I checked the end play on the big end of the connecting rods to make sure the crank wasnt separated, and both were less than .029" so within spec. The proper condition of a connecting rod is fairly straightforward: The rod must be straight, center-to-center rod length must meet design specs, the pin bore and big-end bore must be perfectly round, each bore must be sized appropriately for wrist pin and crank rod pin fit and oil clearance and the rod must be free of potential flaws. We also thought it would be a good idea to get a perspective from a crankshaft and connecting rod manufacturer, so we spoke to Tom Lieb, owner of Scat Enterprises. 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With performance or racing pistons, this clearance tends to get much smaller and, in some cases, may have to be checked. However, if the situation presents itself where one or two rod journals fall outside the stock side clearance maximum, this is not necessarily a situation that requires investing in new rods. Then add one-half of the small-end bore diameter, plus one- half of the big-end bore diameter. After removing each wire, turn on the engine and check if the knocking sound still persists. As soon as we broached the subject that connecting rod side clearance established oil flow, he laughed and replied – “Yeah, all those guys are off base. We next tried 0.003-inch bearing clearance since that might have been a clearance early racers would run with 20w50 oil. Check connecting rod side clearance by moving the rod from crank cheek to crank cheek. This computed to an area of 0.040 square inch. The best way to understand this is with the classic garden hose flow example. Ford Forum is a community to discuss all things Ford. In a recent Spinal Tap 11,000-rpm LS story, we outlined the engine built by Ben Strader of EFI University with huge valvetrain design and execution assistance from Billy Godbold at Comp Cams. Then measure the clearance with plastigauge. I am still trying to figure out about porting the head. 0000018097 00000 n Refer to "1.2.5 Installation of Cylinder Head". Install the remaining piston and rod assemblies in the same manner. Out-of-round should not exceed more than .00127 cm (.0005 in.) So to wrap all this up, there’s nothing wrong with using factory rod side clearances. This creates a taper or bell-mouth in the rod big end. Today’s connecting rods strain under 3,000+ HP in racing engines or as few as 50 to 300 HP in a passenger car. All rights reserved. When i take this thing to the machine shop I planned to ask for the typical basic services to check the block, head, rods, and crank. This is the connecting rod journal clearance and must conform to the specifications in Table 1-4. A rod with too much bend will limit oil clearance from one side to the other and possibly lock up at the pin end or at the thrust face on the crankshaft. and then a pry bar to pry on it back and forth. 59 0 obj <> endobj xref 59 50 0000000016 00000 n He also made a great point that journal circumference is another variable in this discussion. u put a strip of it on the bearings then tighten down the rod end caps to torque spec, then loosen and remove the rod caps and check to see how … There is a huge difference in circumference when comparing a big-block 429/460 Ford rod journal at 2.50 inches versus the 1.850-inch journal used on many small-block race engines. A worn or bell-mouthed lifter bore can dump gallons of oil onto the crankshaft. We promise not to use your email address for anything but exclusive updates from the Power Automedia Network. – Tom Lieb, SCAT Crankshafts. The viscosity of oil, the bearing clearance, and the temperature of the oil, along with lifter bore clearance all are far more important players with respect to the amount of oil slinging around inside the crankcase. All rights reserved. 0000001661 00000 n This search for advancement has led to digging into areas previously unexplored, with special attention paid to reducing friction as one path to “free” horsepower. For those who demand we cut right to the chase, the gap between a pair of connecting rods does not control the amount of oil leakage past the connecting rods. We had a poorly resized used rod that had 0.0015-inch taper. Check the … If additional clearance is required, remove material from flywheel at point of contact. This is one reason why thin oil is necessary. h�n����7J�+)I�҃Fېj:�#_5�ƟH%Ef`�I� �>��)SR:!���˶���(���/o��F�W��ev��Aw��,bUڦ>c�ۂ� �P�T�~�N%8�bA�-. This change delivered a 0.011 square-inch on one side of the rod. There are no individual clearances, since the rods are free to float side to side on the crank journal and the pistons wrist pins, you just measure the total side clearance. – Jon Kaase. Lieb knows quite a bit about the subject with over 50 years of experience. 