Friday, 11 March 2016

Temperature Testing

So, I've planned out a series of temperature tests, to examine the temperatures at which various parts of the engine are running.

The objective is to discover whether all the cylinders are running at consistent temperatures or whether there is evidence of higher temperatures on one or two cylinders, which might indicate excessive friction.

I'm using an infra-red thermometer to measure the temperatures. It has a measurement range of between -50°C and 550°C (between -58°F and 1022°F); you just pull the trigger, it lights the laser to enable you to aim the unit and it will display the temperature on the back. The display illuminates at the same time, and it will hold the value display while you pull the trigger.

The results sheet show details of each test and of the results. I have shown some calculations as I want to record the temperature differences between the cylinders.

Many folk have written about how these engines will see 250-350°F at the top end. Mark Walsh's experience steadies my nerves:

This is pretty much what my own Four is doing at the moment, with considerably less miles on the clock.


  1. I am thankful to find this post. My freshly-rebuilt MKI records in the 350 degree range at all four corners of the engine and I've worried that I am minutes from catastrophe! It's so hot that I can see oil sizzling at the rocker box cover gaskets and the resulting weeping oil on the fins causes embarrassing smoke once stopped (may also be from the pushrod tunnel, yet to confirm). Oil pressure starts at 75 psi and drops well down to near the bottom of the gauge after a 10-mile run. But once cooled it seems no worse for wear - starts on the second kick every time, pulls steadily, and rides amazingly for a 68-year old machine. Best wishes, Mike

  2. Which way around are the oil lines to the cylinder head? The big one goes to the gauge...