Tag Archives: Energy

So You Gonna Build an Engine? Part 3 – Bearings

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Federal Mogul Bearings

Have you even given this a thought?   Nope, not me either.

But here’s why you should and why you shouldn’t go cheap.

Engine bearings have the dual function of reducing friction between a rotating part of the engine (the crankshaft) and the stationary part (the main caps and engine block) and supporting the crank.

Because of the stresses caused by the explosions inside the internal combustion engine, the bearing material must be extremely strong, so a durable metal is required.

Engine bearings are small and relatively inexpensive components of internal combustion engines however failure of an engine bearing commonly leads to serious reconditioning works of the engine including its disassembling, regrinding the crankshaft and replacing the bearings.  Sound like fun?  No.  And we all know that it’s not cheap to rebuild, so let’s do it right and not cut corners in this area.

So what should you get? Well considering that there are all kind of ways to destroy your bearing, like dry starting (no oil coating) some of the following:

  • Wrong selection of the Engine bearing materials for the application.
  • Localized loading of the bearing due to a misalignment (eg. hour-glass journal, distorted connecting rod).
  • Fuel detonation caused by advanced ignition.
  • Running the engine under high loads (torque) at low rotation speeds for long period.
  • Poor conforming of the bearing back with the housing surface.
  • Over fueling.
  • Corrosive action of contaminated oil, which lowers the fatigue limit (Corrosion fatigue).

Yes it’s true bearing take a beating.  Here if you go cheap, especially if you are racing, you go home.

So double up on the cash because quality bearings like Michigan 77 or Federal Mogul competition will cost you twice as much.  Pay now or rebuild sooner.

Michigan 77’s

Thanks for reading.

Tim Sweet

Wrenchin’ Tip – Fuel Delivery

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Here the first Wrenchin’ Tip for 2011.

When installing a new engine or even modifying your present power plant fuel and intake system you have a few things to consider.

Of course the size of your fuel pump, where it and the fuel filter is located, size of the filter, size of your fuel line, fuel pressure.  Along with that jet size or injector size and baffling in your fuel tank.  All of this is important to ensure your fuel delivery system can maintain full pressure at peak engine horsepower in high gear.

All of these need to be adjusted or “sized” to accommodate less controllable factors such as Altitude, air temperature and idiosyncracies of your fuel, like quality and octane rating.  Yes even specific gravity of your gas can effect the jetting.

Here are some jetting requirement of a 750 CFM 4 barrel Holley for specific fuel, temps and altitude options:

Octane                 Temp.            Altitude      Front Jetting      Rear Jetting

  94                        80F                 0 ft                   81                       86

110 Race              80F                  0 ft                 81                       83

94                          80F                3000 ft           76                      81

94                          80F                6000 ft           73                      77

94                          40F                0 ft                 84                      89

94                         120F               0 ft                 78                      83

Oxgenated fuels toss another factor in to be considered when determining your jetting requirements.

Studies of shown that every 1 point richer in air/fuel ratio equals only a few percent less power.  Running the engine as lean as possible will increase your power but also increased combustion chamber temp, which can damage your engine.

Thanks for reading

Tim