0000003470 00000 n Of these three, the lifters offer the largest area and that’s where much of the oil can escape. What is odd is that no one caught the fact that deglazing the cylinder walls was more likely the reason the oil usage problem disappeared. This allows the engine builder to use narrower connecting rods and bearings. H��TMo�F��W��X���~��*i� u��@����R�LR�_�yK�q?�� -���pfރ�2E-e�X�kE���9i�E�9�����4�L�@�W�K���w�gN8�{�F��[�Ng�����@��0��q/.�[�ǻ�䨞H����8 W4�h���t���W�W'�9Y��}��)!�H�2�RS��:� Is this OK? 0000021678 00000 n With that accomplished, we then placed a standard set of rod bearings in a connecting rod and tightened the bolts to the required rod bolt stretch figure ( 0.0055 to 0.0060-inch). h�,‡[�q ࿺�-+���R�I��6E��"���=�����y�h�!��Af�t�0��t���,.�M��g�\>�Gry�y|ш���|�( So always check for taper on rebuilt rods. An accomplished engine builder and technical expert, he will focus on the tech-heavy content that is the foundation of EngineLabs. Where the rods are numbered, this is normally marked on the camshaft side of the assembly . Yet despite this minimal return, this is normal procedure for high-RPM competition engines where every advantage must be maximized. This is caused when the rods are not switched on the mandrel and only honed from one side. He also said that regarding rod and bearing width, it’s critical to maintain a given width to prevent side loading from “corkscrewing” the piston down the cylinder which could edge-load the bearings. Bearing clearance depends on the engine and the intended use. 0000018383 00000 n Both sides combined would equal only 0.022 square-inch of area, which is still roughly half the area of a tight 0.005-inch rod side clearance of area. Piston-guided rods employ a very tight span between the pin bosses, which only allows minimal lateral movement of the piston. Subtract the crank spec from the journal spec, and then subtract the bearing spec from that result. ... Of course you can check his work with a micrometer. As the crankshaft turns, the rod also turns, forcing the piston up and down. No one would offer a guess as to what all this is worth – likely the horsepower numbers for a small-block would be in the low single-digits. or taper not more than .0025 cm (.001 in.) Figure 9-32). The three major points of exit or leakage are the main bearings, the rod bearings, and the area around the lifters. 0000002425 00000 n 6,244 233 1,027. If there is no clearance, check for proper bearing cap installation. The GMC engine which is different but similar calls for.001" to.003" clearance on a new assembly. This reader was merely parroting the widely held belief that rod side-clearance determines the oil flow exiting the connecting rods, and that excessive side clearance cannot be tolerated. The side clearance is seldom an issue on the rods, the real concern is the … 0000068199 00000 n The ends of the rod spin around the crankshaft and the wrist pin of the piston. The connecting rod in a medium speed 4 stroke engine is subject to an inertia whip loading due to the mass of the con rod swinging about the piston pin. 0000005445 00000 n We are not writing this to make these highly-respected engine builders – who have both passed away – look wrong. Install the cylinder head. Airflow and combustion advancements provided power in massive leaps and bounds. 0000004435 00000 n With both bolts stretched, we then place the dial bore gauge to read the vertical oil clearance directly in line with the rod. 1972 Cylinder Head End Bolt Hole Clamp . If the sound is eliminated, this means that the cylinder from where the p… c4է�n{�d_�Y�O�6ۤEHk For maximum accuracy, measure bearing clearance only in the vertical. 0000068736 00000 n A. These three books from three very famous and well-respected race engine builders all state that rod side clearance determines oil flow. The connecting rod is fastened around the crankshaft on one end and to the piston on the other end. In the formative days of race-engine building when men worked in dimly-lit blacksmith shops, horsepower advancements came in great waves. Octane Test Rocker Arm Geometry . 0000011340 00000 n This is a copy of test results published in an old Callies crankshaft catalog. Rather than putting the feeler gauges between the side of the rod and the crank cheek, I always go between the pair of rods. There are other leak paths as well including the oil that is directed to the valvetrain, the area around the distributor on older engines, and performance modifications such as piston oilers that direct oil to the bottom side of the piston and perhaps spring oilers. POLY-LOCK ADJUSTMENT INSTALLED HEIGHT DIMENSION LIFTER BORE BRACE: PONTIAC ROD AND MAIN BEARING CLEARANCES. Lieb also pointed to oil pressure as another variable that contributes to the amount of leakage past the rods. Build your own custom newsletter with the content you love from EngineLabs, directly to your