especially in diesel engine applications. Worn valve stems can be re-chromed to restore stock dimensions, or the chrome plating can be built up to oversize so worn valve guides can be reamed out to accept oversized valve stems.

Valve stem wear is very common in high mileage engines regardless of whether they are gas or diesel. The factory flash chrome plating on many valve stems is not very thick, only about 7 microns, so it doesn’t take a lot of wear to rub away the chrome plating. Stems can also develop a lobe-shaped wear pattern depending on how much sideways thrust they experience inside the engine. Too much stem-to-guide clearance is not good because it allows the valve to wobble every time it opens and closes. This, in turn, can cause the valve head to flex when it closes against the seat. Over time, the constant flexing can lead to metal fatigue, cracking and valve failure.

Stem finish is important on a valve because if affects friction and wear. Smoother is usually better. Chrome plating is a good material for wear resistance, but so too are many of the new “high tech” PVD, DLC and moly-based coatings.

One new technology we’ve seen is a stem finish that has small wavy grooves machined into the surface with a polymer filling to retain oil. The “snakeskin” finish is said to reduce friction while increasing wear resistance with no change in stem tolerances.



Preventing Valve Problems

Valve-related failures are often blamed on factors like detonation, poor quality or defective parts, over-revving the engine, or the end user failing to set or maintain proper valve lash, etc. Many of these things can contribute to or even cause valve failures, but so can sloppy machining tolerances.

The concentricity of the valve seat with respect to the valve guide and valve is essential for proper alignment and a tight compression seal. Accurate seat refinishing requires a valve-and-seat machine that is in good condition and can hold tight tolerances. You can’t have a couple thousandths of an inch of slop and expect the valves to seal tightly. The pilot-to-guide clearance should be .0002˝ or less for accurate machining. One way to achieve that is to use a high-pressure lubricant on the pilot.

The seat cutter must also be sharp and spun at a high enough speed to produce a high-quality finish on the seat. If you’re getting chatter while cutting a seat, the problem may be too much play between the pilot and valve guide, the speed of the cutter, or the machine is out of level. Using a coolant when cutting hard seats will reduce chatter.

How well the valves and seats are mating after both have been machined can be easily checked using a hand pump to pull vacuum on each of the head ports with the valves in place. If there’s full contact between the valve face and seat, the port should hold vacuum. If you can’t pull vacuum on the port, the valve and seat are not concentric or are not making full contact all the way around. You need to correct the problem before the head or engine go out the door. Hand lapping the valves to the seats can help improve a marginal seal, but should not be necessary if the valves and seats were machined accurately in the first place.

Some production engine rebuilders as well as custom performance builders use a Spintron machine to check compression and valvetrain operation in a newly assembled engine. A Spintron uses an electric motor to spin the engine as if it were running. The RPM can be varied as needed all the way up to redline. The software and instrumentation on the Spintron monitor what’s happening with the valvetrain so any problems that might affect the reliability or performance of the engine can be detected and corrected before it leaves the shop.


The higher the nickel content of the valve, the more expensive the alloy, and the more heat it can safely handle in a racing environment.



Valve Types & Materials

For stock gasoline engines, some type of one or two-piece stainless steel alloy is typically used for original equipment valves. These include “NV” low-alloy and “HNV” high alloy intake valves, “EV” austenitic exhaust valves, and “HEV” high-strength exhaust valve alloy. The exhaust valve has to withstand much higher temperatures than the intake valves so they are usually made of a stronger high temperature alloy.

Most aftermarket performance valves are 21-2N or 21-4N stainless alloys, although some suppliers also offer a 23-8N alloy valve or their own proprietary alloy for high temperature exhaust valve applications. There’s a lot of secrecy regarding the specifics of some of these alloys, but we can tell you that 21-2N stainless steel contains 21% chromium and 2% nickel. 21-4N has the same chromium content but contains almost twice as much nickel (3.75%) for greater heat resistance. The 23-8N contains 23% chromium and 8% nickel. The higher the nickel content, the more expensive the alloy, and the more heat it can safely handle in a demanding racing environment. Valves made of 21-4N can handle temperatures up to 1600 degrees F.

