The importance of emulsifiable grinding oil during engine head resurfacing

When we talk about engine head resurfacing, with a grinding wheel or abrasive sector, one of the aspects that most affect the quality of the finish is definitely the emulsifiable grinding oil used during this process.

Surely often we pay extreme attention to the abrasive grain, to the revitalization of the sector or of the wheel, to the speed of rotation and advancement, but a few times the importance of emulsion fluid is taken into account.

Therefore, speaking of refrigerant during the flattening of the heads, the aspects we have to take into account are mainly 3:

  • Mixing ratio of water/emulsifiable grinding oil
  • Output jet inclination
  • Output pressure of grinding coolant
Emulsifiable Cutting Oil in an engine resurfacing machine Comec RP900
A Comec RP900 resurfacing machine during grinding of an aluminum engine head.

Mixing ratio water/emulsifiable grinding oil

To obtain maximum performances during the adjustment of the engine head, the emulsifiable grinding oil should be mixed in the correct proportions.

Normally, the theory provides a mix of water/emulsifiable grinding oil in a ratio from 4 to 9%.

However, at The Ultimate Tooling we recommend that you carefully follow the instructions given by the emulsifier manufacturer for an optimal blend.

Grinding Coolant jerry can for engne heads resurfacing
Emulsifiable grinding oil tanks for grinding.
Goodson CGC-1288 All Purpose Grinding Coolant
Goodson emulsifiable grinding oil for grinding

Output jet inclination

Another particular consideration is the output jet inclination that the nuzzle must have when spraying the emulsifiable grinding oil on the grinding wheel.

Always referring to the theoretical advises, the correct inclination that the nozzle should have to reach the best achievable result is 20° with compared to the tangent of the grinding wheel.

Output jet inclination of emulsifiable grinding oil in the engine heads resurfacing
The correct inclination of the grinding coolant jet compared to the tangent of the grinding wheel should be about 20°

Output pressure of grinding coolant

Lastly, but not less important, is the output pressure of the emulsifiable grinding oil.

The output pressure of the emulsifiable grinding oil mostly determines the flow rate of the grinding coolant.

We can translate the output pressure into the amount of emulsifiable grinding oil that will be into into the grinding wheel during the process.

This aspect significantly affects the temperature produced during resurfacing.

The grinding coolant speed is correct, only when the output pressure is approximately equal to the peripheral rotation speed of the grinding wheel.

Inadequate emulsifiable grinding oil output pressure of the grinding coolant
Inadequate output pressure of grinding coolant
Optimal emulsifiable grinding oil output pressure of the grinding coolant
Optimal output pressure of the grinding coolant

Let’s try to refer to the data shown in the table below, where VM will be the peripheral rotation speed of the grinding wheel, while PK will be the output pressure of the grinding coolant:

VM (m/s) PK (bar)
Correct Min
10 1 0,6
20 2 1,2
30 5 3,2
40 8 4,8
50 13 7,8
60 19 11,4


The advantage of an optimum mix of emulsifiable grinding oil could be resume into the following points:

  • Increased material removal
  • Improved surface finish
  • Reduced risk of burnt spots
  • Longer life of grinding wheel or abrasive sector

Final considerations

It should be specified that in some cases, as in the situation of tangential grinding machines, lot of people prefer to use pure and unmixed grinding grinding oil.

However, we want to point out that into engine repair, tangential grinding is mostly rare.

Also, we would like to clarify that we always suggest to use emulsion liquids from the best brands.

This will allow you to get the best performances of your resurfacing and to maximize the benefits listed above.

Emulsifiable grinding oil for engine heads and blocks resurfacing
Tangential grinding of a flat surface


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