understanding and selecting connecting rods€¦ · line on both the rod and cap (pm rods are often...

28 APRIL-JUNE 2014 engine professional

TYPES OF RODSConnecting rods are available in a wideselection of design and materials. Whilemany early rods were made of cast iron,this style should never be considered forany performance build. Today’s materialchoices include powdered metal, forgedsteel, aluminum and titanium. The twobasic “style” choices include I-beam andH-beam, which we’ll discuss here.

ROD BEAM DESIGNThe three beam designs include I-beam, H-beam and X-beam construction, with Iand H styles being the most common. Theterms refer to the shape of the rod beam’scross section. If you cut an I-beam rod atthe center of the beam, the cross sectionresembles the capital letter “I.” If you cutan H-beam rod, the cross section lookslike the letter “H.” An I-beam rod featuressmooth sides, with a big groove runningthe length of the front and rear beamfaces. An H-beam rod features flat,smooth faces, with grooves on each side ofthe beam. A more “exotic” and lesscommon style is the X-beam rod whichfeatures grooves on faces and sides (forweight reduction while retaining strength).

How do you choose between I-beamand H-beam rods? All other variablesbeing equal, I-beam rods tend to be a bitlighter than H-beam rods, and areperfectly adequate for mild to wild streetengines. Depending on the rod

manufacturer’sratings for aspecific rod lengthand engineapplication, I-beamrods can handleupwards of 500 to 700HP. H-beam rods tend tobe slightly heavier, butoffer increased rigidity forhigher RPM and torqueapplications, since this design is moreresilient against higher compressive forces.For mild to wild street powerplants, eitherstyle is acceptable. As more stress isimposed (higher compression ratio, forcedinduction, etc.), a move to H-beam makessense. We could also consider factors suchas windage and parasitic oil cling, but thenwe’re getting into serious racingapplications where every ounce of powercan be a game changer.

PM RODSThe vast majority of current OEconnecting rods are of the powdered-metal(PM) type. For example, all of the factoryGM LS-platform engines feature PM rods,with the exception of the LS7 and LS9,which feature forged titanium rods.

Powdered metal rods are “pressurecast,” with a specially-formulated metalpowder that’s placed into a mold, thenheated to a melting point and pressurized.Once out of the mold, the small and bigends are honed to size and rod boltthreads are cut. The rod is then secured ina fixture at the parting line area, and thecap is then snapped off, with no loss ofmaterial. The result is a fractured partingline on both the rod and cap (PM rods areoften referred to as “cracked cap” rods).While this process may at first seem a bitcrude, it creates a very precise matingsurface interlock. The cap fits to the rodprecisely (mirror image surfaces) forperfect cap-to-rod alignment. Because of

Understanding and Selecting

Connecting Rods

BY MIKE MAVRIGIAN

H-beam rods feature flatbeam faces with a weight-relief/strengthening grooveon the sides of the beam.

EPQ214 28-39_Layout 1 4/12/14 7:16 AM Page 28

www.engineprofessional.com 29

this mating design, each cap must alwaysremain with its original rod. While a PMrod big-end bore can be slightly oversizehoned and mated with oversize-O.D.bearings, these rods cannot be re-sized inthe traditional manner (where matingsurfaces are ground flat to create a smaller,non-round bore, and then honed roundagain). Care must be taken when handlingPM rods so as not to damage the irregularmating surfaces.

PM rods are surprisingly strong andperfectly acceptable for street use, but ifyour build is destined to spit out overabout 400 HP, I’d recommended anupgrade to stronger rods (forged steelbeing the most common upgrade). If youdo plan to retain original equipment PMrods, I strongly suggest eliminating the OErod bolts in favor of much strongerperformance rod bolts, such as those madeby ARP.

