How to Build Horsepower with a Small-Block Chevy: Connecting Rods - Chevy DIY (2023)

Today’s Small-Block Chevy aftermarket offers a mind-boggling selection of rods in terms of superior materials, design innovations, lengths, and bearing bore diameter sizes to accommodate any build that you desire.

Rod ratio is the combination of crankshaft stroke and connecting rod length. The ratio created by this combination affects both performance and durability. Rod ratio needs to be considered. Rod ratio is calculated by dividing the rod length by the crank stroke. For example, if the crankshaft features a stroke of 4.000 inches and the rod length is 6.000 inches, 6.000 divided by 4.000 equals a 1.5:1 rod ratio.

By increasing the stroke or by using a shorter rod, the rod ratio decreases. If the stroke is reduced or a longer rod is used, the rod ratio increases. Changes in the rod ratio affect the operating angle of the rods, which in turn affect piston thrust load and friction between piston skirts and the cylinder walls. Generally speaking, for street and high-performance use, rod ratios in the 1.5 to 1.8:1 range are acceptable, and about 1.75:1 is considered by some as ideal. However, extreme performance applications sometimes use ratios as high as 1.9 to 2:1.

When generically discussing rod length, let’s compare 5.700-inch rods to 6.000-inch rods while keeping the crank stroke unchanged. A shorter rod causes the piston to spend a bit less time dwelling at top dead center (TDC). A longer rod causes the piston to dwell longer at TDC, resulting in greater combustion pressure. A 5.700-inch rod allows the piston to dwell for about 2 to 3 degrees at TDC, while a 6.000-inch rod allows the piston to dwell at TDC about 9 to 10 degrees. The longer dwell time with a longer rod helps to flatten out the torque curve and allows the use of a higher compression ratio on pump gas. A longer rod aids the engine to pull better in a high RPM range.

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Connecting rods are one of the most critical components for any performance build. They provide the connection between the crank and the pistons and must withstand compression force and the dynamics incurred during the transition between approaching TDC and leaving TDC. Tensile strength, rigidity, and weight considerations are key factors. For engines designed to produce high levels of both horsepower and torque, only high-quality aftermarket forged steel, aluminum, or titanium rods should be considered. Cast rods should be completely ignored.

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Factory OEM rods in the past typically required machining or grinding to create a weight-matched set. Current aftermarket performance rods commonly require little, if any, weight corrections.

The use of a longer rod also allows the use of pistons with a shorter compression distance (distance from the wrist pin centerline to the dome), which allows for a shorter skirt length, reducing weight mass. In basic terms, a longer rod provides more torque at high RPMs and reduces friction due to the reduced operational angle compared to a shorter rod.

All things considered, what is the best stroke and rod length combination? It all depends on your objectives.

Both OEM and aftermarket blocks are available in standard 9.025-inch deck heights, in addition to a variety of tall-deck configurations. Using Dart as one example, deck heights of 8.850, 9.025, 9.325, and 9.500 inches are available.

When determining the rod length that fits your build, you must consider these factors:

    • Block deck height
    • Half of the crank stroke
    • Piston compression height

The reason we are only concerned with half of the crankshaft stroke when determining rod length is because only the TDC location of the crank rod journal influences the placement of the piston dome relative to the block deck. So, if the crank features a 4.000-inch stroke, we only factor in one half of the total stroke, which in this case is 2.000 inches. The half-stroke dimension, coupled with rod length and piston compression height, combines to place the piston dome at the block deck, whether this is desired at zero or slightly below deck according to the builder’s plan.

While rod ratio is certainly a factor to consider, other factors, such as displacement, compression ratio, cylinder head flow, cam timing, and exhaust scavenging, play a bigger role.

Types of Rods

If you’re planning to build a killer small-block Chevy, or any serious-performance engine for that matter, forget factory rods. Spend the dough on a set of high-quality aftermarket rods. Today’s rod makers use superior materials for strength and durability with higher-precision machining and typically offer rods that are spot-on in terms of dimensions and weight-match.

