Valve Grinder Chuck Inspection
Chuck accuracy is critical to producing a quality valve job.
Most O.E.M.'s require a valve face run-out to be below .0015. To accomplish this, the chuck in a valve grinder must not only run-out below .0015, but must repeat this every time.
High performance engines require even greater accuracy. In some cases run-out must be below .0005.
Start by finding a known round and straight part. A valve seat pilot, carbide if you have one will work very well. If you do not have one, use a section of drill rod that is straight and round. This will be your test piece.
- Insert the test piece into the chuck so that it is gripped correctly and has at least two inches of protrusion past the face of the chuck.
- Install a dial indicator (.0000 reading if possible) so as to have the plunger contact the test piece one inch from the face of the chuck.
- Turn the machine on and observe the indicator as the chuck is rotating. The reading at this point should not exceed .0015.
If the reading is inexcess of the .0015, you can first disassemble the chuck and clean it thoroughly. (Follow directions given in the machine manual). Examine the ramps on which the ball bearings ride, if wear is evident (grooves), the chuck will require placement. Kwik-Way provides new chucks that have less than .0005 run out and for the standard SVSIID and a Hi-Performance version with less than .0002 run out.
If you have any quesitons in regards to chuck performance, or if you need a replacement chuck, contact;
Kwik-Way Tech Services at 800-553-5953.
What is special about the carbide?
- Our carbide is a special formulation of carbide and additives designed for high speed, high feed machine applicaitons.
- Our carbide is also coated to improve edge wear and heat resistance providing longer tool life.
- The radius is larger than on standard brake carbide and provides for smoother surface finishes.
- We use a positive tool rake, which increases the ability to remove stock at higher feed rates while maintaining excellent surface finishes.
In closing, you can use the 104 carbide technology (insert) on the Model 102 and realize improved surface finishes, and increased tool life.
The 109-1092-32 uses a .032 radii. This means that the -32 has the potential to provide a smoother surface finish. (Standard inserts normally use a .016 in radii)
Positive rake tools can not be turned over, but they can be switched from side to side, which can potentially double the life (number of rotor surfaces) of the tool.
When a brake rotor deviates from its axial plane viewed from the front edge of the rotor, this refers to a "wobble" of the rotor as it rotates. This off-center deviation is called warp, axial runout or lateral runout, all referring to the same problem that results in annoying brake pedal pulsation, often accompanied by steering wheel wobble/vibration during braking.
Rotor runout may or may not be caused by rotor thickness variation. If a rotor thickness check shows no evidence of a variable dimension, the rotor may be rotating off its true axis as a result of other damage. The wheel bearing may be badly worn and excessively loose, which would cause erratic rotor wobble as the vehicle rolls down the road. In the case of a hubless rotor (where a thin-hat rotor mounts onto a spindle-mounted hub flange), check the contact area between the hub and rotor hat. A large burr or contamination (caused by rust or grit buildup) may create an uneven mounting surface that will cause the rotor to rotate off its intended axis.
Another potential cause (one that is common where today's thin-hat rotors are used) is poor wheel installation practice. If, during wheel installation, the wheel fasteners were improperly tightened, it's very likely that the rotor hat may have warped due to uneven or excessive fastener torque. If you suspect this to be the case, a quick check involves loosening all wheel fasteners and retorquing in the correct pattern and at the correct torque values (do this one wheel at a time to keep track of any potential improvement). After the wheel has been properly retorqued, perform a road test to check for pedal pulsation. If the problem has lessened somewhat (or if you're lucky, maybe it's disappeared), you know you're on the right track. If pulsation has lessened but is still present, and you've ruled out bearing and flange-to-hat mating, chances are good that a light cleanup of the rotor on a lathe will provide the final fix. If not, you may be forced to simply replace the rotor.
MEASURING ROTOR THICKNESS
Before measuring for lateral runout, perform a rotor thickness check. This will determine whether or not that rotor is indeed serviceable. Also, you may find gross thickness variations that will readily explain the pedal pulsation problem.
Check the rotor thickness at eight equidistant points around the perimeter of the rotor (divide the rotor into seven pie slices). Never base your determination for rotor warpage by measuring only one spot on the rotor. Variation in rotor thickness will always cause pedal pulsation. That variation might be the result of excess heat buildup that has warped the rotor, or the rotor may be contaminated by isolated thick spots caused by rust or corrosion buildup (prevalent in vehicles that may have been stored for extended periods of time, where the contact area between pad and rotor may have created rust deposits). Use a micrometer to measure rotor thickness, preferably a specialty mic that's designed specifically for measuring rotors. The unit pictured in this article is a Central Tools #6459 digital disc brake gauge, which features one flat anvil and one pointed anvil. The pointed anvil feature allows measurement of the real minimum thickness of a scored rotor, as compared to a mic that has two flat anvils. The flat anvil surfaces will only contact the top, or high spot of any grooves or scoring lines.