For more demanding applications (engines with nitrous oxide, turbochargers or superchargers), a higher temperature super alloy such as Inconel 751 or Nimonic 80A could be used. Inconel includes a range of high temperature alloys that generally contain 15% – 16% chromium and 2.4% – 3.0% titanium.

One aftermarket cylinder head supplier told us that they use 21-4N intake and exhaust valves in all of their cylinder heads from street performance to all-out big block race heads. “The valves have a smooth finish with chrome plated stems and are used with ductile iron valve seats. We’ve seen no problems with valve durability using these parts, but we do offer upgrades if a customer wants Inconel exhaust valves or light weight titanium valves (which also require copper valve seats).”

Titanium valves are an expensive alternative to stainless steel valves but are one of the best upgrades anyone can make for high RPM valvetrain stability and performance. Titanium reduces the mass of the valve by nearly 40 percent, which means you can use much less spring pressure for the same engine speed, or more RPM using the same springs as before. Reducing the weight of the valves increases spring life, and reduces the stress on the rockers, pushrods, lifters, cam and cam drive.

How well do titanium valves hold up? They are used in some production engines like Corvette Z06 and ZR1 so there’s no question about the ability to hold up under prolonged street or racing conditions. For wear resistance, titanium valves may be coated with a variety of materials including yellow titanium nitride (TiN), moly or chrome nitride. The coatings reduce friction, help dissipate heat and improve the surface hardness and wear resistance of the valve.

Titanium valves tend to hold more heat than stainless steel valves so they require upgrading the seats to some type of copper alloy. Copper provides good thermal conductivity to pull heat out of the valve when the valve is closed. For many years, copper-beryllium alloy seats were used with titanium valves. Copper-beryllium alloys typically contain less than 3% beryllium. Even so, beryllium dust is dangerous and requires special precautions when machining seats. Using a cutting oil or coolant is recommended along with an OSHA-approved dust mask.

In recent years, beryllium-free copper alloys that contain extra nickel and silicon have been developed that deliver the same performance without the health risks. Moldstar 90 is a beryllium-free copper alloy that can be used with ANY type of valve (titanium or stainless) or any fuel where high heat transfer is desired.

If a customer can’t afford titanium valves, another way to reduce valve weight significantly is to go with hollow stem stainless steel valves. Hollow stem valves can reduce weight 10% or more to achieve some of the same benefits as titanium valves without the cost. To improve cooling, the hollow stems on exhaust valves may be partially filled with sodium. Sodium melts at 200 degrees F and improves heat flow up through the valve stem 40% or more. This helps pull heat away from the head of the valve for longer valve life and greater reliability. It also allows the engine to handle more heat and spark advance.

CAUTION: Sodium is highly reactive when it comes into contact with water. If a sodium-filled valve is cracked and is placed in an aqueous cleaning tank, the sodium may fizz out of the valve or even make the valve pop and crack in two.

Sodium-filled hollow stem valves are a good performance upgrade, but we’ve heard of some valve failures in certain production engines that are using these valves. If you surf the Corvette forums, you’ll find numerous posts talking about low mileage exhaust valve failures with the factory sodium-filled hollow stem valves. Some have blamed the problem on a quality control issue with the valve manufacturing process. There are photos of valves that have been cut open that reveal the center hole was drilled considerably off-center resulting in inconsistent wall thickness with one side being much thinner than the other. Some of the hollow stems also show scoring inside from the drilling process, which creates stress risers that can lead to cracks and valve breakage. That’s why it’s essential to carefully inspect every valve for cracks before it is reused regardless of its mileage. Others have blamed the valve failure problem on valve seat concentricity issues, excessive valve guide wear or poor control of stem-to-guide tolerances from the factory. Excess guide clearance allows the valve to wobble and flex with every valve cycle. Some Corvette owners have replaced their stock guides with aftermarket bronze valve guides.