Since stroke increases are so popular, leading rod makers have addressed this by featuring lower profiles at the top shoulders of the rod for clearance. This eliminates the need to modify the rods to gain needed clearance at the pan rails and cylinder bottoms.

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Forged Steel Rods

Today’s forged steel rods are made by heating a dense ingot of alloy steel (commonly using 4340 steel) to a malleable state at about 2,200°F, then forming the raw part under as much as 240,000 pounds of pressure in a forging die. The forging process results in an extremely strong unit with a tight molecular grain, which is followed by heat treating and stress relieving. This makes the metal stronger with a tighter, more-compacted grain structure. Depending on the rod maker, the rods may then be induction hardened, shot-peened, and/or cryogenically stress-relieved and heat treated.

The trimmed, rough-shape forging is then quenched and tempered. Heat treating should be done before machining because the heat treating/ tempering process can deform the part’s shape by as much as 0.060 inch. Manufacturer methods may vary but might involve quenching the part in a glycol solution. The raw rod is then CNC machined, the raw cap is cut away, both mating surfaces are machined to create a light undersize, the cap is installed, and the big end is machined to create a perfectly round hole at a precise diameter. Once machining is complete, the rod is stress relieved and surface hardened.

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Note the contoured/low profile of the upper rod bolt shoulders. Aftermarket rod makers are aware of the need to accommodate increased stroke, offering this design to provide additional clearance. This is an example of a Scat stroker rod.

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A set of Oliver Racing Parts I-beam steel rods is shown here. High-quality aftermarket rod makers offer tightly weight-matched sets. I-beam steel rods generally offer lighter weight and are more suited for high engine speeds. With that said, excellent results can be had with either beam design in terms of both high revs and torque handling capability. In many cases, the choice of beam design is dictated by a builder’s personal preference. (Photo Courtesy Oliver Racing Parts)

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Commonly available beam designs include H-beam and I-beam. Examples of I-beam rods are seen here. Beam design preference is often the result of the opinion and/or experience of the individual builder. Rods of both designs made by reputable manufacturers offer high tensile strength.

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While most OEM rods feature press-fit wrist pins where the pins float but are press-fit to the piston pin bosses, aftermarket piston makers and rod makers offer full-floating pin designs where the pins freely rotate in both the rod’s small end and piston. Some rod makers offer a choice of press or float applications. An oil-fed bronze bushing is featured in the rod small-end bore for enhanced lubricity.

How to Build Horsepower with a Small-Block Chevy: Connecting Rods - Chevy DIY (8)

In a further effort to both reduce weight and increase strength, aftermarket rod caps often feature a ribbed design.

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Aftermarket performance rods are chamfered at the side of the rod that faces the crankshaft’s rod journal radiused fillet. Because performance cranks feature a generous radius fillet at each end of the journal, this chamfer accommodates the needed clearance to prevent an otherwise square-cut big-end bore from interfering with the radiused fillet.

Aluminum Rods

Aluminum rods have their advantages, but they’re not for everyone. Yes, they may be lighter compared to forged steel, but they’re more expensive, and they’re fatter, so clearance concerns become more of an issue.

Aluminum rods start as dense forgings or dense-forged billet stock that are CNC machined to the final shape. Materials are commonly a 7075 or 7075-T6 aluminum alloy. Die-forging provides a more highly dense grain structure for added strength. During the forging process, the material is exposed to about 700°F and impacted with as much as 2,200 tons of pressure, resulting in enhanced grain flow and material density.

While weight reduction is a plus, due to the increased thickness, more attention is required in terms of clearance checking. If aluminum rods are used, just as hard washers are needed for aluminum cylinder head bolt locations, hardened washers must be installed under the rod bolt heads to prevent the bolt heads from digging into the parent aluminum. Aluminum rods are ideal for extremely high RPM and are suited for drag racing because the aluminum flexes and serves to absorb compressive and transitional energy to/from TDC.