A dial indicator must be used to check lateral runout. The dial indicator must be securely mounted to a stationary (and adjustable) fixture. For on-the-car measuring, attach the fixture to a stationary location such as the spindle or control arm. Locate the dial indicator's plunge tip about an inch inboard of the rotor edge, and zero the indicator. Rotate the rotor manually through a 360-degree rotation, watching the dial indicator for changes in runout. The unit shown in this article is a Central Tools #6450 rotor and ball joint gauge. This features an easy-to-use clamp mount and flexible adjustment arm that solidly locks into a steady position.
Specifications may vary among makes and models, but you can probably use .002" to .005" as your maximum runout limit. In the case of a hubless rotor, if excessive runout is found, index mark the rotor to the hub by placing a chalk mark at a stud and at the adjacent area on the rotor hat. Then relocate the rotor clockwise to the next stud position, and perform your runout measurement again. In this way, you're attempting to "match" the rotor to the hub. Due to potential minor deviations on the machined surfaces of both the rotor hat underside and the hub flange, repositioning the rotor may create an "optimum location" that minimizes total assembled runout.
If you want to check runout of the rotor independently of the hub, chuck the rotor on your lathe and perform a dial indicator reading. It's also a good idea, in an effort to remove other variables from the equation, to make a runout reading of the hub flange itself, with rotor removed. If the flange itself is causing the runout problem, you'll be able to isolate the cause.
WHEEL TIGHTENING PRECAUTIONS
To prevent fastener-tightening-related rotor warpage, make sure the studs are in serviceable condition (check for thread integrity and repair/replace studs as needed), and check the condition of the nuts' threads as well. Never use fasteners that are suspect. Also make sure all threaded locations are clean and free of dirt, grit or other contaminants (poor quality or unclean threads can easily result in incorrect torque values). And NEVER use an impact gun with a standard impact socket to tighten wheel nuts. I don't care what someone else tells you with regard to this. The only proper method of wheel installation, especially when dealing with alloy wheels and thin-hat rotors, is to hand-tighten all wheel fasteners.
The only possible exception is the use of a "Torqstik." This is a torsion-bar type anvil socket that is designed to relieve tightening force as the predetermined torque is reached. If you want to follow this approach, you'll need a torque stick for each size nut and torque range (they are available, color-coded for easy identification, in 17mm @ 55 ft lbs; 17mm @ 80 ft lbs; 19mm @ 65 ft lbs; 19mm @ 80 ft lbs; 19mm @ 100 ft lbs; 13/16"@ 100 ft lbs; 21mm @ 60 ft lbs; 21mm @ 80 ft lbs; 22mm @ 120 ft lbs; 22mm @ 140 ft lbs; and 22mm @ 170 ft lbs. Heavier ratings are available in 1" drive for super-heavy-duty applications as well). These Torqsticks are available from many sources. If you're determined to use an impact gun to tighten wheel fasteners, this is the only sensible approach. Always follow the proper tightening sequence:
• For five bolt wheels, start at 12 o'clock, then the 5 o'clock, then 10 o'clock, then 2 o'clock and finally 7 o'clock.
• For a six bolt wheel, start at 12 o'clock, then 6 o'clock, then 2 o'clock, then 7 o'clock, then 5 o'clock and finally 10 o'clock.
This criss-cross routing enables you to evenly distribute the clamping force across the face of the wheel and rotor hub. Using a random tightening pattern and guesswork clamping forces is a sure way to create a rotor warpage, ruining an otherwise perfect job.
- On vehicles with hubless rotors, brake vibration and pedal pulsation may be caused by any of the following...
- Improperly torqued wheel fasteners (torque uneven, too high, or not tightened in proper sequence)
- Contamination (rust, dirt, crud) between hub and rotor hat
- Damaged hub (check runout of rotor on lathe)
- Extreme heat buildup/isolated hot spots
- Worn/damaged wheel bearing
- Excess rust/corrosion buildup in isolated spots on rotor
Recurring lateral runout can be a nagging problem. The customer may have complained of a pulsating pedal, and shortly after your shop resurfaced the rotor, the vehicle returns with the same complaint. Causes can include a number of possibilities. First perform a rotational torque test on each front wheel. Do this by applying and releasing the brake pedal 6-12 times.
Then rotate the wheel using a beam-type torque wrench on a lug nut, noting the amount of rotational drag indicated on the torque wrench. Next, open the caliper's bleed valve to relieve fluid pressure and re-test for rotational drag.
