Do I need tool steel wrist pins?

In a racing environment, tool steel wrist pins with a . 090-. 125-inch wall thickness are often adequate for most normally aspirated applications, but big block engines exceeding 800-1000 horsepower, need pins with a minimum .

How much clearance should a wrist pin have?

0.0008- to 0.0010-inch
A typical pin fitting clearance is within the range of 0.0008- to 0.0010-inch to the connecting rod. This clearance is a double-edged sword since tighter operating clearances increase the load carrying capacity but reduce oil flow.

Are bigger piston wrist pins better?

According to Trend Performance manager Steve Rhodey, “the first two requirements for choosing a wrist pin should be the material and then second – the wall thickness.” Wall thickness is a double-edged decision because while a thicker pin is obviously stronger, it’s also heavier.

How do you measure wrist pin size?

If you measure the wrist pin directly, measure it’s outside diameter. You can measure the passage in the piston or the wrist pin while it’s still installed to avoid removing the circlips and pin. Some people would prefer not to disassemble the engine to check the size of the wrist pin before ordering parts.

What causes wrist pin failure?

Assuming a pin properly designed for the intended application loads, typical real world failures are usually lubrication or engine overspeed related. An engine suffering from detonation (pre-ignition) can also contribute to failure.

Do wrist pins have bearings?

In a four-stroke engine under power, the wrist-pin bearing in the small end of the con-rod undergoes regular load reversals. As the rod stops the rising piston at the end of its exhaust stroke, piston inertia pulls up on the wrist pin, but when compression and combustion occur, gas forces push down on the wrist pin.

When should I change my wrist pins?

Usually when the pin is . 001 under its worn by the rod in the middle and if its not parallel anymore replace it.

How do you measure piston pin bore?

Insert the largest thickness feeler gauge that fits between the ring and groove. If the thickness exceeds . 006” (0.15mm), replace the piston. Measure the pin bore for size and out-of-round, as per manufacturer’s specifications.

How do you measure a connecting rod bore?

Using an inside micrometer, measure the diameter of the small-end bore. Using an inside mic, measure the diameter of the big-end bore (with cap installed and fully torqued to spec). Take this measurement from the 12 o’clock point (center of the rod saddle radius) to the 6 o’clock point (center of the cap radius).

What does a wrist pin knock sound like?

Wrist pin knocks fall halfway between lifters and lower end noises. When it get bad it will knock on the upstroke and down stroke sounding something like a lifter. With the engine running and knocking, pull each plugwire one at a time. When you get to the bad cylinder the noise will almost go away if it’s a wrist pin.

Where will cracks show up on piston pins most often?

General information about piston pin fractures Under excessive loads a longitudinal crack can form at the ends of the piston pin, with its starting point either at the outer or inner diameter of the pin. The crack then spreads as a fatigue fracture towards the centre of the piston pin.

What material are wrist pins made of?

alloy carburised steel
Piston pins are made of alloy carburised steel.