Motor Bearings General Info

Bearings, something simple but yet so complicated. Choices of brands, materials, clearances, and applications, all have an effect on the longevity of your motor as well as how it performs and wears.

Main, rod, and thrust bearings are the life of your motor. One small miscalculation may cause catastrophic failures that can result in needing complete engine overhauls to requiring a complete engine replacement.  There are plenty of choices when it comes to manufacturers and bearing types. There are bearings ranging from direct OEM replacements to full race applications, depending on your needs. Each will be composed of different materials and constructed through different methods.

Clearance is an issue that needs to be taken into consideration. Race engines will run tighter tolerances for maximum performance. At high RPM levels, the oil pump is pushing a higher volume of oil and at a higher pressure than compared to a car at idle or driving around town. Tighter tolerances allow for higher oil pressure to occur between the moving components, allowing motors to run at very high rotation without losing pressure and running a chance of bearing to moving part contact. However, running too tight of a tolerance will cause excessive drag to occur on the moving components, along with the possibility of metal-to-metal contact unless the motor is pre-heated.

Street cars will typically run a looser tolerance to allow proper lubrication at different temperatures. OEM bearings are designed for longer service life instead of high stress and high heat like that exposed to race application bearings. So unless you plan on participating in heavy racing and frequent motor rebuilds, full race bearings might not be the best choice for your application.

The next time you are putting together a motor, consider these things as the bearings are in the heart of the motor and a single failure could potentially cause great damage to a motor.

If you have further questions or would like to make a suggestion for our next article, please email law@rallysportdirect.com

Since we are on the subject of bearings, below is an email from Cosworth regarding their bearings and sizes.

Hello,

We get a lot of questions about our bearings, most customers get confused and think that we offer oversized bearings, however the size differences we offer are for oil clearance and not to compensate for ground crankshafts. This is good information to forward to customers if they have any questions about our bearings.


COSWORTH BEARING FACTOIDS:

§ Our bearings are available in 3 sizes: 0, 1, 2.

§ All three sizes are within the “standard” range. We do not offer undersized bearings for ground crankshafts.

§ Size 1 is what we used to call “STD”

§ Size 2 is what we used to call “RACE”

§ Size 0 provides .025mm or .001” less oil clearance than our size 1 bearing

§ Size 2 provides .025mm or .001” more oil clearance than our size 1 bearing

§ Bearing half shells can be mixed and match to provide the incremental changes in oil clearance

Cosworth Ultra High Performance Engine Bearings

Engine bearings are one of the most vital components within an engine and are often overlooked when considering high performance upgrades. Performance engineered, multi-layer bearings generate less heat than normal bearings by reducing friction. Cosworth bearing sets feature unique combinations of design, metallurgy and engineering to deliver performance in extreme conditions. Cosworth bearings sets are available in three sizes to accommodate most applications.

Engineered with the following features:

■ High strength overlay plate with reduced thickness for better oil control and less friction

■ Hardened steel backing on all connecting rod bearings

■ Increased crush for better retention

■ 3/4 grooving on Main Bearings providing optimum oil supply

■ Tight consistent wall tolerances

■ Oversize chamfers where applicable

■ Flash plating eliminated for improved heat transfer

■ Tested to over 1000 horsepower

FAQ

Q: Why don’t you offer bearings for re-ground crankshafts?

A: Grinding most modern crankshafts will jeopardize the surface hardness or heat treating that

was applied at the factory and will compromise the reliability of the crank in performance applications. Since we are not catering to the standard rebuild community, we do not offer a bearing to suite the ground crankshaft.

Q: I have a 1999 Subaru GC, will your bearings fit?

A: Typically the rod bearings will be ok if your rod journal is 52mm. Our main bearings will only work in the later 2001+ engines with the thrust in the 5th position (next to flywheel). Earlier engines have the thrust in the 3rd or center journal.

Q: Do you have bearings for the Nissan VQ35HR

A: No, the HR version has all new journal sizes and we do not offer bearings for the application.

Q: Why are Cosworth bearings better than original bearings or other performance brands?

A: Cosworth bearings are manufactured from superior materials compared to most OE bearings and to tighter tolerances compared to other performance brands.

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