IF ROTATIONAL DRAG WAS REDUCED AFTER OPENING THE BLEEDER, check for pedal bind. Try to pull up on the pedal. If it moved, re-test the wheel for rotational drag. If drag was reduced, adjust or repair the pedal linkage, brake light switch or cruise control switch as necessary. If this wasn't the problem, check the vacuum booster by pumping the pedal with ignition off. If rotational drag was reduced after eliminating vacuum from the booster, the atmospheric valve is likely sticking, so replace the booster. Note: pull with about 40-60 ft lbs force. However, if the vehicle has ABS, pull the pedal gently, as the rod may be pulled out of its socket.
If the problem is still undiscovered, loosen the master cylinder and pull it away from the booster by 1/4"-1 /2" (don't loosen fluid lines). If this reduced rotational drag, the master cylinder piston is not fully returning. Repair the pedal pivot shaft/linkage, or replace the offending master cylinder, booster or pushrod. Note : on some compact cars, the pedal shaft or the firewall may have been distorted, preventing full pedal return. Check this as a possibility
If the drag was not reduced when the master was pulled away from the booster, check for fluid contamination. This may be indicated by a swollen or slimy rubber diaphragm in the master cylinder. If that's the case, rebuild or replace the master cylinder, and all hydraulic components (calipers, hoses, wheel cylinders) and flush the entire system and replace the brake fluid.
If no contamination is present, trace the fluid lines. Begin by opening the fluid line at the master cylinder. If rotational drag is reduced, replace the master cylinder. If drag was unaffected, open the fluid line below
the combination valve. If drag is reduced, replace the combination valve. If not, open the connection where the steel line meets the flexible hose. If drag is reduced, replace that steel line. If drag isn't reduced, replace the hose.
IF ROTATIONAL DRAG WAS NOT REDUCED AFTER OPENING THE BLEEDER, strike the caliper twice with a rubber mallet to relieve any potential mechanical binding at the piston or at the caliper slides.
If rotational drag was reduced after striking the caliper, rebuild or replace the caliper as needed, and clean and lube the slides. In the case of a twin-piston caliper, make sure both sides have the same type piston (steel/steel, etc.) Also make sure the sliding pins are of the latest style, and use only silicone grease for slide/pin lubrication.
If drag still has not been reduced, check the rear brake function (road test). Accelerate to 20 mph, and carefully apply the parking brake (vehicle must be travelling straight, and you must hold the release button down during this to avoid loss of vehicle control! Perform this test in your parking lot or in a nearby large parking lot if possible). Service the rear brakes as needed to obtain full stopping ability. Adjust the height-sensing proportioning valve linkage if necessary.
Check the wear pattern on the brake pedal. If excess left side wear is indicated, the driver has likely been riding the brakes with his/her left foot, and dragging the pads as a result (increasing heat buildup). If excess right side wear is shown on the pedal, excess brake wear/heat buildup may be the result of towing or other heavy-duty use.
When a rotor warps, even though remachining may regain disc "flatness," the rotor may retain an internal stress "memory" will cause the rotor to eventually warp again. Aside from using a stress relieving process (such as cryogenics or vibrational stress relief, processes that are used in some racing applications to stabilize metals), the only answer is to replace the rotor, if recurring "warpage" continues.
A very common concern with any boring bar is that the bar sometimes will not repeat on bored size. This can be caused by one a few different things, or a combination of more than one.
You set your mike and bore a hole and find the hole is oversized, you reset the mike and the next hole is then undersized, obviously there is something that is not right.
First thing we would look for are scores or scratches in the micometer face. If the mike is damaged, the bar will not repeat.The mike should be returned to KW and the face reground and repaired.
Micrometer stem bend, will cause the same problems depending on the amount of bend and the amount of stock to be removed. A quick way to determine if the stem is bent is to insert a feeler gauge (.002) between the face of the mike and the tool bit, then tighten the bit. The feeler gauge should stay in place, and if you slowy rotate the mike in the boring head, the tension in the feeler gauge should not increse or decrease. If it does, the stem is bent and requires replacement.
Another thing to check is if the micrometer not locating into the boring head correctly. The stem of the mike has a V-groove in it which works with a spring loaded ball bearing to insure correct position of the mike into the head every time. If the groove is worn or the ball is out of adjustment, the bar will not repeat on size. The micrometer should "snap" into the head and when slight rearward pressure is applied, the mike should snap back into the boring head. If it does not the ball positon will need to be adjusted. Contact Tech Services for assistance in this case.
If you tighten the tool bit and the tool bit moves away from the feeler gauge, and the feeler becomes loose, there is a different problem. Either the tool gib, tool holder or boring head is worn. You can examine the tool holder quite easily by simply checking the angle where the gib plate contacts the tool holder for visable wear and also feel it for any step. If worn, it will require replacement. You will need to remove the gib from the boring head to examine it for wear also, if the tool holder is worn, it is likely the gib will be worn also.