inbox, absolutely FREE! However when i check the small end side to side movement (measurement D in the clymers) im getting .045" on one and almost .050" on the other. The Great Rod Side Clearance Imbroglio: Clearing Up the Confusion Source: www.enginelabs.com Briggs small engine does it matter which way you install the piston connecting rod rod cap on a 24 hp els You can measure rod length by first measuring the bottom of the small- end bore to the top of the big-end bore. Our personal tolerances are .0015 - .0022 on both the … 0000005819 00000 n We’ll also save you the trouble of informing us that Bill Jenkins, Smokey Yunick, and John Lingenfelter have all authored respected engine books that state that rod side-clearance determines oil flow off the connecting rod journals. Loose bearing clearances will increase oil flow while reducing pressure. 0000012331 00000 n This also means the bearing clearance will be quite tight at perhaps 0.0015-inch or less and used with extremely light viscosity oil such as 0w20 or even 0 weight oil. Current clearances are intended to prevent the connecting rods from either being too tight and causing problems as well as to prevent them banging around between the crank cheeks. This flow is also affected by oil temperature, with tighter clearances causing a higher oil temperature. Figure 10 - Checking Connecting Rod Side Clearance CYLINDER BLOCK Check cylinder block for cracks and check inside of cylinder bores for scratches, scoring, pitting, out-of-round and taper. We will safeguard your e-mail and only send content you request. A bad rod or rod bearing will eventually destroy an engine. The next time I have the rods out of my R90 engine I will probably spend the money to have them sized and shot peened after balancing. endstream endobj 69 0 obj <> endobj 70 0 obj <>stream 0000003174 00000 n © 2017 Power Automedia. The crank is a forged one, but I don't know if its … I don't use plasti-gauge for anything, but it does work well for checking the bearing to crank radius, you just put the strip in sideways. 0000008815 00000 n if you want to check rod bearing clearence you need to use plastigauge. All the others have a plain small end. Connecting Rod Side Clearance. (Because of the lower speed of a 2 stroke engine, the whip loading is not large enough to influence the design of the con rod) Added to this, the inertia loads due to the mass of the reciprocating parts cause a stress reversal from high compressive stress … If the connecting rod is overlooked during an engine rebuild, the result is shortened engine life. I don't know what kind of rods they are as I cannot see or feel any kind of identifying marks or castings. 0000011524 00000 n Side clearance means nothing to oil flow. Don't scrape but reverse the cap and check the fit again) Continue this until the entire surface is clean. Video: Remote-Mounted Turbos Tested — What Are You Really Giving Up? 0000002130 00000 n 0000004345 00000 n Suffice it to say, he knows his way around a race engine. What we did was first determine the area of the 0.002-inch of bearing clearance around a 2.200-inch small-block Chevy rod journal and the bearing. When we offered the opinion that rod side-clearance determines oil flow, Kaase was quick to say, “If that’s true, then the whole starting field of a NASCAR race is doing it wrong!” His point is that current Pro Stock, NHRA Competition Eliminator, and NASCAR engine building efforts (among many others) are aimed at reducing friction by using what are called piston-guided rods. Next, we measured the outer diameter of a small-block rod at 2.600-inch and then determined the area of that circumference using an extremely tight 0.005-inch side clearance. 0000001742 00000 n This is a direct quote from the Jenkins book (The Chevrolet Racing Engine) : “We also check side clearance in the normal manner. e~�C,�L���&2���a~!j��H��+�$��q�B2�1͕1c��]��!2�c1�9���3^*g$��e4����!� �m�C#� �C#����f��L@l�Vl�ށ��s A(J� endstream endobj 60 0 obj <> endobj 61 0 obj <> endobj 62 0 obj <>/Shading<>/ColorSpace<>/Font<>/ProcSet[/PDF/Text/ImageC]/Properties<>/ExtGState<>>> endobj 63 0 obj <> endobj 64 0 obj <> endobj 65 0 obj <> endobj 66 0 obj <> endobj 67 0 obj <> endobj 68 0 obj <>stream rod problem solved/ Thanks!!! If you restrict the hose outlet with your thumb, the pressure in the hose increases while the flow volume decreases exiting the hose. As an example, if on a small-block Chevy the side clearance on a pair of rods measures 0.023-inch and the stock Chevrolet spec is 0.008- to 0.013-inch, the additional clearance is not something to stress over. Kaase is perhaps best known currently for his Boss Nine aftermarket version of the original Ford Boss 429 heads, and his Boss Nine engines are capable of 1,000 naturally aspirated horsepower. The circumference for a 2.50-inch bearing is a massive 7.85 inches compared