Drag engines are run hard and then shut off at the end of the run. However, that characteristic makes them unsuitable for road racing applications where the flexing under loads is continuous. A myth is that aluminum rods stretch too much. They actually don’t stretch. The material expands more compared to steel. In terms of length growth, the rod may only grow under operating temperature by only a few thousandths of an inch. Obviously, piston-to-valve clearance must be more tightly adhered to.

Aluminum rods typically feature an I-beam design for clearance reasons. Since an aluminum rod beam must be wider to begin with, an H-beam design would make the beams even wider. One downside of aluminum rods, aside from the higher price, is cycle life. Because the material grows and flexes, the fatigue life is shorter compared to steel, so the frequency needed to replace them in terms of the number of races/runs is greater.

Billet Rods

Billet rods begin life as dense-grain forged plate stock that is then CNC machined to shape. Billet rods are available in both alloy steel and aluminum materials. The cost of billet rods is higher in comparison, simply due to the material wasted during machining from a blank and the increased labor/ machine time involved. Billet rods also offer another advantage: since the rod is machined from a blank, custom rod dimensions are possible for those who are developing their own platforms and feel the need to experiment with specific length, width and beam shapes for those rare instances where available in-stock rods don’t meet custom requirements. However, you’re going to pay for that privilege in terms of CNC programming and machining time.

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Aluminum is obviously lighter than steel, but aluminum rods need to feature a larger cross section to provide enough beefiness/ strength. Aluminum rods are CNC machined from dense billet forgings and offer a very tight grain pattern. The example seen here is from GRP.

How to Build Horsepower with a Small-Block Chevy: Connecting Rods - Chevy DIY (11)

Rather than relying on the dowel sleeve and/or rod bolts to register the cap to the rod saddle on this GRP aluminum rod, radius-pattern tooth grooves have been machined into both mating surfaces for an extremely precise cap register.

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Because aluminum rod material expands more than steel, the rod’s big end diameter tends to slightly grow under temperature, reducing rod bearing crush. To stabilize the lower rod bearing, an aluminum rod cap will feature a small locating dowel that engages a hole in the lower rod bearing. This prevents the rod bearings from potentially rotating in the big-end bore. It is not recommended to run tighter rod bearing oil clearance in an attempt to compensate, which can be detrimental to cold engine conditions. If the builder notes a slight drop in oil pressure, the preferred choice is to run a higher viscosity oil

Titanium Rods

As with most choices of materials and design, there are advantages and disadvantages. The highlight of titanium involves its lighter weight compared to a steel or aluminum rod of the same size and its strength-to-weight ratio. Typically, a titanium rod is machined from Ti6AL4V stock, which is approximately 33 percent lighter than a comparable-sized forged steel rod. This reduces the reciprocating weight, an obvious advantage in terms of accommodating high engine speeds and in attaining quicker RPMs.

The disadvantages involve higher cost and the need for increased care and attention in terms of nicks or scratches because the material, while offering high tensile strength, is very susceptible to failure from stress risers. Titanium is also rather gummy when exposed to contact friction and can easily gall. The potential concern is at the sides of the big ends if/when they contact each other. To address this, the titanium rod’s big-end sides may be either highly polished or treated to a hard-surface coating.

How to Build Horsepower with a Small-Block Chevy: Connecting Rods - Chevy DIY (13)This Tech Tip is From the Full Book, HOW TO BUILD KILLER CHEVY SMALL-BLOCK ENGINES. For a comprehensive guide on this entire subject you can visit this link:


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Connecting Rod Length

Published rod length refers to the distance from the center of the small-end bore to the center of the big-end bore, referred to as center-to-center length. Performance rods for small-block Chevy applications are commonly available in inch lengths of 5.700, 5.850, 6.000, 6.125, 6.200, and 6.250 to suit various combinations of the crank stroke, piston compression height, and block deck height.

As mentioned earlier, the combination of half of the crank stroke, rod length, and piston compression distance (CD) must add up to meet the desired piston do me location relative to the block deck surface.

For example, if your block deck height is 9.025 inches, and you want to achieve a zero-deck (where the piston dome is flush with the block deck), the combination of half crank stroke, rod length, and piston CD must stack up to meet that 9.025-inch dimension.