The boring head can also be worn, and cause the same problem as the tool gib or holder. If the boring head is worn, then the head will need to be replaced. Rebuilding a boring head is only something that the factory can do, and all heads may not be repairable. A combination of two or more of these concerns may be found on the same machine. These findings are normally on very old or high service units.
These are but a few possible causes for potential boring errors in bore size.
As always please contact KW Tech services for further help if required.
For the past three or four decades the automotive industry witnessed substantial reductions in the number of valve servicing operations being performed. Leaded, high octane fuel burned in high compression engines developing high horsepower was the reason.
Even when these engines did need valve service the car owner might not be aware of it because his car's engine had a great excess of power which he hardly ever called upon.
Today the picture is changing. Lower compression ratios and unleaded fuels are the order of the day. They are the result of the need to reduce air pollution. And with these new conditions comes the need for maintaining high engine efficiency if performance and emission control standards are to be maintained
Valve misalignment can occur in a comparatively new engine of any make. How many car operators know or understand this? The service shop operator must begin to develop new means and methods for selling service, and especially for selling car owners on the importance of servicing valve and valve seats. He can easily do this by explaining the benefits that will be effected from a valve realigning operation.
Above is a new valve, true and mechanically accurate in all its proportions — the condition in which it is installed in an engine. The valve face and the valve stem are concentric with the same center line — the center line of the valve stem itself.
Above is a warped valve. The warp- age occurs only in that part which is subjected to extreme heat — the portion above the guide — and in the valve head. The valve face must be restored to concentricity with the portion of the stem that operates in the guide.
ENGINE BLOCKS CHANGE SHAPE DURING SEASONING PERIOD — USUALLY WITHIN THE FIRST FIVE THOUSAND MILES
Years ago it was customary for engine manufacturers to stack engine blocks out in the weather so that they might become seasoned. These were corded up like wood. Tracks were laid between the piles and workmen were kept constantly busy bringing in the blocks and facing off first the top and then the bottom; then placing them out in the weather again for another period of seasoning between machine operations. All of this was done to eliminate casting strain. This seasoning operation as a rule took from six months to a year after the casting was made.
Compare this with our present day method of pouring iron ore into an electric furnace and having it come out of the plant in from forty-eight to sixty hours — a complete running engine. These blocks are normalized or heat-treated to eliminate casting strains. But remember! When these blocks are heated and cooled over a period of time in the operation of an engine, or when the head nuts or bolts are not drawn down evenly with a torque wrench, the different shapes and radii of the manifold near the valve guide will cause misalignment of the guide to the seat, and must be corrected in order to get maximum performance from the engine.
HARDENED VALVE SEATS PREVENT VALVES FROM HAMMERING IN
Since the introduction of hardened valve seats it is impossible for the valve to hammer in as before. Therefore, the misalignment caused by warping of or changing of the shape of the metal in the block will set up a friction between the valve stem and the valve guide. This will soon wear the valve guide as well as the valve stem and to a point that will partially destroy the effectiveness of the valves. A normally worn valve guide is illustrated above. It is worn at points A-B at top left hand and at bottom right hand for the reason that the valve seat is higher at the right hand side. The valve strikes the high side of the seat first, then bounces to the left. As the valve spring pulls the valve down, valve stem friction causes the wear as shown.
BLOCK IS DISTORTED IF HEAD NUTS ARE TIGHTENED WITHOUT USE OF TORQUE WRENCH
Another factor entering into valve misalignment is the distorting strain set up in the block or head due to the unevenness of tightening which results when a torque wrench is not used. Due to differences in stance of the operator, and other human factors, some of the head nuts or bolts are tightened excessively if torque is not measured. This always happens when a torque wrench is not used. In tightening head nuts or bolts, follow factory torque recommendations.
If you will check the valve seat nearest the bolts that are tightened excessively you will find the part of the seat nearest the bolt will be worn shiny; while the side of the seat opposite to or away from the bolt will be pitted or burned. It therefore follows that a properly aligned valve job may easily be spoiled by improper tightening of cylinder head nuts or bolts.
A properly aligned valve job may easily be spoiled by improper tightening of cylinder head nuts or bolts. The remedy is simple. It is as easy to use a torque wrench as any socket handle.
LOCATING FOR REALIGNING VALVE SEATS
Several mei.iods are being used today to locate the grinder for realigning and resurfacing valve seats. There is, however, one accepted method that engineering practice has never improved upon. As an illustration, it has been common practice in machine shops for the past thirty or forty years to use what is known as a "machine arbor." This is a piece of hardened and ground steel microscopically tapered from end to end. Whenever a piece of precision work having a hole in the center was brought back to a lathe for machining, such an arbor was used to keep the machine work concentric with the hole in the center of the piece.
