Remove the bearing cap, wipe the journal and bearing shell clear of oil.Place a piece of Flexigauge across the bearing at the crown.Install the bearing cap and using a Torque Wrench tighten the bolts to the correct tension.DO NOT REVOLVE THE SHAFT OR BEARINGS.Remove bearing cap.

What is a Flexigauge?

Flexigauge is a precision manufactured plastic strip. It is available in four sizes and is used to check clearance of main and connecting rod bearings, and is suitable for Automotive, Marine, and Industrial applications.

How is Plastigage used and how does it show the bearing clearance?

Plasitgauge is a proprietary system for measuring clearances between fitted surfaces of machine parts, such as crankshaft or camshaft bearings. Made from a special extruded plastic thread with accurately controlled crush properties, Plastigage provides a fast and accurate way to check bearing clearances.

Do you use oil with Plastigage?

A modern engine is a little better off, as the insert is a little harder then babbitt, but you can still improve the Plastigages use, by using oil. To remove the used Plastigage from Shaft, and Bearings, Lacquer Thinner, will take care of it fast.

How do I use Plastigage?

Apply a smear of grease to the journal and small quantity of silicone release agent to the shell. Trim a length of PLASTIGAUGE to fit across the journal using the grease to hold it in place. Replace the shell and tighten the set-screws to the recommended torque setting – without rotating the journal.

What does undersized bearing mean?

An undersized bearing has extra material thickness on the inside of the bearing facing the crankshaft journal. Undersized bearings are used when a crankshaft has been machined or ground undersize. Oversize bearings have more material on the outside facing the bearing housing bore.

Why do you use Plastigage?

Plastigauge provides a simple and effective method for the measurement of clearance (separation) between fitted or hidden surfaces. It is particularly useful for measuring clearances in split bearings, or in situations where a feeler gauge cannot be inserted.

What color is Plastigage?

It comes in three diameters and colors. It is color coded by size — green Plastigage measures the range . 001 – . 003”, red measures .

How do you measure oil clearance?

For these reasons, bearing clearances are specified as “vertical clearance” and must be measured at 90 degrees to the split line. The best method of measurement is with a dial bore gage that measures the bearing inside iameter when the bearings are installed at the specified torque without the shaft in place.

How do you check the bearing clearance on a feeler gauge?

1. Step 1 – Insert feeler gauge. …
2. Step 2 – Move blade back and forth. …
3. Step 3 – Take another measurement. …
4. Step 4 – Take additional readings.

Article first time published on

How much play should a crankshaft have?

Provided it’s within manufacturers’ specs, some crankshaft movement is necessary and normal, but either insufficient or excessive movement outside the normal range can eventually damage other parts. On a traditional small-block Chevy, the endplay should be 0.0020. 006 inch.

Is plastic gauge accurate?

Tech Tip: Be sure to always use the inch side of the Plastigage package. … Most good micrometers will measure down to 0.0001 inch (one ten-thousandths of an inch), which is plenty accurate.

How is Cam Journal measured?

Measure the camshaft bearing journals with a micrometer. The cam journals should also be measured at 90 degree angles to determine elliptical wear. Subtract the smaller reading from the larger.

What is the typical connecting rod bearing clearance?

The Rule of Thumb The factory specs include 2.450-inch main bearing journals and 2.100-inch rod journals, which means the target bearing clearance should be about 0.0024-inch (0.0025 is the common spec) on main bearings and 0.0021-inch on the rod bearings.

What is the purpose of bearing crush?

By increasing surface contact between the bearing and the connecting rod housing bore, crushing reduces bearing movement, helps compensate for bore deformation, and aids in heat transfer. In simple words, the bearing crush is what keeps the bearing in place.

What is undersize and oversize?

An oversized bearing has the same inside diameter but a bit more material on the outside diameter. An undersized bearing measures the same outside but is thicker on the inside.

When bearing oil clearances are too large?

However, too large a flow of oil leakage may cause a drop of oil pressure and even oil starvation, which terminates hydrodynamic lubrication. Oil leakage from a bearing with excessive clearance may be reduced by changing to a higher viscosity oil. The influence of clearance on oil flow is seen in Figure 6.

What is the standard rod bearing size?

These bearings generally come in four sizes: standard, . 010 oversize, . 020 oversize and . 030 oversize.

What is the correct gear ratio from crankshaft to camshaft?

4 Stroke engine crankshaft/camshaft gear ratio is always 2:1, which means that for every two revolutions of the crankshaft the camshaft will rotate through one revolution.

Which tool is best for measuring oil clearance on crankshaft bearings?

The dial bore gauge measures the inside of round holes, such as the bearing journals. This one tool can measure 2″ up to 6″ diameter holes. Both tools are needed in order to check the interior and exterior dimensions of the crankshaft, rods and engine block journals, as well as the thickness of the bearings themselves.

What tool measures clearances?

Product Description. Plastigage (also called Plastigauge or Plastic Gauge) is a measuring tool for measuring plain bearing clearances, especially in engines.

How do you take bearing clearance?

The commonly accepted rule that most crankshaft manufacturers prefer for street and performance engines is 0.0010-inch for every 1-inch of journal diameter. So for a 2.45-inch small-block main journal, the bearing clearance would be 0.0024-inch.

How do I know if my rod bearings are bad?

In many cases, a bad rod bearing will lead to a “check engine oil” light being displayed on the dash. However, depending upon the severity of the problem with the bearing, the light may or may not go out after the engine runs for a few minutes.

Which tool is used to check the internal clearance of the bearing?

For accurate bearing clearance measurement SKF Feeler Gauges are designed to measure the internal clearance when adjusting spherical roller bearings.