5 Ways to break the nose of a crankshaft

 

1. IMPROPER MACHINED CRANK GEARS

A.  Champher machined at wrong angle.

 B. Champher machined with too small an angle.

 C. Belt drive gears.

The seal sleeve bottoms to the face of the main before the interface of the gear bottoms against the step in the nose of the crank. All of the above prevents the crank gear from bottoming against the step on the nose of the crank. This leaves a gap between the gear and the step, which allows the crank to flex …A fatigue crack starts. SNAP!!!! The crank breaks.

 2. DAMPERS WITH MOVING INERTIA WEIGHTS

 Fluid, balls, springs, inertia rings with rubber O-Rings, etc. Can you balance a wheel on your race car if the tires are flat???? How can your rotating assembly be balanced if to quote one manufacturer,” These units (Dampers) should not be on the crank for balancing as the inertia weight may not be centered until the engine starts. “NEWS FLASH” Centrifugal force will always take the inertia weight off center no matter what RPM. Your assembly is never balanced. “TELL TALE SIGN” Metal transferred on nose outside diameter and damper internal diameter …A fatigue crack starts. SNAP! The crank breaks.

 3. EXTERNAL BALANCE vs. RPM

 Rotating weight multiplies as RPM increases. Engines have heavier or lighter balance weights and larger or smaller noses. RPM above 5500RPM is more risky on a Small Block Chevy than a Big Block Chevy. However, as RPM’s go up, the weight more and more wants to leave the crank due to centrifugal force. Do not be surprised if at some point fatigue sets in and the nose comes off.

 4. DRIVES EXTENDING BEYOND THE NORMAL DISTANCE ON THE NOSE

Multi-stage oil pumps, blowers, etc all have belt drives that require torque taking off at 90 degrees to center line of the crank. More torque is necessary for driving these things and further away from main bearing support all leads to multiple of leverage wiggling the nose. Fatigue sets in, nose breaks, blower stops. The Small Block Chevy has the smallest diameter nose and the weakest of all. Note: Blowers take substantially more 90 degree torque than dry sump pumps, therefore, more likely to break noses. Not recommended for Small Block Chevy. If a blower is being used, use a crank with a Big Block nose.

 5. IMPROPER BALANCING TECHNIQUE

 The counterweights on a crankshaft are designed to work all together as a system within a certain bob weight range. To correct the balance on a crank where the counterweights are too heavy the following should be followed: Internal Balance: If more than 2 holes are required in each end, the outer diameter of all the counter weights should be turned in a lathe to correct the out of balance condition in all the counterweights. If you try to drill more holes, you will create a secondary wave which will lead to crank flex and eventually a fatigue crank. External Balance: The crank is spun with the external balance and flywheel. If it is determined that the assembly is too heavy where the weight is on the damper and flywheel, do not make the correction on the end counterweights of the crank. The out of balance condition is in the damper and flywheel, which is where it should be corrected. It is very simple to alter the bolt on weight of the damper and drill the balance weight on the flywheel. If these components need to be replaced simply bolt on the proper weight to the damper and match balance the flywheel which has to be balanced anyway. If you correct in the end counterweights, you will create a wave in the crank which will wiggle the nose of the crank which well eventually start a fatigue crack which will snap the crank.

 

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Cast, Hypereutectic or Forged Pistons

Cast Pistons

 

A cast shaped component means that the material has been melted and then poured into a mold that basically shapes the piston. The advantages are many, for example: a possibility to add other components like silicone, carbon, zinc and so on in order to gain certain properties. The aluminum itself doesn’t build up inner tension as much. It is cheap. The density of the material doesn’t increase which means it could be kept light.

There are disadvantages also, of course. The piston will be weaker in structure. It is often heavier since the manufacturer has to increase wall thickness in order to achieve sufficient strength. The heat expansion cannot be controlled and is therefore often not completely round since the piston pin requires some material on the inside. They are also produced in bulk with most manufacturers only producing sizes that are close to factory specifications. This also makes them more affordable.

 

Hypereutectic Pistons

 

“Hypereutectic” means over eutectic. The word eutectic refers to a condition in chemistry when two elements can be alloyed together on a molecular level, but only up to a specific percentage, at which point any additional secondary element will retain a distinct separate form.

Although internal combustion engine pistons commonly contain trace amounts (less than 2% each) of copper, manganese, and nickel, the major element in automotive pistons is aluminum due to its light weight, low cost, and acceptable strength. The alloying element of concern in automotive pistons is silicon.