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Titanium rods are available and popular due to their light weight. However, they are substantially more expensive and are much more sensitive to scratches or dings that can result in stress risers, so great care is required when handling. Shown here is an H-beam titanium rod by GRP.

Rod to Block Clearance

Regardless of your setup, clearance of the rod’s big end to the block pan rail and cylinder bottom should always be checked during engine mockup, regardless of the stroke being used. Obviously, as you increase the stroke (or when using fat aluminum rods), the rod’s big ends, usually at the rod bolt locations, are going to get closer to these block areas, so it’s critical to verify clearances to determine if clearance reliefs are needed at the block.

With the crank installed on its bearings, mock install the piston/rod with the rod bearings in place. There’s no need to fully torque the rod bolts at this point. Just snug them to make the cap flush to the rod saddle and slowly rotate the crank, observing the clearances. If the clearance is too tight, mark the block interference locations with a marker. Do this with each rod location. With all the components removed back to a bare block, carefully grind material to obtain clearance. Clean the block and repeat the test assembly, again verifying clearances. As a general rule, at least a 0.080-inch clearance should be at all rod-to-block locations.

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A rod’s big end and the camshaft tunnel are visible. When the crankshaft stroke is increased and cam lobe lift is increased, closer attention to the clearance of the rod’s big end to the camshaft is needed. This is why aftermarket block makers offer raised-cam blocks to move the cam farther away from the rods.

Potential rod big end to camshaft clearance concerns arise when the stroke is increased, when large aluminum rods are used, and/or when a camshaft features a larger base circle. This is why aftermarket blocks are available with raised cam tunnels to move the cam away from possible rod strikes.

Rod Side Clearance

Rod side clearance is important. If it’s too tight, the pair of rods on a common journal will rub against each other, creating friction, potential galling, and excess heat. If it’s too loose, the rods can slide excessively fore/aft, which can place undue loads on the rod bearings and at the piston pin area, which can adversely affect piston skirt side loading at the cylinder walls.

During test fitting, use your fingers to spread the two rod big ends on a common journal apart against the journal fillets. Insert a clean feeler gauge between the rod sides. A generally recommended clearance is in the range of 0.014 inch. I would say 0.012 inch is the minimum, and 0.019 to 0.020 inch is the maximum.

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Due to a higher degree of precision machining, high-quality aftermarket rod big end widths tend to provide proper and more consistent side play clearance. When coupled to a high-quality aftermarket crank where journal width is held to close and consistent tolerance, it’s rare for the rod’s big end width to require correction. Today’s quality aftermarket cranks and rods simply provide better finished machining.

Beam Design

The rod beam (the area of the rod that connects the piston wrist pin bore to the big-end bore) must provide the strength, in terms of compressive and tensile forces, to withstand the forces induced during high-RPM and high-torque abuse. Common beam designs include the I-beam and H-beam.

The I-beam features a slimmer face width compared to an H-beam and has a groove relief running along the face of each side of the beam. Face refers to the sides of the beam that align with the flat side of the big end. If you cut an I-beam rod at the midpoint of the beam, the cut surface would mimic an uppercase letter I. An H-beam rod features the relief groove on each side of the beam in line with the rod bolt sides of the big end. If you cut the beam, the cross-sectional view would look like the uppercase letter H.

What’s the difference? Assuming the rod was made by an established quality-minded aftermarket manufacturer, either design will provide the desired performance and durability. However, when choosing between the two designs, an I-beam style rod is theoretically better suited for high-RPM use due to its generally lighter weight compared to an H-beam rod, assuming both are made of the same steel alloy material. An H-beam rod is theoretically better suited to handle high-torque engines.

In theory, H-beam rods are stronger, but in reality, an H-beam rod can be lighter while being as strong as an I-beam rod. In many cases, choosing between I-beam and H-beam boils down to either manufacturer availability and/or the engine builder’s preference.

A beam style developed more recently is the X-beam. The X-beam design represents a hybrid approach using a combination of I-beam and H-beam with weight-saving grooves on both the beam faces and sides. This is often available on bulkier aluminum rods to provide both a level of weight reduction and an increase of surface area for enhanced strength.