The Kwik-Way Manufacturing Company recognized the infallible accuracy of this procedure and designed a Tapered Arbor to be used for centering the valve seat alignment operation. The application of this arbor to the operation of servicing valve seats is covered by patents owned by the Kwik-Way Manufacturing Company and although widely imitated, it is not or should not be made available for this use by other manufacturers.
NONE BUT A TAPERED ARBOR WILL PROPERLY ALIGN A VALVE SEAT RECONDITIONING OPERATION
The Kwik-Way Tapered Arbor, commonly known as a Pilot, is microscopically tapered throughout the stem (the part that enters the guide). When inserted in the guide it takes its alignment from the least worn portion of the guide, which is towards the center, and not from the bell mouth portions on either end. Note (illustration at right) that the arbor does not contact the worn portions A-B at top and bottom of the guide and is not misaligned by those worn portions. It is accurately aligned by the unworn part. The Kwik-Way Eccentrimeter (below) measures the concentricity of the valve seat with relation to the guide. Some of the imitations have a straight surface for the greater portion of the stem with a conical or cork- shaped part for about an inch at the top. Since the valve has been crowded over to one side of the valve guide due to misalignment and the peculiarities of valve spring tension, the wear caused by this crowding of the valve stem to one side makes the top portion of the guide a most unsatisfactory point from which to locate for reconditioning of the seat. The seat cannot be reconditioned and realigned so it will be concentric with the actual center line of the valve guide.
CHECKING FOR WEAR IN VALVE GUIDE
In reconditioning a valve seat in an engine that has had considerable use, it is first necessary to determine whether or not the wear in the guide is beyond the point where the guide will be satisfactory for further use.
Through the use of the Kwik-Way Tapered Arbor the amount of wear can be determined. Kwik-Way Tapered Arbors are manufactured in steps of one-thousandth of an inch in undersize and oversize. By using a range of arbors, the amount of guide wear may easily be determined. The arbor, when inserted in the guide, actually becomes a plug gage for the worn guide. It is not good practice to use guides that are worn more than .003".
Insert another type arbor in a valve guide where there is considerable wear at the top and bottom. Try such an arbor as mentioned in preceding paragraphs and there will be an excessive misalignment due to the wedging of the cork or conical-shaped part of the arbor into the worn portion of the guide. Note (illustration left) that the conical or cork-shaped upper portion of that type arbor or pilot will contact the upper worn portion of the guide which also causes the lower portion to contact the bottom worn section of the guide. It is, therefore, misaligned by these worn portions. By checking such an arbor with an indicator, it is easy to prove this point as it is almost impossible to get the same reading twice. The Kwik-Way Tapered Arbor may be reinserted any number of times and checked with an indicator, and it will be proven that it will properly align itself each time it is inserted. It will be found that a seat trued up from a Kwik-Way Tapered Arbor is concentric with the actual center line of the valve stem guide.
ENGINE VALVES PERFORM FUNCTIONS OTHER THAN SEALING COMPRESSION
The valves in an engine have numerous functions. First, they must permit the intake of fuel and air. Then they must seal compression. After the explosion the exhaust valve must permit the burned gases to leave the combustion chamber. Then there is one other function that valves must perform. They must streamline these gases and make it possible for them to move into and out of the combustion chamber as rapidly as possible, and, when the gases leave the combustion chamber, they must be so directed that they will not swirl or congest in a manner that will prevent the complete scavenging of the cylinder. The terrific pressure at which the gases pass through the exhaust manifold will normally create a vacuum in the cylinder, which in turn will assist in the complete scavenging of the cylinder.
Years ago, before engines operated at a high rate of speed, the matter of streamlining the gases was not considered an important one. When it is considered that at an average speed of fifty miles per hour there are twenty intakes, twenty explosions and twenty exhausts in each cylinder every second, it is not difficult to realize the importance of streamlining the gases. Automotive engineers today recognize this and in many instances have changed the shape of the valve towards the tulip design or designed them with a large fillet on the under side of the valve. The purpose of this fillet is to streamline the gases so they will pass freely out of the exhaust manifold. Most poppet valves are made at an angle of forty-five degrees, and being round they permit, (provided the valve is properly aligned), the exhaust gases to rush towards each other in a circle and under terrific pressure at an enormous velocity. This actually creates a vacuum that completely scavenges the cylinder. If the gases are not guided by the fillet under the valve, they collide and swirl, so to speak, which will cause a congestion in the manifold. This congestion will work against the proper elimination of the gases.
DO NOT ALTER SHAPE OF VALVE PORTS
For this reason service mechanics should avoid cutting away the port below the valve seat and should be very particular not to destroy the radius that may be above the valve seat in diesel- type engines especially. This radius was placed there for a purpose by the designer of the engine.
