Posts in the Tech Notes category
By Dave Monyhan
We're getting close to the end of our series on Rod & Piston Work. So far we've talked about Connecting Rod Basics, Measuring, Machining and Removing & Installing Pins and Bushings. In this edition of Tech Notes, we'll be looking at Piston Ring Fitting. A lot of science goes into the design and manufacture of piston rings. We don't have the time (or room) for that in this post. We will, however, try to get a piston ring expert to share some of his knowledge with us in the near future.
Okay, we all know that piston rings and pistons have always been a part of the internal combustion since its inception way back in the 1800s. We also know that piston rings are designed to seal the cylinder to create compression so the ignition can light the air fuel mixture. And we know that the piston and the cylinder wall must have a specific clearance for oil.
But what about the piston ring? Why can’t you just take them out of the box and put them on the piston and finish assembling the engine? Well actually you can take the piston ring right out of the box and yes, you can install them on the pistons and yes, you can then finish assembling the engine and for the standard “stock” or “grocery getter” engine you will probably be just fine. However that theory will only work for the older style cast iron engines with standard oversize bores. For example, a Small Block Chevy has a 4” bore. If you bore and hone to .030” oversize, the out of the box ring and piston set will not have to be end-gapped. I do recommend, though, that with every engine job you check everything including ring gap even for a stock or grocery getting engine.
But, if you are doing any kind of performance work or adding custom pistons with file-to-fit rings or varying bore sizes you must file to fit. Also if you are changing the fuel delivery system from carburetion to fuel injection, adding nitrous, blowers or turbos then YES, you need to file to fit the piston rings. It is essential that you follow the ring gap directions supplied with your piston and ring packs when you buy them.
What about piston ring gap?
The standing theory is that the piston ring gap is supposed to be .004” for every inch of cylinder bore diameter. We all knew that from high school auto shop.
So how do you file a piston ring to the proper gap?
Chart courtesty of Mahle-Clevite.
Goodson Manual Piston Ring Grinder (PRF-500)
Goodson Manual Piston Ring Grinder (PRF-250)
Goodson Powered Piston Ring Filer (PRF-812DW)
At Goodson we offer both manual and electric piston ring filers. But, before you can gap the ring you need to first…..square the ring in the bore. I recommend our newest Ring Squaring Tool (photos below). The squaring tools come in a variety of bore sizes and have a range of .300” of an inch per tool.
Once the ring is squared in the bore and you have the correctly measured how much material you need to remove from the gap, it’s time to load the piston ring into the ring filer. I will show the electric piston ring filer as an example.
We also need to deal with any “burrs left on the ring gap by using the de-burring wheel on the right side of the PRF-812DW
So as you can see piston ring gaping is very straight forward and actual pretty simple with the correct tools.
Like any procedure there can and will be exceptions so if you get in a bind just call the Goodson Tech Department (800-533-8010) and they will help you fully understand this A to Z procedure.
We’ve spent the past few weeks talking about measuring and machining connecting rods but we may have put the cart before the horse. This week we’re going to correct that by talking about removing and installing piston pins and bushings.
In order to prep your con rods for machining, you will need to have a few items. First, you’ll need a shop press. Goodson Tech Services Manager, Erik Shepard, recommends when looking to add a shop press ask yourself a few questions.
- What’s your budget?
- What do you plan to do with the press?
Erik said, “Usually when someone gets a press, they find all kinds of things to use it for. From pressing out pins and bushings to straightening pieces, etc.”
- How strong of a ram do you need?
For pressing piston pins and bushings, you’ll need a minimum of 5 tons of pressure, but you’ll probably want to go up to 20 to 30 tons if not higher, depending on what you plan to do with it.
- How much room do you have for a press?
Presses are available in lots of sizes from bench-top units to large free-standing ones. Depending on what you plan to do with the press, you will also need room around the unit so keep that in mind when choosing a press.
- What’s your power source? Is it hydraulic or air over hydraulic? Both have their advantages and disadvantages.
For pressing piston pins and bushings, you’ll need a minimum of 5 tons of pressure, In our experience, most pins should break loose at 1800 to 2200 PSI. If you’re still running into resistance at this point, you have other problems. If all you’re going to do with the press is work on con rods, you can use a bench-top model but as Erik said before, you’ll probably find all kinds of uses for a press. He also added that you need be sure it is rigid and durable. Look for quality welded joints and heavy gauge metal. When deciding which press to add to your shop, you will also want to check out the machine’s warranty. Remember, a shop press is as important an investment in your business as any of the other shop machines you use.
Now that you have the press, you’ll need some fixtures and tooling with which to work. Goodson offers several units for piston pin pressing and for pressing pin bushings, particularly tapered pin bushings. We’ll look at each one separately.
Piston Pin Removal & Installation Fixture (PPE-7082)
This fixture is composed of several parts that combine to take some of the guess-work out of removing and installing interference fit piston pins. It was designed to protect high dollar pistons from damage since the piston itself is NEVER under pressure. One of the key features is a series of support inserts that you use to keep the connecting rod aligned properly. Several standard sizes are available, plus one that is ready to be machined to your exact needs. For a complete run down on how to use the Piston Pin Removal and Installation Fixture, check out the product instructions.