OE PM rods, while satisfactory formost street applications, have theirlimitations in terms of horsepower-relatedstress, there are a few performanceaftermarket PM rods that are nowavailable that feature a much moresophisticated metal alloy mix that iscooked and pressurized to higher levels,that are reportedly capable of handlingupwards of 800+ horsepower (sort of ahybrid approach of both PM technologyand forging). I’ve not had a chance to usethese new PM rods yet, but what I’ve

heard so far has been very positive.While PM rods have traditionally been

used only at the OE level, we’re now alsostarting to see high performanceaftermarket PM rods. Howards Cams, asan example, teamed up with GKN andnow offers forged powder metal rodtechnology with an extremely dense andnon-directional grain structure. A high-tech base powder is blended with selectalloy elements. Melting, atomizing andannealing are controlled to exactingstandards. The metal-mix is compacted (indies) under tremendous pressure, at over1500 degrees F. Hot forging with a 750-ton press finalizes the structure of themetal. This new generation of PM rodsrepresents a hybrid of both PM andforging.

While OEM-level PM rods are (asstated earlier) good for around the 400 HParea, and maybe even a max of 500 HP(although that’s pushing it). Howard’snew PM rods represent a new level in OMtechnology, and even with 5/16” ARP2000 rod bolts, their rods are rated for585 + HP. Reportedly, when fitted withL19 rod bolts, these rods have evensurvived at 800 + HP levels.

WHY THE OEs ARE USING THESE RODSThe OEs are using powder forgings for anumber of reasons. Tighter tolerances canbe maintained in both dimension andweight, and the use of a powder forging

process makes connecting rods which areeasier to machine, require less stockmaterial, and the process eliminates asmany as six machining operations.According to MascoTech, a primarymanufacturer of these rods for the OEs,the increased machinability of powderforging has reduced tooling per unit costfrom about $0.22 to about $0.04.

DESIGN ADVANTAGES OF POWDER METAL FORGING• Even distribution of stress over theentire side of the I-beam area.

• Increased I-beam rigidity (100%increase in stiffness over conventionalforged).

• Improved noise/vibration/harshnesslevel, which improves piston and ringaction.

• No bore offset between rod and cap.• Increased bore stiffness and geometry.• Increased bearing reliability.• Reduced weight.• Crankshaft mass reduction.• Single weight grade (+- 2g on 400g rod).• Reduced mass variation for improvedbalance.

• Full density across entire rod.• Lower cost carbon steel.• Proven fracture split method (no crankbore elongation during cracking)

• High machinability.

(continued)

The deep groove on the beam sides of an H-beam rod reduce weight andprovide extra rigidity for higher horsepower and torque and higher-RPMapplications, as compared to I-beam rods.

I-beam rods feature smooth beam sides and face recesses. I-beam rods aretypically lighter than H-beam designs. Depending on material, length andapplication, forged steel I-beam rods are generally viable for 500-700 HPapplications.

EPQ214 28-39_Layout 1 4/12/14 7:16 AM 9

RECONDITIONING PM RODSA major concern when trying torecondition cracked cap rods in thetraditional manner relates to the irregularmating surfaces of the rod and cap. Whenthese rods are manufactured, they areformed as a single piece. The caps are thenseparated by fracturing the cap from therod, which leaves an irregular (and unique)mating surface. This irregular surfaceprovides an accurate locating of the cap tothe rod, preventing any misalignment ofthe cap during assembly.

However, if the mating surfaces aremachined or ground flat, in order toreduce the rod's large end bore inpreparation of re-honing to size, you loseall centering ability. As described earlier,this would destroy the unique cap-to-rodinterlock that was created when the capwas broken away from the rest of the rodduring manufacturing. Since no interlockmating remains, and since there are nopositioning tangs to use, this makes itpossible to install the cap slightly off-center, due to the small tolerance range ofthe bolts to the cap's bolt holes. As aresult, the cap might then be installed off-center left-to-right (laterally), or at anangle relative to the axis of the large endbore. If only for this reason, it is notadvisable to reface the rod and cap matingsurfaces.

The other reason that an attempt toresize these rods can create a problem isdue to the relatively thin cap material.Once the mating surfaces are ground flat,the new smaller and non-round large endbore may require so much enlargement inorder to create a round hole that the capmaterial may be reduced enough to createa potential weak area. We need to notethat in the process of creating flat matingsurfaces, it may be necessary to reduce themating surfaces by as much as .040" ormore, which could result in a combinedreduction of the hole by as much as .080"or more. Precious little cap material maybe left after resizing in this instance.