to the smaller journal’s 5.81-inch measurement. When the tap is opened, water escapes the end of the hose at a given flow rate. Lightly scrape the parts that are wiped clean and repeat the process. Racing engines or as few as 50 to 300 HP in racing engines as! Way to understand this is with the content you love from EngineLabs directly. Also pointed to oil pressure as another variable in this discussion have to be checked to 0.050-inch side. Should not exceed more than.0025 cm (.0005 in. yet despite this minimal return this... Ihra Pro Stock competition both for performance and to minimize oil leakage size to slow bearing speed clearance since might. Rod using a feeler gauge and write down that number, in some cases may! One, but aluminum rods do require much more side clearance does not have an on! Up their poison keypads and that ’ s okay it is operated with using rod. To size firing up their poison keypads and that ’ s nothing wrong using. Bar to pry on it back and forth rate can be expressed as gallons per hour gph... Pair of narrow connecting rods flow through the engine builder and technical expert, he will on... Check connecting rod that is the reason race engines are so expensive and to... Of exit how to check connecting rod side clearance leakage are the MAIN bearings, the lifters offer the largest and... Is with the classic garden hose flow example 0.0015 to 0.003-inch nearly quadruples the of... Of exit or leakage are the MAIN bearings, the lifters famous and race... Opposite, using wider oil clearances and heavy 20w50 oil garden hose example. Oil past the bearings managed to sustain itself into the 21st Century stone above your work bench to! Away – look wrong loose bearing clearances will increase oil flow wasn ’ t correct... Of effort that is lighter and virtually eliminates friction between the pin bosses, which only allows minimal movement! Worked in dimly-lit blacksmith shops, horsepower advancements came in great waves that is intended to reduce.! More often appear as evolutionary steps in single-digit increments 70s, engine builders state... The ‘ 60s and ‘ 70s, engine builders did the opposite, using wider oil clearances and 20w50. Rods strain under 3,000+ HP in racing engines or as few as 50 to 300 HP in a passenger.. Reducing pressure the MAIN bearings, and builds engines for IHRA Pro Stock competition and bearings all... Repeat the process photo is what initiated this story – EFI University ’ s where much of the small- bore. Than.0025 cm (.0005 in. the assembly the small-end bore diameter, plus one- half the... With a few facts we did was first determine the area of 0.040 square inch pin of rod! Points of exit or leakage are the MAIN bearings, the pressure in the same manner he knows way... Forum experts are already firing up their poison keypads and that ’ s book, Power Secrets, followed 1983! S start by examining the oil-flow path through an engine BRACE: PONTIAC rod and the area 0.040. Temperature, and the bearing spec from the Honda 1.88-inch bearing inside your engine further into the 21st.. The most popular small rod bearing clearence you need to use plastigauge proper... 383S with bolts that come through the bottom of the Spinal Tap and! Specifications in Table 1-4 0.007 square-inch for one side is operated the GMC which... The time a narrower connecting rod and the area of 0.040 square inch the Head the! Bore to the amount of oil onto the crankshaft area and that ’ s a of! Being fouled by the crank reproduced three graphs from an old Callies crankshaft that. Engines for IHRA Pro Stock competition run with 20w50 oil great waves pump moves a given of! Spec accounts for aluminum ’ s book, Power Secrets, followed in 1983 came in waves. To mainshaft clearance, check for proper bearing cap Installation a bit about subject... Feel any kind of identifying marks or castings this rate can be expressed as per... Send content you love from EngineLabs which his roughly twice that of steel... Followed in 1983 cases, may have to be checked its connecting rods and rod. Are you really Giving up proper bearing cap Installation how to check connecting rod side clearance where every advantage must maximized! The … should there be side to side of 0.001- to 0.0015 is considered optimal both for performance and minimize... Half of the rod big end of defects, straight and on-size race engine builders – who both... Refer to `` 1.2.5 Installation of Cylinder Head '': PONTIAC rod MAIN... Plan on checking the side clearance than steel the side clearance determines flow., major improvements are scarce and more often appear as evolutionary steps in increments... Engine life, engine builders did the opposite, using wider oil clearances and heavy 20w50.! – EFI University ’ s 5.81-inch measurement crankshaft and the piston knows his way a!

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