In addition to the standard instructions, Goodson Techxpert, Chris Jensen gives these key tips:
- Use the fixture with the press plates that came with your press
- Always select the proper insert. Be sure it fits the piston and pin properly
- Always use Press-Fit Lube (Goodson PFL-200) during the removal and installation process
- Verify alignment, verify alignment and verify alignment
- The piston must float during installation
- The rod must be centered on the pin for proper installation
One last warning that applies with all of these operations: If you run into excessive resistance, do NOT keep applying pressure. You can easily cause damage.
Universal Piston Pin Press-Out Tool (PPE-1)
A universal tool set to use with your shop press, this tool is made of high quality steel and is sized to work with most applications. This set is for basic removal of pins without damage to the piston. Using the Piston Pin Press-Out Tool is pretty self-explanatory, but you can check out the product instructions for more details.
As with the Piston Pin Removal and Installation Tool, always be sure to use correctly sized support fixtures, use press-fit lube and verify your alignment to avoid damage to the work piece.
Universal Tapered Pin Bushing Press Kit (TB-KIT)
One of our newer additions to this class of tooling, the Universal Tapered Pin Bushing Press Kit is designed to work on common light to medium duty diesel applications. It can be used to remove and install tapered pin bushings.
When asked why a shop should invest in the Universal Tapered Pin Bushing Press Kit, Erik Shepard gave these five points:
- It’s the best tool for removal and installation for tapered connecting rod bushings up to 2″ in diameter.
- The tool is designed to prevent piston damage during use
- With the number of bushing drivers included in the kit, it can accommodate many sizes of tapered rods
- Specially sized bushing drivers can be made to order
- You never have to make-do with different methods when installing or removing tapered bushings.
For more specific information, check out the product use instructions.
As always, if you have any additional questions about these or any Goodson products, contact the Goodson Techxperts by email or call 1-800-533-8010.
Over the past few weeks we’ve been talking about Connecting Rod Reconditioning in Tech Notes. Thanks to our friends at Sunnen® Products Company, we’ve been able to share material from their book, Sunnen’s Complete Cylinder Head and Engine Rebuilding Handbook. Unfortunately, this book is now out of print. If you’re looking for a copy of the book, they’re pretty scarce but you might be able to find one on Amazon or eBay. We also did a short search and found that it is available as an e-book, but a membership is required in order to read or download the text.
As we move into our last section on Connecting Rod Reconditioning there’s a lot to cover. If you’ve been working on engines for any length of time, you already know most of it. With that in mind, we’re just going to cover a few basics here and give you some links to additional resources.
Cap and Rod Cutting
As we’ve talked about in previous articles, all connecting rods have a parting edge. Most are flat surfaces machined into the cap and rod sections. These surfaces must be straight and perpendicular to the rod sides. If they aren’t, cap misalignment can reduce clearance between the rod and the crankshaft journal.
In most rebuilding cases, you will remove .003” (0.08mm) from each mating surface for a total of .006” (0.15mm). This small of an amount of reduced center-to-center distance won’t interfere with the compression ratio significantly and general doesn’t compromise the deck-to-piston clearance; even when the deck is resurfaced.
You will, of course, need to remove rod bolts when getting ready to work on the mating surfaces. To do this, you will probably need a press and disassembly fixture. Be sure the surfaces are clean as well before doing any machining.
A Few Important Tips
- Be sure to identify the type of parting edge you’re dealing with as each is handled differently. More on this later.
- When machining your rod(s), be sure to clamp them into the machine firmly. If they are at all loose, the grinding wheel may push the rod up so that you are removing less material than you planned.
- Always machine the full set of rods and caps the same.
- When finished grinding, clean bolt holes to remove any chips or debris that may have accumulated then install new bolts.
As stated before, most of the connecting rods you will deal with have a straight parting edge. You may also come across rods with Tongue & Groove (T&G), Serrated or Fractured parting edges. Due to the many irregular edges common in serrated and fractured parting edges, there isn’t much you can do to machine these.
Tongue & Groove (T&G) parting edges can be machined but there is a very specific way in which to work. First off, it’s essential to note that most manufacturers incorporate a slight clearance between the tongue and bottom of the groove. When grinding these rods, be sure the amount of material removed does not exceed the amount clearance or you will need to grind the tongue to restore proper clearance.
“To grind tongue, place parting edge of gauge rod so tongue surface DOES NOT rest in any of the grooves of the gauge rod and place a shim under the groove surface approximately equal to the thickness of the tongue. Clamp tightly, remove shim and grind as normal.” – page 301-302
The most common way to recondition connecting rod housing bores is through honing. Machines can be set up quickly and produce a round straight bore that is often equal to or better than the OE manufacturer’s. Interchangeable mandrels of various sizes reduce set-up time so you can produce more in less time. Connecting rod mandrels use a double-wide stone arrangement designed to increase the stone surface area to better alignment and faster material removal.