The best approach, if resizing isnecessary, is to avoid disturbing theirregular cracked mating surfacesaltogether. Instead, hone the big end to anoversize that will accommodate the fittingof oversized-O.D. rod bearings.Unfortunately, these oversized bearings arenot yet available for all cracked capapplications, so check with your bearingsuppliers before committing to this. Ifavailable though, bearings may beobtained that feature a standard size I.D.

and a .002 + .003" larger O.D.; or in anundersized I.D. (to accommodate anundersized ground crank) and an oversizedO.D. to accommodate an enlargedconnecting rod big end.

FORGED STEEL RODSForged steel rods are constructed startingwith an ingot of steel alloy, generally using5140 or the stronger 4340 chrome molysteel. The steel is heated and hammer-forged under enormous pressure of around240,000 lbs at around 2200 degrees F.This produces a tight internal grainstructure wherein the molecules are moretightly compacted. This is followed byheat-treat hardening, final machining andstress relieving. On some early OE forgedrods, you may notice what first appears asa “casting mold seam,” which is simply a

trace of the outer edge that remained afterthe initial forging was stamp-trimmed toremove any excess material that squeezedout of the stamping pattern. Today’saftermarket performance forged steel rodsrarely feature this, as forging techniquesand finish machining have become muchmore advanced.

Individual manufacturers often employtheir own proprietary formulas, butgenerally speaking, during conventionalsteel forging, a steel ingot is heated in anoven to about 2,200 degrees F (at whichpoint the steel very formable…not yet aliquid, but very easy to move around andshape). The ingot is then placed in aforging die and squeezed into theapproximate shape of the desired profile.This “squeezing” is performed either by ahammering or pressing process. Either


CONNECTING RODSBY MIKE MAVRIGIAN

Powder metalrods arepressure moldedas one piece.The caps arethen separatedby a controlledfracturing or“cracking”process wherethe cap issnapped off ofthe rod. Theresultingirregular matingfaces thenregister backtogether veryprecisely.

The irregularmating surfacesat the partingline is unique toeach rod’smating area.When the rodbolts aretightened tospecification,the parting linedisappears. It’scritical toalways keepeach cap withits original rod.PM rods cannotbe resized in thetraditionalmanner.

EPQ214 28-39_Layout 1 4/12/14 7:16 AM 0


way, the goal is to compress the alloy mixnot only to precisely fill the die, but also toincrease the strength of the alloy bycompacting the molecules and aligning andstrengthening the grain structure. Basically,the size of the ingot is much larger thanthe volume required in the die (generally,this will start with an ingot that weighsabout twice as much as the desired finalproduct). During the forging/compactingprocess, the excess material is forced outof the die at its mating lines. This excess islater sheared off in a trimming die.

The trimmed, rough-shape forging isthen quenched and tempered. Heattreating is best done before machining,since the heat treating/tempering processcan deform the part’s shape by as much as0.060”. Manufacturer methods may vary,but this might involve quenching the partin a glycol solution. The part is thenmachined to its final shape. Oncemachining is completed, the rod is stress

relieved to remove any stresses that mighthave been induced by the machiningprocess. This may be done in an oven,heating the rods to within 400-600 degreesF. Both the heating and cool-down timesare carefully controlled. The rod is thenfinal-machined for small and big-end boresize. The final step involves achieving thedesired surface hardness.

ALUMINUM RODSThe benefit of aluminum rods (whetherforged or cut from extruded billet stock)involves weight reduction. However, eventhough aluminum rods are generallyfabricated using 7075 or 7075-T6aluminum alloy, in order to perform athigh stress levels, aluminum rods arethicker and beefier, requiring moreclearancing with regard to block andcamshaft clearances. Due to the highercost of aluminum rods, it really doesn’tmake sense for a street engine.

BILLET RODSBillet rods, as the term implies, aremachined from dense material blank stock(forged and or extruded). Billet rods, ascompared to forged rods, may be lighter,but are more expensive due to the cost ofthe high-grade stock and the CNCmachining. For even an ultra-strong streetengine, this is slight overkill, unlessbudgeting isn’t a concern.

