Monday, 8 August 2016

Oil Pressure

So how is the oil pressure situation now we are into the summer riding season? Amelia's engine is loosening up nicely but I am nervous every time I dip my head to look at the pressure gauge between my knees. This summer, we are in the low-mid twenties (degrees C) and the gauge is still showing the 10 psi at idle, 25 psi at 40-50 mph that Mark Walsh described in this blog post:

http://ariel-square-four.blogspot.co.uk/2015/03/temperature-testing.html

My initial runs were done on a cheap 20W/50, followed by Morris SAE 50. Nothing wrong with this oil, but with a new build engine it was difficult to start and after a few hundred miles the gauge was dropping to near zero at idle. I then discovered Penrite Shelsley Heavy, which is 40W/70 and is designed for older engines with some wear - you all know that my big ends have not been reground and are near the factory wear limit; I did this because they were just about within tolerance and I did not want to risk ruining my cranks with a poor grind.

With this oil, it's quite difficult to turn the engine over in the winter (down to zero Celsius), but there is a Shelsley Medium (25W/70) which I might try; the upside is that the pressure is always above 10 psi, and sees 25-30 at higher speeds. The engine is loosening off now and the bike is starting to really fly! I'm hoping that the loosening off will see some reduction in temperature which in turn will increase the oil pressure a little.

The real truth though is that I am going to have to bite the bullet and get the big ends reground at some point.

Watch this space!

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