MISALIGNMENT OF VALVES AND VALVE SEATS AFFECTS STREAMLINING OF GASES
Inasmuch as the shape of the valve and stem have the effect of streamlining the gases, a valve that is misaligned or a valve seat that is distorted by unevenly tightened head bolts will very seriously affect the operation of an engine. The timing will be changed as a result of the valve contacting the high portion first, then later being pulled into contact with the seat by the tension of the spring. The time that elapses between the contacting of the high spot and of the valve being pulled into contact with the seat, while of exceedingly short duration, is really of considerable importance, due to piston travel. Consider an exhaust valve that has been misaligned, or a valve seat that has been distorted by lack of torque control whereby the valve contacts one side of the seat first. This causes the valve to cool more quickly on that side — contracting the fillet — causing the valve to press harder on the seat at one point while the remainder of the valve is cracked open. It is common for such a crack to be opened as wide as .015 of an inch. Therefore, the hot gases rushing out of the combustion chamber pass a portion of the valve only, cause the fillet to expand on that particular side which opens the orifice even wider, further maligning the valve.
Since the gases that pass this leak do not meet the gases that should pass from the side that is closed, they strike the exhaust manifold on one side causing the stream of gas to swirl (see page 11). This will cause a congestion which will prevent the complete scavenging of the cylinder, so that when the piston
reaches the top of the scavenging stroke, there will be a slight compression in the cylinder. This can be compared to turning a high-pressure hose into a drain in a basin. The stream striking the bowl "head-on" will swirl or boil and the basin will fill up and run over. By directing the stream slightly to one side, it will be found that the drain will take care of the flow of water satisfactorily. It is obvious, therefore, that the piston will have to travel partially back down again to relieve this slight compression before the intake of gas can begin (see page 14). This would be the equivalent of shortening the stroke of the engine, with the resulting loss of power, to say nothing of the results that would arise from exhaust gases being left with the combustible mixture that is drawn in with the intake stroke.
This shows the piston at "Bottom Dead Center" just at the beginning of the exhaust stroke. The misaligned exhaust valve is causing the gases to begin to swirl which will cause a congestion in the exhaust manifold and prevent proper scavenging of the cylinder.
This shows the distance of piston travel during the first 45° of exhaust stroke. It also shows the ideal condition with valves in correct alignment. Note the streamlining of exhaust gases for rapid and complete scavenging of the cylinder.
This shows a warped exhaust vaive fully open, intake valve closed, at the beginning of the last 45° of the exhaust stroke. The continued swirl of gases in the exhaust manifold is retarding the rapid scavenging of the cylinder.
Distance of piston travel at the first 45° of intake. Congestion in the exhaust manifold has prevented complete scavenging, leaving a slight compression in the cylinder. The piston must, therefore, move slightly downward to relieve this compression before intake of gas can begin. This is equivalent to shortening the engine stroke.
The piston keeps on Traveling while the valve is sliding improperly off or on the seat
A piston may have completed one-fifth of its travel by the time the misaligned exhaust valve completely contacts the seat. In an ordinary engine a valve is lifted about .001" by the cam, while the fly wheel is traveling from two to three degrees, depending upon the make of the engine. If the valve is cracked open as much as .015" on one side, we therefore would have a piston travel of three degrees times .015", or forty-five degrees of crank travel. Consider this in connection with the fact that when a car is moving at the rate of fifty miles per hour, the reciprocal action of the piston is approximately twenty times a second, and when the valve port is not entirely open all the way around, the piston goes to the top, creates a slight compression as has been previously described, and will return approximately a distance represented by forty-five degrees of crank travel before intake gases can enter the cylinder.
RESULT OF LATE VALVE ACTION
In case of extreme misalignment of both intake and exhaust valves, some of this slight compression in the cylinder may be forced into the intake manifold causing pre-ignition. This is noticeable at higher speeds and is indicated by an occasional cough or backfire of the engine.
Definitely, there is much more to a valve's performance than the function of sealing compression. On one of the popular makes of engines, when the crank pin moves from top dead- center to a point equal to forty-five degrees, the piston has traveled down approximately twenty percent of its entire stroke. The piston in the same engine when moved forty-five degrees from the bottom dead-center will travel up only thirteen percent of its stroke. In other words, the piston is moving a greater distance at forty-five degrees of travel from top dead-center (see page 14), than it does in the same distance from bottom dead-center (see page 12), and it is when the piston is at the top that the exhaust valve is closing and the intake valve is opening. If you will consult late "Valve Timing Data," you will find that in some of the engines the intake valve opens twenty-six degrees before top dead-center and in the same engine the exhaust valves close at thirty-four degrees after dead- center. This means that both valves are open at the same time for a period of sixty degrees.