TITANIUM RODSIf you want the lightest rods with the beststrength-to-weight ratio, titanium is thechoice. However, it’s pricey. Since you’llonly realize the weight benefit from the5,000 rpm and up range, you really don’tneed titanium rods for any street engine.

Titanium rods are billet-machined fromTi6AL4V stock, and are about 33%lighter as compared to a same-applicationforged steel rod. However, titanium rodsare much more expensive. Since you’re

Aluminum connecting rods, although made of high-density aluminum forgings or cut from billet stock, are beefier and command more room. Extra attention toclearances between the rod big end and the block and camshaft is critical.



really only going to see/feel the advantageat engine speeds over around 5,000 rpm orso, it’s really a waste of money for a streetengine. Also, titanium, for all of itsstrength-to-weight features, is a fragilematerial that is sensitive to scratches. Smallscratches in the surface can lead to stresscracks, which leads to rod failure. Also,titanium (from a friction/machiningstandpoint, is rather “gummy” and likes togall when rubbed (in the case ofconnecting rods, this concern exists at therod big-end sides), so titanium rods mustbe polished and/or coated with a hard-surface coating (such as chromium nitride).

WHICH ROD MATERIAL?Forged or billet steel is suited for the vastmajority of street and race applications.Where further weight reduction is desired,forged/billet aluminum rods are available,but at a higher cost. For high-RPMengines where weight savings are reallycritical, titanium rods are an option, butthey tend to fatigue over time, ascompared to steel. When used in racingapplications they will likely need to bereplaced more often, as compared to steelrods. Titanium rods are also veryexpensive, which is a major factor whenyou’re on a real-world budget. Aluminumrods are lighter than steel but cost lessthan titanium and more than steel.Aluminum rods tend to be more on thechunky side and generally require moreattention to block clearance.

CENTER-TO-CENTER LENGTHRod length refers to the distance betweenthe centerlines of the small end (piston pin)bore to the big end (rod pin) bore. Rodlength is a factor in determining thecombination required to achieve a specificstroke, relative to the block deck height.

For example, let’s say that you want toachieve a zero-deck clearance (where thepiston top is flush with the block deck).The crank stroke, rod length and pistonCD (compression distance) all stack up tocompare to the block deck height.

• The block deck height is the distancefrom the crank main bore centerline to theblock’s cylinder head deck.

• When considering stroke, we onlyneed to factor half of the crank’s totalstroke, since we need to consider thedistance from the centerline of the crank’srod journal at top-dead-center position. Ifyour crank has a 4.00” stroke, we onlyneed to factor-in half of total stroke, whichin this example is 2.00”.

• Piston CD is measured from thecenterline of the piston’s pin bore to the


Some high-dollar racingaluminum rodsfeature veryprecise capmating surfacessuch as thebroach cutsseen here.

The radiusgroove broachcuts register thecaps to the rodswith extremelyhigh precision,eliminating anychance for thecap to move inrelation to therod.

Connecting rod length alwaysrefers to the distance from thecenterline of the small endbore to the centerline of thebig end bore. (Illustrationcourtesy Lunati.)



top deck of the piston.If you know the block deck height and the crank stroke,

you can choose the combination of rod length and pistonCD that will place the piston deck at the block’s deck (or todetermine where the piston will be at TDC relative to theblock deck).

EXAMPLE: If the block deck height is 9.980” and youplan to use a 4.150” stroke crank, a 6.760” rod and apiston CD of 1.113”, the top of the piston will be 0.032”below deck. If you want the piston flush with the blockdeck, the piston CD would need to be 0.032” higher, or1.145”.

If you desire that the piston is flush with the block deck:BLOCK DECK HEIGHT = ½ stroke + rod length + piston CD

One half of the crank stroke, length of the rod and thepiston’s compression distance are added together andcompared to the block’s deck height.