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I-beam rods tend to be a bit lighter than H-beam rods and are good choices where high engine RPM is a concern as opposed to high torque. H-beam rods may offer a bit more strength and rigidity and may be better at handling higher compressive forces where the engine produces lots of torque. (Photo Courtesy Oliver Racing Parts)

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The aftermarket connecting rods available today far surpass OEM rods in terms of materials, designs, construction, precision machining, closely held tolerances, accommodation of increased strokes, weight-matching sets, strength, and a broad range of lengths and big-end diameters. An example of a Scat forged steel H-beam rod is shown here.

Rod and Cap Numbering

It should be obvious that rods and their caps must always remain as a matched pair. When the rod is initially assembled to the cap, the big-end bore is final machined. If the cap was installed to a different rod, it would not register accurately, resulting in and out of round bore, unless the assembly was resized and honed. Never mix rods and caps. Again, the need to keep respective rods and caps together is critical.

In the old days when dealing with OEM rods, it may have been necessary to stamp a number, or a series of dots, into the side of the big end’s saddle and cap to provide a reference. Today’s aftermarket performance rods are typically laser-etched with an identical multi-numeral/letter code, at each side of the rod saddle and cap mating line, eliminating the need to perform this on your own. Also, laser etching is non-destructive, applying no pressure to the metal. Using a stamp and a hammer in unskilled hands can potentially distort the big end.

How to Build Horsepower with a Small-Block Chevy: Connecting Rods - Chevy DIY (19)

In the old days, engine builders needed to mark the rod and cap with an identifying mark or number to avoid accidentally mixing caps and rods. Today’s aftermarket rods arrive pre-marked with laser-etched numbers. Since no pressure is used, laser etching avoids potential distortion as opposed to using a number or letter stamp hammered into the surface.

Rod Bolt Tips

The fit and tensile strength of the rod bolts is absolutely critical, especially for high-performance applications. While it was standard practice to upgrade OEM rods with high-quality rod bolts, such as those offered by ARP as an example, aftermarket performance rods are always assembled and shipped with high-quality/ high-strength rod bolts from the get-go. These high-performance rod bolts typically feature a 12-point head design. The 12-point design provides a more secure engagement and is naturally driven by a 12-point wrench. This design also allows the use of a smaller-diameter head, which provides easier access due to the smaller outer diameter of the appropriate-sized socket wrench.

High-performance rod bolts designed for racing applications are also available in a variety of thread diameters. Shank lengths and material formulation affect the recommended installation torque and maximum allowable bolt stretch.

Thread diameter and length are specific to the design requirements of the rod itself. A numeric code is commonly featured on the bolt head that indicates the type of material. Typical materials are 8740 or 2000. The 8740 rod bolts are chrome-moly, offering a tensile strength of 180,000 to 210,000 psi that is adequate for most racing applications; 2000 rod bolts differ in alloy formulation and can provide higher clamping loads of as much as 220,000 psi.

A set of aftermarket rods includes a spec sheet that provides the recommended torque value and the “do not to exceed” amount of bolt stretch based on thread diameter, shank length, and the type of material. For example, a set of Scat connecting rods equipped with ARP rod bolts includes a spec sheet that lists the torque and max stretch for 5/16 x 1.500-inch ARP 2000, 3/8 x 1.600-inch ARP 8740, 3/8 x 1.600-inch ARP 2000, 7/16 x 1.400-inch ARP 8740, 7/16 x 1.500-inch SCAT 2001, 7/16 x 1.600-inch ARP 8740, 7/16 x 1.600-inch ARP 2000, 7/16 x 1.800-inch ARP 8740, and 7/16 x 1.800-inch SCAT 2001 cap screws. Each one is listed with its own recommended torque value and the amount of bolt stretch that is not to be exceeded. Simply measure and identify your rod bolt thread diameter, bolt length, and type of material to determine the proper tightening value.