Silicon in this context can be thought of as “powdered sand”. Any silicon that is added to aluminum above a 12% content will retain a distinct granular form instead of melting. At a blend of 25% silicon there is a significant reduction of strength in the piston alloy so stock hypereutectic pistons commonly use a level of silicon between 16% and 19%. Special molds, casting, and cooling techniques are required to obtain uniformly dispersed silicon particles throughout the piston material.

The biggest drawback of adding silicon to pistons is that the piston becomes more brittle as the ratio of silicon is added. This makes the piston more susceptible to cracking if the engine experiences pre-ignition or detonation as well as when power adders are installed. Performance replacement alloys.

When auto enthusiasts want to increase the power of the engine they may add some type of forced induction. By compressing more air and fuel into each intake cycle, the power of the engine can be dramatically increased. This also increases the heat and pressure in the cylinder.

The 4032 performance piston alloy has a silicon content of approximately 11%. This means that it expands less than a piston with no silicon, but since the silicon is fully alloyed on a molecular level (eutectic), the alloy is less brittle and more flexible than a stock hypereutectic “smog” piston. These pistons can survive mild detonation with less damage than stock pistons.

Aftermarket performance pistons are most commonly made from 4032 and 2618 alloys and are typically forged. The 2618 performance piston alloy has less than 2% silicon. This alloy is capable of experiencing the most detonation and abuse while suffering the least amount of damage.

 

Forged Pistons

 

 

Forged pistons are mechanically shaped into a piston shape. They are hammered, pressed (forged) into a mold forming the piston in turn removing any possible porosity and also pushes the alloy grains together tighter than can be achieved by simple casting alone. The result is a much stronger material.

By utilizing state-of-the-art CNC machines, most manufacturers can maintain exact specifications and tolerances. This makes them structurally more durable. Forged pistons are well known in the racing and performance industry because of their ability to withstand more heat, higher RPMs, higher boost and higher temperatures. But forged pistons are not just for professional racers. Another advantage to a forged piston is that they can be individually made to any custom size or specification without the high cost of casting.

The choice between using a Cast, Hypereutectic or Forged piston is dictated by the application. Forged pistons may not be absolutely necessary in all applications. However, the minor additional cost of a forged piston can save your motor from disaster in a marginal situation.

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WET SUMP vs DRY SUMP

There are two major divisions in engine oiling systems: wet and dry sump. “Sump” simply means the chamber in the bottom of any engine that collects lubricants for redistribution. In a piston engine the oil pan is the sump. A wet-sump system is the same used in passenger cars and mostly seen in the lower levels of racing. Wet sump means engine oil is collected and stored in the oil pan until it is recirculated by the oil pump back through the engine. In a dry-sump system oil is collected in the oil pan and immediately sucked, or “scavenged,” to an external tank before being recirculated to the engine. Because the sump is not used to store oil, it is referred to as “dry.”

A dry-sump system has several advantages over wet, but the main one is additional power. Because there is only a minimum of oil in the pan, windage—oil clinging to or splashing against the rotating assemblies of the engine—is greatly reduced. In addition to evacuating oil from the pan, the external oil pump creates a vacuum inside the pan and block that further increases horsepower by improving ring seal. Other advantages of a dry-sump system are increased oil capacity because of the external tank, the ability to easily add remote oil coolers, and because the pan doesn’t store oil, it can be quite shallow to allow for lower engine placement.

A wet-sump system is simple, low cost, and light weight. That’s why virtually every production engine in the world uses wet-sump lubrication. A dry-sump system is more complicated, more expensive, and heavier, but it offers continuous lubrication under all conditions and the promise of increased power through reduced windage.

When you consider cost and complexity, a wet-sump oil system is the logical choice for most Sportsman racers. The biggest mistake a Sportsman racer can make, however, is to try to duplicate the performance characteristics of a dry-sump using a wet-sump system. This can’t be done without sacrificing reliability.

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Auto Math 101

CUBIC INCH DISPLACEMENT

BORE X BORE X STROKE X .7854 X # CYLINDERS

4.030 x 4.030 x 3.750 x .7854 x 8 = 382.6 ( 383 Chevy )

 PISTON TO DECK CLEARANCE VOLUME

 BORE X BORE X 12.87 X PISTON TO DECK CLEARANCE [ PLUS OR MINUS ]

                   EXAMPLE:   4.030 X 4.030 X 12.87 X .009 = 1.88cc

 COMPRESSED GASKET VOLUME

 BORE X BORE X 12.87 X COMPRESSED GASKET THICKNESS

EXAMPLE: 4.030 X 4.030 X 12.87 X .030 = 6.27cc

 NET COMBUSTION – CHAMBER VOLUME

 1. DOME PISTON EQUATION

NET COMBUSTION CHAMBER VOLUME = COMBUSTION CHAMBER VOLUME–PISTON DOME  VOLUME + [PISTON DECK CLEARANCE + COMPRESSED GASKET THICKNESS]