In diesel engines, Stellite faced valves are often used to handle high exhaust temperatures. Stellite may also be used on the intake valves, too. Stellite is a cobalt and chromium alloy that increases the surface hardness of the valve face to about 55 to 59 Rockwell C. A thin coating is applied to the seat area of the valve and valve tip (the valve is usually a 21-4N stainless alloy or similar material). The Stellite coating greatly improves wear resistance at high temperatures. If you are rebuilding a diesel engine that is factory-equipped with Stellite faced valves, use the same type of replacement valves, never ordinary valves.

Valve Seat Materials

Valve seats have to be compatible with the type of valves in the engine. With most cast iron heads, the seats are integral and induction-hardened for wear resistance. With aluminum heads, the seats may be some type of cast iron alloy, powder metal or high copper (for high temperature performance engines or titanium valves).

Valve seat suppliers offer a variety of seat materials, so work with your supplier to determine which alloy is best for the engine you are building.

A high chrome alloy iron alloy with a Rockwell hardness of RC40 should be more than adequate for your typical unleaded fuel gasoline engine, stock or performance. This type of alloy holds up well in applications with exhaust temperatures up to 1150 degree F.

For natural gas or propane fueled engines, or turbocharged, supercharged or nitrous motors, a higher temperature nickel-based alloy would be recommended. Such a material can handle exhaust temperature up to 1600 degrees F.

For applications where additional high temperature wear resistance is required (like a heavy-duty diesel), a Stellite faced seat alloy might be required.

Moving on to powder metal (PM) seats, these are used as original equipment in many late model gasoline (and some diesel) engines. The car makers like PM seats because they are less expensive than alloy seats, can be molded close to finished dimensions, and are easy to machine (when new). PM seats work harden as they age, which is good for wear resistance, but it also makes the seats more difficult to machine if the seats need touching up at a later date. PM seats can be replaced with the same, or with cast iron seats or other alloy seats if desired.



Valve Seat Installation

The big question here is how much interference fit should you use when installing a new valve seat? The seats in some OEM heads may have as little as .002 inch of interference fit – which is enough when you are working with brand new heads and new seats. But more interference fit is usually needed in high mileage heads or ones that will be subjected to high horsepower levels. A common recommendation for installing new seats in used heads or aftermarket performance heads is .005 to .006 inches of interference for aluminum heads, or .003 to .005 inches of interference for cast iron heads. Additional peening or staking of the seats should not be necessary if the correct amount of interference fit is used.

To make installation easier, preheat the heads in an oven to about 200 degrees F (no need to go any hotter), and chill the seats in a freezer. Also, make sure the seats have a chamfer on the bottom outside edge and use a lubricant if the seats are a tight fit. Use a pilot and guide when installing the seats so they go in straight and don’t cock.

Valve & Seat Refinishing

The angles on the valve face and seat can really make or break an engine’s performance potential. A single 45 degree angle cut on the valves and seats won’t provide the same airflow, throttle response and power as a three angle (30-45-60) performance valve job, or four angle valve job or a 45 degree seat with a radius undercut.

There are a lot of variables that influence airflow through the port and bowl area of a cylinder head. Valves with undercut stems just above the head or smaller outside stem diameters theoretically improve flow by reducing restriction in the valve port. However, they may or may not actually deliver a measurable gain in power over an ordinary valve with a straight stem. The same goes for valves with a swirl polish on the top of the valve head, a tulip-shaped head or a tapered stem just above the head. Sometimes these “enhancements” improve power and sometimes they don’t. Every engine responds differently so there is no pat answer as to what type of valve always delivers the best performance.

We don’t have the space here to dive into the theory of airflow except to say that a well done high performance valve job with the right valves and angles for the application can make a big difference in throttle response and power. Get it right and your customer will love the results. Get it wrong, and the engine will never perform up to its full potential.

Maximizing airflow in CFM on a flow bench doesn’t guarantee peak power and performance. In fact, too much airflow can actually hurt power and throttle response because of reduced air velocity. The goal is to optimize airflow in the RPM range where the engine benefits the most. Finding the optimum valve and seat angles often takes a lot of trial-and-error experimentation.

Courtesy Engine Builder.
 
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