Because the popular method of rod bolt installation involves monitoring the installed bolt stretch/ degree of elasticity, performance rod bolts typically feature a dimple at each end to provide engagement points for the use of a rod bolt stretch gauge.

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When installing rod bolts, pay attention to the bolt diameter, length, and material series because the torque value and/or maximum allowable bolt stretch will differ. For example, a 7/16 x 1.6-inch 8740 rod bolt may be specified for 63 ft-lbs with ARP lube and max stretch of 0.0050 inch, while a 7/16 x 1.4-inch 8740 bolt may call for 64 ft-lbs and a max stretch of 0.0046 inch

Tightening Rod Bolts by Monitoring Stretch

While I dislike referring to the old days when it comes to addressing the topic of tightening connecting rod bolts, rather than applying a specified torque value alone, monitoring the amount of bolt stretch provides distinct advantages of not only achieving a more accurate degree of clamping force but also is a way to monitor and maintain records of each bolt’s condition. A bolt, such as one used in a high-tensile application of connecting rod applications, can be viewed as an elastic component. When exposed to a specific amount of clamping force, the bolt slightly stretches, or elongates, displaying a degree of rubber band elasticity. If under-tightened, insufficient clamping force between the rod saddle and cap won’t be achieved, potentially allowing the cap to slightly pull away from the saddle, reducing rod bearing crush. If over-tightened, the bolt may be pulled beyond the elastic state where the rubber band effect is lost, in which case the bolt becomes weakened with resulting bearing looseness and potential rod bolt failure.

As noted, checking and monitoring rod bolt stretch provides a more accurate achievement of clamping force because this eliminates the potential frictional factor that is experienced when relying on the applied torque value alone. By staying within the specified stretch, we are measuring and recording the actual elastic range of the bolt. This is extremely useful when engines are repeatedly rebuilt and/or inspected between races. By recording each individual rod bolt’s location in terms of initially installed stretch, we can recheck to see how far the bolt stretches under a given torque value. For example, if a bolt initially stretched by 0.0045 inch when torqued to 70 ft-lbs, but now that same bolt stretches 0.006 inch at the same torque value, we can determine that the bolt is no longer within spec and must be replaced.

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While only a torque specification was followed in years past, as part of the effort to enhance and evolve, the most precise method of securing rod bolts is to monitor rod bolt stretch. The suggested torque value can be used as a baseline, but measuring bolt stretch provides a much more accurate method of achieving and determining bolt clamping load. Each bolt is first indexed on a stretch gauge in its relaxed state with the gauge set at zero.

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While it’s always been common practice to lubricate rod bolts, today’s high-tensile-strength rod bolts offered by firms, such as ARP, are to be coated with a high-pressure and friction-reducing lube, such as ARP Ultra-Torque lube or CMD. Lube must be applied both to the threads and the underside of the bolt head. The use of specific lubricants, as opposed to engine oil, can significantly affect the frictional level during tightening. Pay close attention to the rod maker’s and/or rod bolt maker’s torque values with regard to the type of lube being used. If you follow the torque value specified for 30W oil but have applied a reduced-friction lube, you can overstress the bolt by overtightening. As an arbitrary example, if the spec for a given rod bolt is 65 ft-lbs for ARP lube and 75 ft-lbs for oil, if you tighten to the higher oil spec when using ARP lube or CMD, you risk tightening the bolt beyond its max stretch spec. The specialty lubes provide reduced friction, requiring less applied torque compared to the use of engine oil.

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Once the bolt is tightened, the same gauge is placed onto the bolt to see how far it has stretched. The rod bolt and/or rod maker will provide a specification list on the recommended and maximum-allowable bolt stretch. The gauge is zeroed for each bolt before bolt installation. Rod bolt stretch gauges have become a mainstay tool for engine builders. Simply put, monitoring bolt stretch eliminates guesswork and not only helps obtain more precise installation but can also be used to determine if a used rod bolt no longer provides its needed elastic properties.