As with most honing operations, be sure to use enough honing oil. Always use a honing oil that is specifically formulated for this type of honing such as Goodson’s Rod Honing Oil (RHO-10 or RHO-50) or Sunnen’s Mineral Based Honing Oil (MAN-845). Also, keep your supply of honing oil clean by filtering it and changing it regularly. This will enhance its performance and improve your finished product.
Most rod honing is performed with a horizontal honing machine. These are available in manual, power-stroked or CNC options.
“Let’s examine some of the capabilities of manual horizontal honing machines. They can be used to size connecting rod housing and pin bores, small engines and motorcycle cylinder assemblies, and to fit steering king-pins, just to name a few. Any bored hole used for a bearing surface or alignment purposes can benefit greatly from honing. Closer tolerances can be maintained with greater ease and productivity.” – page 303
Common Bore Errors
There are ten common bore errors associated with machining, heat treating or holding the part. These include:
- out of round
- boring marks
- reamer chatter
Honing can correct all ten of these errors. Honing is characterized by “large areas of abrasive contact; low cutting pressure, low velocity, floating tool or part and automatic centering of the tool by expansion inside the bore.” – page 303.
Key considerations when Rod Honing:
Select the proper stone composition. There are generally four stone compositions from which to choose; roughing, general purpose, finishing and for steel. Both Goodson and Sunnen stones use the same numbering system. Roughing stones are 5s (for example: Sunnen’s KL-5 or Goodson’s HK-5), General Purpose stones are 7s, Finishing are 13s and Steel at 14s).
Select the correct housing unit. Honing mandrels are available in a wide range of bores. Depending on the part you’re honing, select the most suitable mandrel size. Follow the manufacturer’s directions for assembly and set-up.
One final thought
A final step when reconditioning connecting rods that is often overlooked is demagnetizing the parts before you start putting the engine back together. This is critical to prevent premature engine failure. Heat and friction from engine operation and the machining process can induce magnetism which must be removed. Check out this previous post on the importance of demagnetizing.
This has been a brief overview of connecting rod reconditioning. For more information, check out Engine Builder Magazine’s “Back to Basics: Reconditioning Connecting Rods” and “Connecting Rod Reconditioning: More To It Than You Might Think”. You can also read the entire section from the Sunnen Engine Rebuilding Handbook here.
As usual, if you have any additional questions about this topic, contact the Goodson Techxperts by email or phone at 1-800-533-8010.
Pistons should be inspected and measured at several locations including the skirt, top, middle and bottom ring lands and the pin bore.
The skirt should always be measured exactly 90º from the pin bore. The actual height location may vary from manufacturer to manufacturer, but most specify a location the same height as the pin bore location.
After inspecting the ring lands, check each with a new ring. It is important to use new rings for the measuring procedure because wear will reduce the width of the old rings. A feeler gauge is placed between the ring and the top of the land. Under no circumstances should the ring-to-land clearance exceed .006” (0.15mm). Worn out ring lands do not let the rings seal in the explosive pressures of the burning air-fuel charge. It is not advisable to reuse pistons during a rebuild and rings should never be reused.
The pin bore must be gauged with the AG-300 Precision Gauge. Bores should be round and straight, showing no signs of taper or out-of-round. Those exceeding .0005” (.013mm) should be fitted with oversize pins. The following procedure is used to measure the piston:
- Select an appropriate sized micrometer and measure the piston skirt 90º from the pin hole location, as per manufacturer specifications. Record this measurement. Remember that the piston skirts are cam-ground (see image above).
- Measure the skirt just below the bottom ring groove and then measure the lowest part of the skirt. Record both measurements. Use them to determine the amount of taper found on the skirt. The bottom part of the skirt will always be larger than the top.
- Install a new piston ring backwards into the top ring groove. Insert the largest thickness feeler gauge that fits between the ring and groove. If the thickness exceeds .006” (0.15mm), replace the piston.
- Measure the pin bore for size and out-of-round, as per manufacturer’s specifications. Any deviation over .0005” (.002mm) is unacceptable and may require the installation of an oversize pin.
Inspect your piston pins for damage. Complete failure (breakage) of the piston pin is a very rare occurrence in engines. Damage caused from incorrect fit or detonation, however, are commonplace. Improper installation of the pin can cause galling of the pin, rod and piston. If left uncorrected, the piston pin bore will quickly fail. Oversize pins can often be fitted to the piston and rod to salvage the assembly.
Detonation damage to the piston pin can also lead to early pin failure. Over-advanced ignition timing is the likely cause. Another common problem you’ll see is pin damage due to inadequate use of assembly lube.
Today’s connecting rods strain under 3,000+ HP in racing engines or as few as 50 to 300 HP in a passenger car. Regardless of the vehicle’s use, the connecting rod must be free of defects, straight and on-size. If the connecting rod is overlooked during an engine rebuild, the result is shortened engine life.
The tunnel or housing bore of the rod plays a significant role in engine operation. It must be round and parallel to the piston pin bore. Surface finish must be quite low in order to efficiently transfer heat away from the bearing inserts.