When these factors are taken into consideration, it must be admitted that misalignment of .001 of an inch on a valve is one of the most important dimensional elements in an engine.
Actual tests have proven that if the ordinary valve struck the valve seat on one side .001" sooner than it did on the other, it would take .010" of clearance between the valve stem and the guide at the bottom of the valve guide to let the valve rest on the opposite side of this seat without bending the stem. Truly then, valve alignment is exceedingly important.
Many service shop operators claim they are perfectly satisfied with the results they are getting. They also claim they are having no trouble. They may not be having trouble, but the owners of the engines they service do have trouble. In most instances they do not know where the trouble exists or where to place the blame, because they have never learned that engine performance can be restored to the equivalent of new after an engine has been run for some time. Many mechanics think because they have .002" or .003" clearance between a valve stem and valve guide they have that much to play with as the valve stem when cold is .003" and sometimes .004" smaller than the hole in the valve guide. This clearance was left there by the engineer to allow for expansion of the valve stem at the top of the guide so there will only be room for a film of oil when the engine is warm and running. There are engines that employ valve guides tapered as much as .004 of an inch, but it was the intention of the engineers that this clearance be reduced to normal clearance when the valve stem itself becomes heated and expands.
PROPER ALIGNMENT ESSENTIAL
In correcting a warped or misaligned valve so it will function properly when placed in an engine, the valve face must be restored to concentricity with the center line of that portion of the stem that operates in the valve guide. Wet grinding is considered a necessity for today's valves and all newer valve facers include a coolant system.
The above illustration shows the effect of holding a valve in a chuck that grips the end of the stem in a cone, and, as indicated by the check marks, in the distorted portion above the guide travel. A valve chucked in this manner cannot be refaced concentric with its original center. Note the valve face is eccentric to the center line of the stem. It is impossible for such a valve to seal compression.
In this illustration we have the effect of holding a valve in a chuck that grips it only on the distorted portion, as indicated by the four check marks. Note the true center line "AB" and the false center line "CD" established by this refacing operation. As this valve is refaced at a tangent to the true center, it will leak compression.
To properly correct a warped or distorted valve it is necessary to grip the valve stem in two places, with a three-point grip, within that portion of the stem that operates in the guide, as shown in this illustration. We know of no other way of accomplishing the proper results. Note that this finished valve face is concentric with the true center line of the valve. The shaded portion "E" shows metal removed. The Kwik-Way Chuck (illustrated below) was designed to accomplish these results. While it has been imitated in many ways, it has never been definitely copied.
Any valve face that is not concentric with the part of the stem that operates in the guide will contact the valve seat on only a small portion of its circumference. It will slap, bounce, be noisy, leak compression and affect valve timing. A properly corrected valve will contact the valve seat throughout its entire circumference and the valve stem will "float" in the guide, free from valve stem friction. Fuel economy and utilization of all possible power will be the result.
The fact that the use of grinding compound will not secure effective results in a valve reseating operation has been accepted for a number of years by the authorities in the industry. It is possible, through the use of compound, to effect a joint between the valve and the valve seat when the engine is cold, but as soon as the valve becomes heated from the natural heat of the engine, the portion that has been ground with compound will not contact the seat due to expansion of the metal. Here is the reason why.- A valve head 2" in diameter heated to 1450° (the normal temperature of an exhaust valve in operation), will expand .016", or .008" from each side of center. This means the valve will rise on the seat. The illustration below shows a valve and seat "ground in" with compound. When the engine is cold the valve and seat apparently form complete contact; but when the valve is heated and has raised, the portion ground in with compound is actually not in contact with the seat at all, and it is impossible for it ever to be when the engine is functioning. Through the use of the Kwik-Way Tapered Arbor for aligning a valve reseating operation, a compression-tight joint may be secured between the valve and the valve seat and this joint will be effective whether the valve is hot or cold. The use of compound on a valve so realigned would really prove detrimental.
Diesel engines occupy a very important position in the service field today. Knowledge of diesel engines should be acquired by everyone in the service industry and as rapidly as possible. In diesel engines of the two-cycle type any tendency for the burned gases to collide or swirl as they are passing out will delay the expulsion and carry the timing over to a point where harmful results will occur, since in this type engine there must be a complete intake of fresh air, compression and ignition in one revolution of three hundred and sixty degrees. In addition, the burned gases must be expelled from the cylinders and the exhaust valve cooled for the next operation. The exhaust valves are cooled while resting on the seat. It is interesting to note that the exhaust valve in a two-cycle engine has sixty per cent less time allowed for cooling than the valves in a four-cycle engine.