Rod bolt stretch gauges are offered by several sources, such as ARP, Goodson Tools & Supplies, Moroso Performance Products, and others. The gauge features a dial indicator, a fixed pointed anvil, and an opposing spring-loaded adjustable centering probe. The pointed ends engage to the rod bolt at the bolt’s head and shank tip dimples. Before installing the rod bolt, place it in the gauge, applying a small preload. Adjust the gauge to read zero. This provides a static free-length of the bolt.

Remove the bolt from the gauge, lube it, and install it to the rod. Do not change the current needle setting on the dial indicator. If the specified torque value for that application calls for 70 ft-lbs, using a torque wrench, tighten the bolt to 70 ft-lbs. Then, install the stretch gauge. Since you zeroed the gauge at the bolt’s free length, the gauge will now show how far the bolt has stretched at your torque value. For example, if the rod maker’s spec sheet lists a stretch not to exceed 0.0062 inch, and your stretch reading shows 0.006 inch, you know that you are within the allowable range. The engine builder may prefer to begin by torquing the bolt to 50 ft-lbs, then 60 ft-lbs, etc., checking stretch after each torque application to provide a picture of how much stretch is occurring as increased torque is applied.

Note that the stretch gauge must be individually zeroed for each bolt because individual bolt lengths and dimple depths can vary. In other words, do not assume that by zeroing the gauge for one bolt, that the remaining bolts will zero at the same point on the gauge. Treat each bolt as a unique part.

REM Finishing

REM finishing has become increasingly popular for applications, including crankshafts, connecting rods, camshafts, and more. This is essentially a chemical and tumble-polishing process that smooths out the surface finish to an almost chrome-plated appearance. The advantages include micropolishing to reduce or eliminate microscopic machining peaks and valleys. This results in a more uniform and uninterrupted surface and softens any sharp edges, which eliminates potential stress risers.

The ultra-slick finish also helps to shed parasitic oil cling, potentially freeing up power due to reduced drag. REM finishing services are available from some rod makers as an option, as well as independent metal finishing services across the country. Costs vary, but typically this process for a crank and a full set of rods may run in the range of $500 to $600.

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This closeup of the REM finished rod cap gives you a better view regarding the surface finish, taking on the appearance of a highly polished or chrome-plated finish.

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This is an example of a rod that has been treated to an REM finish process. This chemical and tumble-polished process results in an extremely smooth surface, eliminating microscopic peaks and valleys in the surface finish. This makes the rod stronger and less susceptible to fatigue, and it provides a slick surface to reduce parasitic oil cling, reducing windage drag.

Written by Mike Mavrigian and republished with permission of CarTech Inc


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If you liked this article you will love the full book!



Does connecting rods increase horsepower? ›

In an overhead cam four or six cylinder engine, the rods may be designed to handle up to 7,000 rpm but probably only about 200 to 250 horsepower. As a rule, most stock connecting rods can handle up to 25 to 40 percent more horsepower than an unmodified engine was originally designed to produce.

What is stronger H-beam or I-beam connecting rods? ›

H-beam is a stronger design when bending stress is considered,” Davis said. “H-beam rods are more difficult to machine, so they are often more expensive. I-beam rods are easier to produce and can sometimes be lighter than H-beams. All other variables being equal, H-beam rods are the strongest design.”

What is the rod ratio on a small block Chevy? ›

Divide rod length by the crank stroke and you get the rod ratio. For example, say you're building a stock small block 350 Chevy with 5.7-inch rods and a 3.48 inch stroke. The rod ratio in this engine would be 5.7 (rod length) divided by 3.48 (stroke), which equals 1.64.

What is the best connecting rod for boost? ›

If you're trying to make a lot of boost, an I-beam connecting rod is the best choice. When you need to lighten up the rotating assembly the H-beam connecting rod should be at the top of your list. These rods are a better fit for a naturally-aspirated engine where you're turning a high level of rpm.


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Hobby: Genealogy, Stone skipping, Skydiving, Nordic skating, Couponing, Coloring, Gardening

Introduction: My name is Ms. Lucile Johns, I am a successful, friendly, friendly, homely, adventurous, handsome, delightful person who loves writing and wants to share my knowledge and understanding with you.