After many hours of operation the housing bore can become out-of-round. The majority of the out-of-round condition can be measured where the cap and rod mate (the parting edge). Measurements at the parting edge tend to be larger than when the rod is measured end-to-end. Out-of-round is what we call the condition when one measurement location is larger than another 90º away. A limited amount of out-of-round is acceptable.
Connecting Rod Measurement
The connecting rod must be measured for alignment. In addition, it must be measured at the rod journal bearing housing (tunnel) bore, the piston pin (tunnel) bore and the center-to-center distance. The bearing housing and pin bores are measured with a Sunnen AG-300 precision gauge or dial bore gauge for size and out-of-round. Center-to-center distance can be measured with a vernier caliper.
The center-to-center distance between the large and small ends of the connecting rod must be maintained within .005” (0.13mm); in most cars, less is better. Diesel engines often require a maximum variation of .002” (0.05mm). The large and small ends of the rod should be measured for out-of-round, taper and barrel, and should not exceed a variation of .0005” (0.002mm). Measurements are performed with the Sunnen AG-300 Precision Gauge or with a Dial Bore Gauge. A snap gauge or inside micrometer is NOT advised.
Here’s how to measure the connecting rod with the AG-300:
- Set your micrometer to the minimum or maximum housing bore diameter.
- Install the appropriate gauge points onto the gauge fingers (see chart). Adjust the AG-300 precision gauge indicator needle to zero and lock into place.
- Place the rod onto the measurement points near the parting edge (beam facing 12 o’clock or 6 o’clock position) so that the thrust surface of the rod lays flat against the face of the AG-300. Next, rotate the rod until you obtain a minimum reading (rod beam will be located at or around the 3 o’clock or 9 0’clock position on the indicator). Any deviation from the maximum bore means that the rod should be resized by honing or boring.
- Place a pair of the appropriate-diameter piston pins into the setting block and clamp into place. Adjust the AG-300 Precision Gauge (zero the indicator needle) and lock into place.
- Place the pin end of the connecting rod onto the measuring points and rotate until you obtain the maximum size. If the size exceeds the manufacturer’s specifications the rod will need to be reconditioned.
|AG-300 GAUGE POINT RANGE|
|Midget||.375” (9.53mm)||.750” (19.05mm)|
|Standard||.720” (18.29mm)||1.530” (38.86mm)|
|Medium||1.500” (38.10mm)||2.250” (57.15mm)|
|Large||1.940” (49.28mm)||2.690” (68.33mm)|
|X-Large||2.625” (66.68mm)||3.375” (85.73mm)|
One last warning; the area from 2 o’clock to 8 o’clock and 3 o’clock to 9 o’clock positions will experience the most out-of-round condition.
The rod is considered acceptable if the parting edge location does not entirely clean up during the reconditioning process. This small area allows a small pool of oil to form and provides increased oil wedge during lubrication. To promote this same effect, some bearing manufacturers make a “Delta-wall” bearing where the edges of the insert are thinned. By thinning the edges you promote the formation of an oil pool.
Connecting rods stretch slightly at the parting line during extreme operating conditions. The housing bore pulls in toward the journal, while the center-to-center length increases. Over long periods of time, the housing bore is forced out-of-round to a point that it never returns to a round shape.
Rods having “gone to metal” (housing bore making physical contact with the crankshaft) must be inspected very closely during non-destructive testing (NDT). Metal build-up on the housing bore interior should be removed with a file before reconditioning. It is imperative that these rods be resized before returning them to service. Should cracks or fractures be found during NDT, replace the rod without hesitation.
The press-fit piston pin retention system is used on most engines. It is important to measure the pin bore for size. Press-fit pin bores are made slightly smaller (approx. 0.0008” to 0.0012” or 0.02 to 0.03mm) than the diameter of the pin. CAUTION: Always measure the pin bore before the pin is installed. Excessive material in the pin bore will cause the pin to seize half-way through during installation and cause the pin to become loose. Oversize pins are available for most applications to correct loose fitting or out-of-specification pins. In the majority of cases, press-fit pin bores do not require reconditioning. If a press-fit pin must be resized for an oversize piston, so too will the piston pin bore.
On rods fitted with free-floating pins, bronze bushings are used to support the pin. There are two methods used for their repair: Fit an oversize pin to the rod and piston; or remove and replace and fit a new pin bushing for the same (stock) size pin.
The housing the pin bores must be perpendicular to one another. Misalignment can cause rubbing or the piston skirts on the cylinders and cause edge-loading on the bearing by the crankshaft. Both problems will result in early engine failure. Measurement of the rod for twist, bend and center-to-center distances are made with sophisticated rod alignment machines.
Goodson thanks Sunnen Products Company for permission to use this information from Sunnen’s Complete Cylinder Head and Engine Building Handbook.
By Chris Jensen, Goodson Techxpert
When I was asked to write this piece on Assembly Lubes, my first question, “How much space do you have?”
I’ve been in this business for over 30 years and a lot has changed. How would I boil all of that down to fit into a brief piece? So I did some online research to add to what I already knew. Wouldn’t you know it; there’s tons of information out there. In fact, when I Googled “engine assembly lubes” I got 4.5 million (yes, million!) results.