 EXAMPLE:    64cc HEADS, 12cc DOME PISTON, 1.88cc OF PISTON TO DECK CLEARANCE AND 6.27cc OF COMPRESSED GASKET VOLUME 

64-12=52

1.88+6.27=8.15

52+8.15=60.15cc

NOTE: ALL CALCULATIONS MUST BE IN cc’s

 2.  DISHED OR FLAT TOP PISTON EQUATION NET COMBUSTION CHAMBER VOLUME = COMBUSTION CHAMBER  VOLUME + PISTON DISH OR VALVE POCKET VOLUME + PISTON DECK CLEARANCE + COMPRESSED GASKET THICKNESS

 EXAMPLE: 64cc HEADS, A-12cc PISTON DISH OR VALVE POCKET, 1.88cc  OF PISTON TO DECK CLEARANCE AND 6.27cc  OF COMPRESSED GASKET VOLUME

64cc + 1.88 + 6.27 =84.15cc 

NOTE: ALL  CALCULATIONS MUST BE IN cc’s

  COMPRESSION RATIO

 { CUBIC INCH DISPLACEMENT} ÷ {# CYLINDERS} x {16.39} ÷ {NET COMBUSTION CHAMBER VOLUME}+ 1

EXAMPLE: DIVIDE 355 BY 8 = 44.375

MULTIPLY 44.375 BY 16.39 = 727.306

DIVIDE  727.306 BY YOUR NET COMBUSTION  CHAMBER VOLUME, LETS SAY IT’S 60.15 = 12.09 add 1

YOUR COMPRESSION RATIO WOULD BE 1309-1

BORE /STROKE RATIO

 BORE ÷ STROKE

EXAMPLE: 4.030 ÷ 3.48 = 1.158

 ROD RATIO

 CONNECTING ROD LENGTH ÷ CRANKSHAFT STROKE

EXAMPLE: 5.700 ÷ 3.489 = 1.637    

PISTON SPEED

 STROKE  IN INCHES X RPM ÷ 6

RESULTS MEASURED IN FEET PER MINUTE

EXAMPLE: 3.48 X 6000 ÷ 6 = 3480 FPM

 CARBURETOR CFM

 BIGGER IS NOT ALWAYS BETTER

WE MUST KNOW THE THEORETICAL AIR CAPACITY TO DETERMINE THE VOLUMETRIC EFFICIENCY

 

THEORETICAL  CFM = RPM X DISPLACEMENT ÷ 3456

 VOLUMETRIC EFFICIENCY = ACTUAL CFM ÷ THEORETICAL CFM X 100

 STREET CARB. CFM = RPM X DISPLACEMENT ÷ 3456 X .85

 RACING CARB. CFM = RPM X DISPLACEMENT ÷ 3456 X 1.10

CAM LIFT vs. GROSS VALVE LIFT

CAM LIFT  OR LOBE LIFT X ROCKER RATIO = GROSS VALVE LIFT

THIS LEADS ME TO THE NEXT  FORMULA TO DETERMINE MY GROSS VALVE LIFT IF I CHANGE MY ROCKER RATIO SUCH AS , INSTALLING 1.6 SBC ROCKERS WITH A COMP. CAMS XTREME ENERGY # XE 268H CAMSHAFT. CURRENT LISTING STATES .477/.480 LIFT w/1.5 ROCKERS

 VALVE LIFT ÷ ROCKER RATIO = LOBE LIFT [ CAM LIFT ]

LOBE LIFT X ROCKER RATIO = GROSS VALVE LIFT

EXAMPLE: .477 ÷ 1.5 = .318 [ LOBE LIFT ]

.318 X 1.6 = .5088 [ GROSS VALVE LIFT ]

NOTE: IF THE CAM HAS A DIFFERENT LIFT FOR THE EXHAUST, USE THE SAME FORMULA FOR THE EXHAUST. ALL OTHER SPEC’S  FOR THE CAMSHAFT REMAIN THE SAME.

 THEREFORE THE COMP.  CAMS #XE 268H USING 1.6 ROCKER RATIO PRODUCES .508/ .512 LIFT.