ROD CLEARANCESThere are six basic areas to consider relative to connectingrod clearance to other components:

• Big end of the rod to the block (when stroke isincreased, check clearance at the pan rails and at the bottomof the cylinders). With main bearings, crank, rod bearings,rods and pistons test-installed, slowly rotate the crank andobserve how close rod big ends are to the lower areas of theblock. A minimum of about 0.080” is recommended.

• Big end of the rod to the camshaft (when usingincreased stroke). About 0.070” clearance is the minimum.With the cam and timing system installed, slowly rotate thecrank and observe clearance at all rod big end areas.

• Small end of the rod to the underside of the piston(only a concern if using rods that have weight pads at thesmall end). Minimum is about 0.060”.

• Small end of the rod between the piston pin bosses.Minimum is about 0.080”. Especially if using thickaluminum rods, checking this is more critical.

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Today’s high performance aftermarket connecting rods are made withvery high standards and close tolerances. Typically, a set from a leadingmanufacturer will be less than 2 grams in terms of weight variation.Typically there is no need to machine these rods for weight matchingprior to crank balancing.

(continued)




• Rod bearing clearance (this will likelybe in the 0.0025 to 0.0035” range, butalways refer to your engine’s specs. Beaware that forced induction applicationsmay require greater bearing clearance asopposed to naturally-aspiratedapplications)

• Rod side clearance. This is theclearance between the big ends of a pair ofrods on a common journal. With rods andbearings installed, spread the rod big endsapart and insert a feeler gauge between thebig ends. Clearance for steel rods shouldbe in the 0.014 – 0.020” range. Aluminumrods may require slightly greater clearance(refer to the rod maker’s specs)

• Small end of the rod bushing(assuming you’re using floating pins) tothe wrist pins and piston pin bores. Referto the rod and piston makers’ specs.

A note regarding rod to cam clearance:If clearance is required, you have twochoices: remove material from the rod orchange to a camshaft that features asmaller base circle. If you swap out to asmaller base circle cam, you’ll need longerpushrods. Considering today’s CNC

A rod bolt stretch gauge allows youto monitor each rod bolt’s lengthfrom free-state to fully tensioned.With the rod bolt placed onto thegauge, the dial gauge is zeroed toestablish a reference point…




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capabilities, most cam makers can produce whatever youneed, in anywhere from a week to a month, depending ontheir workload.

If you decide to relieve the rods, do this carefully at theupper big end shoulder to avoid weakening the rod boltfemale threaded areas. Also, the grinding needs to be free ofsharp edges and grind/scratch marks. Once the rod shoulderhas been relieved, re-assemble and re-check the clearance.Once you’re satisfied with clearance, carefully polish toremove any potential stress risers. Many of today’sperformance rods are designed with radiused/slopedshoulders to address increased stroke issues, but nonetheless,you should always check for clearance, especially when usingan increased-stroke crank. BE AWARE: If any material isremoved from the rods, this must be done prior to crankbalancing!

NUMBERING YOUR RODS AND CAPSDuring initial assembly and during disassembly, it’s critical tokeep each rod organized with its original cap due toalignment and bearing clearance concerns. Each rod and capshould be identified (adjacent to the parting line). This mightinvolve numbering by cylinder location, or in the case of

Without disturbing the gauge setting, the gauge is then used to checkthe bolt length during the tightening phase. The rod bolt and/or rodmaker will provide a recommended bolt stretch specification. Thisprovides more precise awareness of the bolt’s elastic state as comparedto using only a torque wrench. If undertightened, the bolt won’t enter itselastic state required for proper clamping force. If overtightened beyondthe bolt’s elastic range, the bolt is weakened and can easily fail. Thestretch method allows you to measure how much stretch has beeninduced.



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quality aftermarket performance rods,matching serial numbers may be laser-etched onto a common side of each rodand cap. If your rods are not number-labeled, be sure to label them prior todisassembly. While an old-schoolcommonly involved the use of a numberpunch, try to avoid this method, since(depending on the type of material andmaterial thickness) this may distort the bigend. A preferable method is to use asimple and inexpensive electric engravingpen.

ROD BOLTSIf you’re running stock OE rods in anyengine that’s going to spit out around 350or more HP, upgrade the rod bolts to hightensile strength performance aftermarketrod bolts. If you purchase qualityperformance aftermarket connecting rods,they’ll commonly already include thesehigher quality bolts.