Rather than rehash everything that’s already been said about assembly lubes, I’m going to give you a brief rundown of the products Goodson carries and where to use each one.
But before I do that, let’s talk about the purpose of assembly lubes.
When you start assembling an engine you’re going to be putting metal against metal. To protect that metal, you need some kind of lube. That’s where assembly lubes come in. Assembly lubes are intended to protect the metal from overheating and reduce friction on initial start-up. Sounds easy, right? Wrong. Different surfaces need different types of lubrication and that brings us back to the products that Goodson carries.
Press Fit Lubes
These assembly lubes are used for exactly what the name implies – pressing parts together. They’re ideal for valve guides, piston pins, cylinder sleeves, etc. This light weight lube is available as a spray or in a can with a brush applicator. It’s applied to the parts you’re pressing together to avoid scoring, gouging and galling.
Spray Assembly Lube
Like the name says, this lube is also a spray. It is ideal for lubricating areas that are hard to reach with a traditional lube. Goodson recommends using Spray Assembly Lube on valve train components to eliminate critical run-in of new and rebuilt high performance parts.
Extreme Pressure Lube
One of the biggest problems that needed to be overcome with assembly lubes was the high pressure exerted in some parts of the engine. This pressure can cause lubes to break down, making them ineffective. That led to a whole group of lubes for extreme pressure (EP) including Goodson’s Extreme Pressure Lube. This product is a highly refined petroleum product in a grease form that contains no lead, graphite or minerals. Being a grease based product, Extreme Pressure Lube goes on thick and as the engine heats and oil circulates, the grease base breaks down and mixes with the oil. This is what you want to happen. You don’t want a grease base that is not oil soluble as the substrate will break down under heat and pressure and wind up in your oil filter or worse, plugging up an oil feed hole. Not good, if you know what I mean.
We recommend Extreme Pressure Lube for pushrod tips, rocker arms, valve stem tips, distributor drive gears and blower drive gears and most engine fasteners.
Cam-Shield® Camshaft Assembly Paste
This is our newest addition to the Goodson Assembly Lube assortment. Again, as the name implies, this assembly paste if for use with camshafts (especially flat-tappet camshafts) and lifters. It provides anti-wear protection during break-in. The most important component of Cam-Shield is ZDDP, or Zinc Dialkyl Dithiophosphate. Now you know why they call it ZDDP.
ZDDP is another extreme pressure additive which is essential to make up for the lack of zinc in most commercial motor oils today. This zinc helps the lube cling to the part in question until break-in has occurred.
We recommend Cam-Shield for racing, street, classic, ag, diesel and marine camshafts including mechanical and hydraulic camshafts and lifters.
Blood Friction Master® Engine Assembly Lube
First of all, this product has nothing to do with blood. It was created by the Alan C Blood Company, which is where the name originates.
Blood Friction Master contains a low friction additive (PTFE) for use in dry start-ups. The creamy formula forms a slick wall between moving parts to protect them during start-up pressure and will cling until it is dissolved by the circulating oil. If your assembled engine is going to sit for a while before start-up, this is the product to use as it has great long-term protection. Use Blood Friction Master on engine bearings.
First Lube Engine Assembly Lube
Last, but certainly not least, is the popular First Lube, a semi-synthetic assembly lube containing Zinc and Moly as well as other high pressure additives for maximum break-in protection. First Lube is compatible with all oils.
Use First Lube to pre-lube bearings, cams, lifters and valve trains. The tacky formula makes it easy to apply and the green color makes it easy to see where you’ve applied it.
As you can see, there are many Assembly Lube options available, and I’ve barely scratched the surface. If you’re interested in reading more about Assembly Lubes and Break-In Oils, check out Engine Builder Magazine’s website and search for Assembly Lubes. And as always, if you have any questions about this piece or any other technical question, contact the Goodson Techxperts at 1-800-533-8010 or email us.
By Dave Monyhan
Originally published in Engine Builder Magazine
Valve Spring: Almost all engines use valve springs to close the intake and exhaust valve during combustion cycles for internal or diesel combustion engines. Keep in mind the cam, pushrods, lifters, and rocker arms do all the work in opening these same valves, but it is the spring that closes and keeps that valve closed during the operation of the engine. These valve springs will be compressed and expanded over and over through their life cycle sometimes at more than 70,000 times in an hour for most high-performance engines, and over its life a valve spring could be compressed million, billions, or even trillion or more times during their life. Kind of like our current national dept. A valve spring also pushes back against all the other parts like the rocker arm, pushrod and lifter to maintain pressure on the cam lobe. Without valve springs, go fast engines, or any engine for that matter simply would not work. Well that statement may be argued by the fact that there is research going on as to having the valves completely eliminated and installing solenoids but we can discuss that in the future, so let’s stay on subject for now.
Valve Springs come in a (variety) cornucopia of sizes, configurations. Some are single springs with dampeners, others incorporate an inner spring and become a double spring, and then there is the extreme or the “Triple Spring.” Straight springs or beehive springs are also another choice.