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Quick Reference – “Bore Spacing”

Bore spacing is the distance from the center line of one cylinder bore to that of the adjacent cylinder. Assuming the bores are perfectly round, this distance can be determined by measuring the distance from one cylinder wall edge to the far cylinder wall of the adjacent cylinder. To save all of our Bessel Motorsports readers the trouble, here’s the bore spacing (in inches) on common American V8’s:

 

• AMC: 4.75
• BUICK 350: 4.24
• BUICK 400-430,455: 4.75
• CADILLAC 472, 500: 5.00
• CHEVY SMALL BLOCK: 4.40
• CHEVY BIG BLOCK: 4.84
• MOPAR SMALL BLOCK: 4.46
• MOPAR BIG BLOCK: 4.80
• FORD SMALL BLOCK: 4.38
• FORD FE: 4.63
• OLDSMOBILE: 4.625
• PONTIAC: 4.62

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Crankshaft Tech – “SAY NO TO CROSS – DRILLING”

Nowhere is this more true than in the straight shot oil systems designed into all Bessel Motorsports crankshafts. With the throw at 12:00 the oil enters the main bearing between 6:00 and 9:00 depending on journal size and stroke. The oil passage goes straight to the throw and exists at approx 1:30 to 2:00. RPM of the crankshaft unlike cross-drilling has no effect on oil delivery to the throw.
What is cross-drilling?
Cross drilled cranks have oil feed holes drilled completely throughout the journals. Sometimes mains only and sometimes mains and throws. An angle hole is then drilled from the throw to the main on the centerline of the crank. Some think this system, because both ends of the cross drilled hole are exposed to oil supply, will ensure continuous supply of oil to the rod journal.
WRONG
Pressurized oil must enter the main journal and overcome centrifugal force of rapid acceleration or RPM to reach the center of the crank before the oil can travel to the throw. Only increased oil pressure will overcome the “crack the whip effect”. In most cases it will not and the result is a very expensive rod failure. You do not see any NASCAR team using cross-drilled cranks.
Bessel Motorsports commitment:
We are committed in selling only the highest quality crankshaft and WILL NOT cross drill crankshafts even though the process is easier and less expensive.

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Stroker Kits 101

A Stroker kit is an aftermarket assembly that increases the displacement of a reciprocating engine by increasing the travel of the piston (that is, the piston moves further up and/or down in the cylinder). This is done by using a different crankshaft where the crank pin is moved further away from the center of the axis of rotation of the crankshaft. While this increases displacement and torque it can potentially lower the limit to which the motor can rev safely compared to the stock configuration.

10 RULES FOR SUCCESSFUL STROKER BUILDS

• Select as long as a rod as possible to minimize the frictional losses from side loading and cut the engine’s mechanical noise.
• Select the lightest reciprocating components for the bottom end.
• Use an effective crank damper
• Use an oil pan that keeps the oil away from the bottom end rotating assembly as entertainment will cost big power and may lead to failure.
• Go for as high a compression ratio as possible as it will off-set the engine’s reduced mechanical efficiency due to it’s greater piston friction.
• Use cylinders heads with valves as large as possible as there are a lot more cubes to feed.
• Be sure to tighten up the cam’s lobe centerline angle (LCA) from whatever was optimum before by about 1 degree for every 16 cubic inches of capacity increase.
• Increase valve lift at least the same proportion as the increase in displacement.
• Make sure the induction system has enough flow capability to handle the extra cubic inches.
• Try to keep the induction system cool as this makes more difference with a stoked engine.

We offer both Cast and Forged options. All rotating assemblies come with .030″ over bore pistons, unless otherwise indicated.If you require a different bore, please advise your sales representative. In addition, we offer Lightweight Pro Comp & Superlight assemblies.

All of the stroker kits from Bessel Motorsports include the following

• Crankshaft
• Connecting Rods
• Pistons
• Rings
• Rod & Main Bearings

    A typical complete stroker kit is comprised of the crankshaft, connecting rods, pistons, piston pins, main bearings, rod bearings, and piston rings. This assembly is also called “the rotating assembly” or “the bottom end”. Many different types of each of the components can be used for different applications. Crankshafts, for example, may be either of forged or of cast manufacture. Rods may consist of I-beam or H-beam rods made of various materials, from steel to titanium. Rods may be stock length (requiring the use of either shorter pistons, or taller cylinders), or shorter length (usually utilizing stock height pistons and cylinders).

Bessel Motorsports is dedicated to the serious street / strip racers and week-end warriors that are interested in purchasing a high performance stroker kits and racing parts for their race cars. Strokerkits.com has reached thousands of Street/Strip racers with reliable and reasonably priced stroker kits. For the hard core racer we also handle billet steel cranks, rods, and custom made pistons.

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