The critical aspect that you need tounderstand involves the handling of yourrod bolts. PAY ATTENTION to the rodbolt or connecting rod manufacturer’s

Rod bolts must be lubricated according to the rod bolt maker’s instructions. Lubrication will allow moreaccuracy and consistency when tightening. Be aware that a different torque specification will applydepending on the use of engine oil versus a moly lube. Because a moly lube greatly reduces friction, thetorque-tightening spec will be lower as compared to the use of engine oil. It’s critical to follow theproduct’s instructions! When applying any lubricant to rod bolts, lube both the threads as well as the bolt’sunder-head area.







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instructions and specifications for lubricating and tighteningthe rod bolts.

Depending on the specific engine application, thetightening method may involve tightening by torque,tightening by bolt stretch monitoring, or (with some latemodel applications) a torque-plus-angle method. Generallyspeaking, a torque/angle procedure will only apply whenusing OE rod bolts. Most performance aftermarket rod boltand rod makers will provide both a torque specification anda stretch range (giving you a choice of tightening methods).

If you intend to use the torque spec, bolt makers willusually provide two different torque values: one with the useof engine oil as a lubricant and one with the use of a specificmoly lube. Torque value will always be a bit lower withmoly, because moly decreases thread and underhead friction(if you use moly but tighten to the oil spec, you run the riskof over-tightening). The use of moly is preferred, since itgreatly reduces friction and provides a more accurate (andconsistent) torque value. When you lubricate the rod boltprior to installation, be sure to apply lube both on the boltthreads and to the underside of the rod bolt head.

Tightening by monitoring stretch is more time-consumingbut more accurate. This involves using a dedicated rod boltstretch gauge to first obtain a relaxed, free length of the bolt.The dial gage is then set to zero. During initial tightening,the gauge is placed onto the rod bolt to monitor how muchthe bolt is stretched. For instance, if the torque spec is 70 ft-lb, the rod bolt could be initially torqued to, say, 60 ft-lb.Check length with the gauge. Tighten a bit more, re-checkwith the gauge, etc. until the recommended amount ofstretch has been achieved. Note: this must be done with eachbolt (the gauge must be zero’d to each bolt’s free length). Ifyou don’t want to bother with monitoring stretch, simplyfollow the torque spec provided by the rod bolt or rodmaker, and you should be fine for a street application. Thestretch method is simply more precise and is commonly usedby pro race engine builders, but it’s also a good way tocreate a record of rod bolt installation for future reference. Iprefer using two rod bolt stretch gauges, with one dedicatedto each rod on a common journal. This allows me to verifybolt stretch as I tighten both of the rod’s bolts.

Remember that bolts are designed to stretch when theyenter their elastic state (you want this “alive” elastic state inorder to provide sufficient clamping force). However, if therod bolt is overtightened and exceeds its designed elasticstate, the bolt immediately weakens. If a rod bolt has been

Whenever you use a longer stroke crankshaft for a given engine, alwaysperform a test pre-assembly to check for possible clearance issues. Inthis example, the bottom of a cylinder bore was slightly relieved toprovide added clearance between the rod bolt and block.




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stretched beyond its elastic range, it must be replaced.Regardless of which tightening method you choose, it’s a

good idea to take advantage of a stretch gauge (even if youintend to tighten with torque only). Regardless of what typeof rod bolts you have (OE or aftermarket), using a stretchgauge, first measure each rod bolt’s overall free-length (whennew and uninstalled) and record this length. Be sure torecord which rod each bolt will be installed to (cyl. 1, cyl. 2,etc.). During any future engine teardowns (or when theopportunity arises), re-measure each bolt’s free length andcompare it to the original (new) free-length that yourecorded. If the bolt has elongated (stretched) by more than0.0005” (one-half-thousandths), replace the bolt, since it hasbegun to lose its elastic properties. Never just assume that aused rod bolt is still serviceable.