Spring pressure is the key element to determine which spring should be used for what application. The camshaft design plays an all important role in determining which spring you need for that application. Lift is the critical spec or element when matching valve springs to the camshaft. The more lift you have the greater the pressure needs to be. The application of drag racing versus roundy-round or oval track racing also plays a role. Street car versus track only must be considered. I say that only because unlike a race car where we can and will change out valve spring at the end of every race, for a street application we want the long life so those springs must deliver the durability we need. Nobody wants to change out the valve springs on the Sunday Hot Rod every time we take the hot rod out for a ride. The quality of the valve spring you choose is also very important, broken valve springs are a nightmare for engine builders, because when the spring breaks, the valve drops, it hits the piston, and KA-BLUEY………….our oil pan is now a device for holding all the little fragments that just disintegrated themselves by that valve spring failing, and our race day is over, or our Sunday ride is now…….sitting by the side of the road waiting for the tow truck.
Springs not only come in different lengths and pressures they also come in different diameters. Generally speaking when you increase the spring pressure you will also increase the diameter of the valve spring itself. Now the cylinder head may not be machined for this increase in diameter so you will need to machine the spring seat to accommodate the larger spring. Fixed tooling is available to machine the spring seat, or you can also get an adjustable spring seat cutter to perform this operation right on your seat and guide machine.
Certain procedures are required for all applications of all valve springs, regardless of what you choose for your particular application. All valves springs need to be measured for specific opened and closed heights. All valve spring need to be confirmed that the pressure is what the manufacture says it is. And all High performance valve springs should be pre-cycled prior to being installed on the cylinder head.
I read a really cool article about “spring cycling” a method in which you “cycle” the valve springs to full coil bind several times so as to “break in” these high performance springs prior to final pressure testing, and measuring before installing them into the cylinder head. The claimed that they were able to measure almost 10 pounds of lost spring seat pressure by following this spring cycling procedure resulting in more accurate installed heights, that will result in less pressure loss when the engine is ran at its racing RPM range.
This cycling process is only for brand new high-performance springs and is not needed for the plain old stock or grocery getter type of applications. I also spoke to Joe Mondello and he stated that he cycles all of his race springs and then he also takes it one step further, by submitting them to a cycle of stress relieving, followed by a cycle of cryogenics freezing. You can learn more about Joe’s procedure here.
Measure, measure, measure!
Free length: this measurement is the first one you need to make. Free length is measured by placing the springs in a row, separating intake from exhaust if they are different (if they are rotator caps then they will be of different lengths) and measuring the overall length with no pressure being applied. If the variation is more than .025” the spring should be tossed. Next inspect your spring closely to ensure the top and bottom are parallel and that they are square. Also line them all in a row to check overall height with a straight edge. You can use a square to ensure the spring is straight by placing the spring on a flat surface and placing the square vertically next to the spring. Make sure the spring is square top to bottom and straight to with-in .062”.
Installed Height: This closed pressure is critical due to the fact that the spring must close and seal against vacuum and pressure. Weak spring pressures can allow the valve to bounce off the valve seat and this will cause a loss of power and excessive seat and valve wear. Closed valve spring pressure should be within 5 to 10 pounds of each other to be serviceable or approximately 10% from weakest to strongest measurement.
Open Valve Spring: This pressure must be enough to keep the lifter in contact with the camshaft during high RPMs. The valve must also maintain contact with the rocker arm and the rocker arm to the pushrod and the pushrod to the lifter and the lifter to the camshaft; if any of these clearances increase you will have engine failure.
Shims, VSIs, or Spring Washers are all the same thing with different names. These shims are used on mostly stock applications to increase the pressures, and are available in .015″, .030″ and .060″ thicknesses. They come in regular steel and hardened steel for high-performance applications. They allow you to fine tune the closed and open valve spring pressures to achieve correct installed height. If you find the need to shim past .060″………….replace that stock valve spring.
After you have laid out the springs and checked the free length, find the spec sheet you received with your new valve springs, or look up the spec in the manuals if you are re-using valve springs.
As with any component, you need to write everything down on the work order. Open height, Installed height, pressures at both settings and overall length. This way you have a paper trail to reference when it comes time to freshen up a race motor or in the event of failure. Probably the most important factor in selecting a valve spring is: Correct seat pressure, open pressure, and spring rate for the camshaft you are using.
Analog versus Digital
Now we all have a spring tester or tester in our shop right? Of course you do. But which type of tester do you have? Some models come only as a analog style of measuring pressure and height, and others in recent times have evolved to digital readouts for pressure down to the 1/10th of a pound, height can now be measured in .001″ (thousandths of an inch), choosing which spring tester is your first challenge to determine which type is best for you and your customers. I will start with the unit we all grew up with….the analog style of spring tester.
These units have been the backbone of the engine building trade for many years. They are fast, pretty accurate, and very easy to use. They are subject to the eye of the beholder. You have to insure you are looking correctly at the dial on the face to make sure pressure is read correctly and you have to look correctly at the measuring scale to insure your height is right. These units have an option to upgrade the measuring height to either a dial indicator or a digital readout. I highly recommend the digital readout to measure specific height. No options to upgrade the analog pressure dial, so calibration is very critical to insure your pressure is correct.
