Installing Rod Bolts on Steel Connecting Rods - Engine Builder Magazine

Installing Rod Bolts on Steel Connecting Rods

Do not use metal stamps to number the connecting rods. Metal stamps may disturb the roundness of the rod bore. Paint toolmaker’s layout dye on the rod and cap instead, and then inscribe numbers.

NEVER use bolts to draw the cap down on rod. Locate cap dowel sleeves into the counterbores of the rod. Then, CAREFULLY tap cap into place.

CLEARANCES vary, as to application. Measuring bearing surface at 12:00 o’clock and 6:00 o’clock, the general rule is approximately .001? clearance per 1.000? of crankpin diameter. Wrist pin clearance generally runs from .0007? to .0015?.

OIL PRESSURE: 10 Ibs of oil pressure for every 1,000 rpm is recommended. Thus, 7,000 rpm = 70 Ibs of oil pressure (hot).

Clean all parts thoroughly to remove all dirt and foreign oils. Spread bolt lube on threads and under ?ange of bolt and tighten per instructions below.

For any fastener to supply clamp loads high enough to keep the parts together, it must be stretched the proper amount. Torque does not measure or ensure proper bolt stretch, it measures friction. This is why most experts prefer the stretch method for tightening rod fasteners.

To use the stretch method, measure and note the free length of each bolt before tightening with a stretch gauge or a micrometer with ball end attachments. Then, using the chart below, tighten the bolt until the  proper stretch is achieved.

Bolt Type             Recommended Stretch              Torque & Angle

3/8? ARP 2000        .0052? to .0057?                         25 ft Ibs + 55 deg

As a ?nal check to make sure no bolts were missed: Set a torque wrench at 50 ft Ibs, and check all rod bolts. If any bolt turns before reaching the preset torque, it has not been properly tightened. You must loosen these bolts and tighten them properly.

When removed, if the bolt length changes more than 0.001? from pre-install length, it MUST BE REPLACED. A stretched bolt is worthless and will fail, resulting in engine damage.

–Tech Tip courtesy of Falicon Crankshaft Components, Inc.

You May Also Like

Shop Solutions – January 2024

Before installing cam bearings, make sure to chamfer any oil holes and clean up back grooves of any sharp edges.

Engine Builder and Engine Pro present Shop Solutions in each issue of Engine Builder Magazine and at enginebuildermag.com to provide machine shop owners and engine technicians the opportunity to share their knowledge to benefit the entire industry and their own shops. Those who submit Shop Solutions that are published are awarded a prepaid $100 Visa gift card. Submit your Shop Solution at [email protected]. You must include your name, shop name, shop address and shop telephone number. Submitted Shop Solutions not published will be kept on file and reevaluated for each month’s new entries.

Shop Solutions December 2023

Check out the latest shop solutions from builders around the country.

The Impact of Fuel Type on Engine Performance

When it comes to choosing the right fuel for your vehicle, several factors should be taken into consideration. These factors include the vehicle’s engine design, manufacturer recommendations, intended usage, and personal preferences.

Component Cleanliness

It can’t be overstated how important the cleaning machines are in the modern engine shop. Shop owners who prioritize effective and efficient cleaning techniques will find success in a more streamlined process.

Billet Blocks and Heads vs. Cast Iron

Billet aluminum has a lower yield strength or higher modulus of elasticity, meaning it will flex, or absorb energy easier under tension or stress than cast aluminum, without incurring permanent damage.

Other Posts

Shop Solutions November 2023

Many times, the flange diameter of the rod nuts will contact the radius around the nut seat on some rods. Some jobs may not warrant the expense of spot facing the nut seat on the connecting rods. In that case, it can be quicker and more effective to just machine a chamfer on the ARP rod nuts.

The CNC Landscape Continues to Grow Inside Engine Shops

Several manufacturers named automation as one of the biggest continuing trends surrounding CNC equipment these days, and it’s clearly a key contributor to a CNC machine’s ability to do more without human interference.

Crankshaft Counterweights

Most engines are internally balanced, meaning all weight adjustment is done on the crankshaft counterweights. However, some stock and modified engines require external balancing due to an increased stroke or larger pistons, and the crankshaft counterweights that would be required to offset the increased inertia simply don’t fit inside the crankcase.

Shop Solutions – October 2023

A written warranty provides benefits for you and your customer. It sets expectations, protects both parties and is a great marketing tool that encourages repeat business.