ROD BOLT FRICTION FACTORIf a bolt is tightened by addressing only torque value, youmay not necessarily achieve the desired pre-load due to thevariable of friction. Since we can’t predict the frictional loss,measuring rod bolt stretch provides the most accuratemethod of ensuring that the clamping loads will be bothsufficient for the task and that each pair of rod bolts willachieve EQUAL: loads.

Bolt stretch is generated by a number of factors,including tensile strength and mass, including thelength/diameter of the bolt being stretched. For example, let’sconsider two 3/8” x 1” bolts. One features a 1”long shank,with threads on the full 1” of the shank length. The otherbolt features ¾” of shank length that is full-diameter andsmooth, and only ¼” of thread length at the tip. The boltwith partial thread will stretch less, because the shank areabetween the head and nut engagement area has a thickercross-section. The partial-thread bolt will have a .375”diameter shank, while the all-thread bolt will have only a.324” shank (due to the smaller root diameter inside thethread path).

According to ARP as an example, they calculate stretchnumber for every bolt shank diameter and material grade.

If you service engines on a frequent basis, a dedicated rod vise isessential. A composite-lined vise will prevent nicking damaged to therod, holding the big end securely during either bolt removal or tighteningduring test fittings.



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p: 800-521-2936 f: 800-521-0580silver-seal.com

Silver Seal Products | 19224 Allen Rd. | Trenton, MI 48183

silver seal

KEEP AMERICA WORKING!

PREMIUMHIGH-TEMP

HIGH-TEMP LOW-TEMPDIESEL

MARINE

U.S. PATENT#5,482,000

250°-255°F(121°-124°C)

250°-255°F(121°-124°C)

225°-230°F(107°-110°C)

187°-192°F(86°-89°C)

FRONT

BACK

PERSONALIZEDHEAT TABS AVAILABLE!

HEAT TAB ADHESIVEEXCLUSIVE FORMULA!

MADE IN THE U.S.A.

HIGH-TEMP HEAT TABS

PART # HT1

MELTING POINT 250°-255°F(121°-124°C)

We certify that the material supplied pursuant order issued by you

and numbered as listed above conforms to applicable specifications

or requirements.

“For Complete Protection”

silverseal

Batch# 100612

Geoffrey A. Havens Sr., President

Certification of Center Melt MaterialA MUST for Engine Builders - Large or SmallCourt Cases Won with 100% ResultsDO NOT Risk Your Hard Work Using Off Shore Imitations

MADE IN THE U.S.A.

MADE IN THE U.S.A.

MADE IN THE U.S.A.

MADE IN THE U.S.A.




KEEP AMER P E M M A M AMER M A P A A A M M E R MADE IN THE U.S.A.

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MARINEDIESEL

LOW-TEMPHIGH-TEMP

(121°-124°C)250°-255°F

(107°-110°C)225°-230°F

(86°-89°C)187°-192°F

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Using Off Shore Imitations

MI 48183

800-521-0580

On the spec sheet that is included with every bolt set, themaximum allowable amount of stretch is listed, in additionto a torque value, but the torque value should be used as aguide only. The maker does not want the installer to use atorque value as the final indication of bolt stretch. Rather,the bolts should be individually measured for stretch duringtightening, to assure that each bolt is installed at its optimumelastic clamping load.�

A rod cap splitter tool is another handy device. The big end is placed ona 2-piece anvil. With the rod bolts backed off, as the tool handle isturned, the anvil gently and controllably separates the cap from the rodwithout the need to bang the bolt heads with a hammer and potentiallydropping the rod in the process.

Shown here is a view of a block’s camshaft bore. Notice how close theproximity of the rod bolt shoulder to the cam tunnel. If you’re using ahigh-lift cam, and/or you’re overstroking, and/or using thicker-than-stock rods, always check rod to cam lobe clearance.

Mike Mavrigian has written thousands of technical articles over the past 30 years for a variety of automotive publications. In addition, Mike has written many books for HP Books. Contact him at Birchwood Automotive Group, Creston, OH. Call (330) 435-6347 or e-mail: [email protected]: www.birchwoodautomotive.com


understanding and selecting connecting rods€¦ · line on both the rod and cap (pm rods are often...

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