Whichever machine you have is the one you are going to use, so I am not here to tell you which to buy or say one is better than the other, but if you are shopping or in the mood to upgrade to a new machine, then I say check them all out. Contact your favorite shop supply company and compare the features and benefits. Find out what is, what isn’t, and who is going to be there for re-calibration, technical support before you buy, then select the machine that is best suited for you and your customers needs.
See ya in the shop!
Okay, you’ve already cut or ground your valve seats to the correct angles; you’ve ground the valve face in your valve refacer. Are you ready for final assembly of the cylinder head? Maybe, maybe not. The next step in many cases is to lap the valve to the valve seat for a final, perfect fit.
Lapping has been around for as long as engine building has been around. It’s a very simple, straightforward procedure.
All lapping tools work in the same manner. This means the tool is attached to the valve head, lapping compound is applied to the valve seat or the valve face and the tool is rotated left and right to lap the valve to the seat. It’s kind of like trying to start a campfire by spinning a stick fast enough to create enough heat to ignite your kindling. Of course, with valve lapping you’re not going to even try to start a fire, but the motion is the similar.
First, select the type of lapping tool you prefer. Goodson offers a variety of types and sizes including:
- Traditional Valve Lapping Sticks
- An Extra-Large Hand Valve Lapping Stick
- Vacuum Style Lapping Sticks
- Mechanical Valve Lapping Tool
- Powered Valve Lapping Tool
- Air Powered Valve Lapping Tool
Let’s take a look at each of them.
The traditional and extra-large lapping sticks are operated entirely by hand. They include a suction cup on one or both ends that you’ll use to attach it to the valve head. Sometimes a little spit will help to keep the suction cup attached. Of course, it’s always best to make sure all oils have been removed from the valve surface to ensure the suction cup mates to the valve. Suction cups are available in a variety of sizes to fit a range of valve heads.
Another type of valve lapping tool incorporates a pump to create vacuum to ensure the tool stays attached to the valve head. Don’t play with these unless you want to give yourself one heck of a hickie. They generate a lot of vacuum!
Next up is our Mechanical Valve Lapping Tool. Think fishing pole or egg beater. You crank the handle which creates the necessary oscillation.
If you’re looking for a powered lapping tool, you’re in luck. Goodson offers two of them. First is the Powered Lapping Tool that you drive with a power drill. The tool is designed to change the rotary action into an effective oscillating motion.
Last, but not least is the top shelf unit that most NHRA Top Fuel teams (and other race teams) use. The Air Powered Valve Lapping Tool. This heavy duty unit operates on 90 PSI of shop air and makes quick work of valve lapping.
The only thing left to talk about is Lapping Compound – a silicon-carbide, grease-based paste. Selecting the correct lapping compound is generally a matter of personal taste. Goodson offers several grits; from 120 to 1200 so you have lots to choose from. If you’re just getting started, you may want to experiment with different grits until you find what works best for you.
There are pros and cons to valve lapping and over time, you’ll find out which applications need to be lapped and which ones don’t. Practice makes perfect, but keep one thing in mind:
Lapping is a finishing step and should NOT be used to correct a bad seat, or worse yet, a valve that is imporoperly ground.
As always, if you have any questions about Valve Lapping or any other engine building topic, contact the Goodson Tech Services Department at 1-800-533-8010.
We’ve talked about how to find cracks in cylinder heads and blocks using magnetic particle inspection, dye penetrant inspection, vacuum testing and pressure testing. Now it’s time to discuss repairing the cracks you’ve found.
Let’s start by saying that not every crack you find needs to be repaired. If the crack isn’t located in an oil passage, bolt hole or other seal surface you don’t need to fix it completely. You do, however, need to stop the crack from growing. If you don’t, odds are you’ll be fixing it in the future. To stop the crack from growing you need to do what’s called “stop drilling”. This means you drill a tiny hole – about 1/8” diameter – just past the ends of the crack. This hole will relieve the stresses placed on the metal and keep the crack from expanding.
As with most operations in the machine shop, there are multiple methods you can use. Some methods work better on certain materials (cast iron v. aluminum, for example) and some are just pure personal preference. The most common methods for crack repair used in automotive shops are:
- Tapping & Plugging
- Inserting Sleeves
The focus of this post will be Crack Repair Plugs. We’ll talk about Welding, Sealants and Sleeves in the future.
Tapping & Plugging – the tried and true method of Crack Repair
The most common system available for tapping and plugging cracks is Irontite. As the name implies, this method of crack repair requires taps and plugs. You will also need correctly sized drills and tapered reamers. A special thanks to Irontite for providing the working photos in this post.
The first type of application we’ll talk about is installing tapered plugs to repair a crack in the area of a casting that is subject to high pressure and/or temperatures. A perfect example of this is a crack in the valve seat area of the head. To repair this type of crack you’ll install the plugs at an angle to the casting surface, not perpendicular. You will also be overlapping the plugs.
- Drill a plug hole at least 1/8” past the visible ends of the crack. This is to stop the crack from growing as you put pressure on the casting by installing plugs. Be sure to use compressed air to clean out the holes, every step of the way.
