two technicians are discussing connecting rod side clearance

two technicians are discussing connecting rod side clearance. Technician A says that if the clearance is too great, the crankshaft may require replacement. Technician B says that excessive side clearance may decrease oil pressure when the engine is running. Which Technician is correct?

A. Technician A only

B. Technician B only

C. Both Technician A and B

D. Neither Technician A nor B

Solution

Excessive side clearance can cause high oil consumption by allowing too much oil to be deposited onto the cylinder walls. With steel rods, .015 - .020 is prefered in a high performance engine while a street engine can generally run with much less. Measurment is between the rod pairs.

If side clearance is too small, the sides of the rods can be sanded to increase the clearance. If too wide, another set of rods is needed.

Reducing the oil clearance between the rod and main bearings and the crankshaft has a number of advantages. A smaller gap spreads the load over a wider area of the bearing surface and distributes pressure more uniformly across the bearing. That’s good, provided the bearing is strong enough to handle it. A smaller gap also decreases the volume of oil that has to flow into the bearing to maintain the oil film between the bearing and shaft.

both technicians Aand B are correct