A check-up was recently made of a two-cycle diesel engine used in transportation service. This particular engine was operating on a fuel consumption of approximately forty gallons per hour at wide open throttle and at full load, whereas the engine was rated to perform satisfactorily under these conditions on about nine gallons per hour. The engine had been in service intermittently for twenty-three days. As a theoretical analysis of the reason for excessive fuel consumption, let us consider the following:
Upon removing the cylinder heads it was found that the misalignment of the seats was about .01 6". The misalignment of the valves was not checked. Excessive consumption of fuel was the result of valve and valve seat misalignment. The injectors were checked and found to be o.k. Compression appeared normal and the blowers to scavenge the cylinders were producing their normal pressure to blow the burned gases out of the cylinders. In this particular engine the fuel injections take place at 5° ahead of center at an idle speed. The power stroke is complete at about 100°, at which time the exhaust valves open in the cylinder head to permit blowing off the terrific pressure in the cylinder. The exhaust valves are open for a period ofVALVE TIMING OF A 2 CYCLE DIESEL ENGINE
137°. About fifty times the normal capacity of the cylinder at atmospheric pressure in compressed gases has to be eliminated through the exhaust valves, since the piston travels down to expose ports in the cylinder and admit air for scavenging. These ports are open 50° each side of the bottom dead-center. From the time the exhaust valves open and the air ports are exposed by the piston traveling downward, 30° of crankshaft travel has taken place. In other words, when 130° is reached on the crankshaft, the piston has traveled down and exposes the ports in the cylinder and admits air to scavenge the cylinder. These ports are closed by the upward movement of the piston. Then the exhaust valves close and the piston travels up, compressing the gases at a ratio of about sixteen to one.
This particular engine had a maximum r.p.m. of seven hundred and twenty. This means that it made one revolution in 1/12 of a second, and since thirty degrees is 1/1 2th of a revolution, then the equivalent time allotted to blow off the high pressure was equal to 1/144th of a second.
The manufacturer's valve chart shows that the exhaust valves open .008" during six degrees of crank-shaft travel. Therefore a valve that was misaligned .016" or twice .008" would equal approximately twelve degrees of crank travel, partially delaying the opening of valves. Twelve degrees from thirty degrees leaves eighteen degrees, and eighteen degrees would equal 1/240th of a second instead of 1/1 44th as it should have been. In the design of this engine thirty degrees was considered ample time to blow off the high pressure gases. It is obvious if there is any pressure in the cylinders when the ports are exposed that the gases will blow out into the air manifold if the pressure is greater than the pressure in the air manifold or the amount maintained by the air blower. (The air blower maintains a pressure of only three pounds.)
If some of these gases are trapped in the cylinder due to the delay when the exhaust valves close, then if the engine travels around until it gets the next injection of fuel and the resultant explosion is not ample or sufficient due to faulty mixture, the governor will open the injector and admit more fuel. It will explode again on the next revolution and if it still lacks sufficient power, the fuel will be increased more and more which will throw the ratio out of proportion and increase the fuel consumption to a point that will be prohibitive. Since the fuel is coming into the cylinders from one place and the air from another, a very bad situation can occur that would not take place in a four-cycle carbureted engine.
This illustration tends to show the enormous volume of gas that is compressed into the cylinders of a diesel engine — about fifty times the normal capacity of the cylinder at atmospheric pressure.
Remember that the valve seats in this particular engine were misaligned at an average of .016" each. The misalignment of the valves was not checked. With the Kwik-Way System of Scientific Valve and Valve Seat Correction, the valves and valve seats in this engine were restored to proper concentricity and alignment, which sealed compression at the valves. As a result the fuel consumption was restored to the manufacturer's rating which was only about one-fourth of the fuel that had been used during the period of valve misalignment.
It can be definitely seen that if valve misalignment will cause a diesel-type engine to increase fuel consumption from a rated nine gallons per hour to forty gallons per hour, this same condition will to an equal or less extent affect other engines of the diesel type. Again, use of a torque wrench to tighten cylinder head bolts or nuts is necessary to insure against block distortion which can cause misalignment and valve seat distortion.
The engine of today is a marvel of perfection. It will perform satisfactorily in temperatures ranging from one hundred and twenty degrees above zero to from twenty to forty degrees below zero. It has fast acceleration and speed beyond the margins of safety and thousands of miles of satisfactory service. But it has been truthfully said that the engine has not been built that cannot be improved by the service that may be rendered by a well-trained mechanic who uses the proper equipment.
Kwik-Way Products Inc.
PRECISION ENGINE RECONDITIONING EQUIPMENT INCLUDES
- VALVE FACERS
- VALVE SEAT GRINDERS
- CYLINDER BORING BARS
- ENGINE BORING FIXTURES
- SURFACE GRINDERS
- BRAKE SERVICE EQUIPMENT
Copyright 1948, all rights reserved
Kwik-Way Products Inc.,500 57th St., Marion, Iowa
Revised Edition 1979