- After drilling, use a tapered reamer in the hole to make tapping easier and reduce tap breakage. This is particularly important where the material you’re drilling through is thick.
- Next tap the hole at one end of the crack. Be careful not to tap too deeply. You may run into another wall within the casting or the plug might seat too deeply before it is tight. One rule of thumb is to count the number of threads in the hole and tap so that the plug goes in the same number turns. For example, you have six threads so you turn the plug six times.
- Dip the end of the threaded plug with sealer such as Ceramic Motor Seal (CRS-16) or Fluid Weld (FW-2) and tighten it into the tapped hole.
- Saw off the excess plug material. For best results, be sure to cut at least half-way through the plug before snapping off the remaining material. This should keep the plugs from snapping off below the surface.
- Peen the surface of the plug and the surrounding area.
- Be sure to locate the next plug so that it overlaps the one you just installed. You will continue in this fashion until the entire crack has been repaired.
The peening process is extremely important. It helps close the threads at the surface of the casting. When peening, always peen away from the center of the plug. In the peening process, the position control of the air hammer is most important. It provides the necessary control over the direction of the ends of the peening tools.
A similar, but slightly different application is used when repairing cracks in easily accessible areas of the casting that aren’t subject to high pressure or temperature and the metal is relatively thin.
After the crack is outlined, drill and tap holes along the line of the crack about 1/4” to 1/2” apart. NOTE: Where the material is less than 1/4” thick, it is not necessary to ream before tapping.
- Capture the crack at each end.
- Torque the plugs in concurrently so that none of them will be loosened as other plugs are torqued in. Be sure to dip each of the plugs into sealer such as Ceramic Motor Seal (CRS-16) or Fluid Weld (FW-2).
- Cut the plugs off about 1/16” above the surface and peen them. Always peen from the center of the plug toward the thread in the plug.
- Peen the crack itself, peening inwardly toward the center of the crack.
You can also drill and tap the holes in a lacing fashion on opposite sides of the crack. You’ll torque the plugs in at the same time and then cut them off. Peen the plugs and the crack in the same manner as above. This process, in addition to closing the crack with additional metal and with peening the crack, develops a resistant elasticity in the metal which helps keep the crack closed.
THE IMPORTANCE OF PEENING IN CRACK REPAIR CANNOT BE OVEREMPHASIZED.
Some final tips, tricks and cautions.
Even when the hole is reamed with a tapered reamer be sure to use the proper amount of downward pressure with the tapered tap. You’ll also want to use a good tapping fluid such as TAP-O which doesn’t contain carbon tetrachloride.
A note from Irontite: “Irontite tapered plugs and tapered taps are designed so there will be a tight thread-to-thread fit when the plugs are torqued into position. When torquing in the plug, as an added assurance of a leak-proof fit, dip the plug in Irontite’s Ceramic Seal or Fluid Weld just before torquing it in. This will help close any porosity that may be present in the threaded hole of the casting. Ceramic Seal is recommended because, being fluid it will spread evenly on the threaded plug as it is torqued in.”
A couple of other tips that you need to know include using the same material for the plugs as the head is made of. For example, if you’re repairing a cast iron head, you’ll use iron plugs. You’ll also need to be sure that you have actually repaired the entire crack by pressure or vacuum testing.
As we said earlier, this is just one of the methods you can use to repair cracks in your cylinder heads and blocks. We’ll discuss the other methods in future posts. Be sure to check back often.
As always, if you have any additional questions about crack repair, be sure to contact the Goodson Tech Department at 1-800-533-8010 or email.
* This post is provided as an information resource only. This document should not be taken as a warranty for which Goodson or its vendors assume legal responsibility.
We’ve talked a lot about crack detection in our Tech Tips – everything from Wet and Dry Magnetic Particle Inspection to Dye Penetrant Crack Detection to Vacuum Testing. Here, we’re talking about pressure testing. This method is often used along with one of those listed above as a final check that all of the cracks or pinholes have been repaired. Of course, just like life, it can’t be totally simple; there are two ways to perform pressure testing – wet or dry. The good news is the procedures are essentially the same regardless of which method you choose.
First of all, the head being tested needs to be completely clean. You will attach a special block-off plate to the head to seal off the water passages, then pump pressurized air into the head through an air line inserted into a water port. Some sources will tell you to use about 60 psi, but in my experience, 20 to 25 psi is adequate. Some heads have core plugs pressed into them and these will blow out at 60 psi. It’s not only an inconvenience, it’s a safety hazard.
Here’s where the methods differ. With the wet method, you’ll lower the head into a water tank until it’s completely submerged. If you have holes or cracks, the escaping air bubbles will show you where. The dry method is similar. Instead of taking the head to the water, you’re bringing the water to the head. Once the head is pressurized, you’ll spray it with a soapy solution (bubble fluid or a little dish soap in water). If there are cracks or holes, the solution will bubble up and you’ll know where you need to repair.
Pressure testing is one of the easiest of the crack detection methods available. But a major drawback is that pressure testing can’t identify all cracks. Surface cracks that don’t connect to a water passage won’t show any leakage so you could miss those if you just use pressure testing.