Author Topic: Valve spring loads  (Read 911 times)

Offline Roger B

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Valve spring loads
« on: January 21, 2019, 05:39:28 PM »
So as not to hijack Steve's thread I will put some values from my engines here:

Original 25cc horizontal engine. This used the valve gear from an army surplus battery charging set. Opening load around 4.5 kg (lump of CI 90 dia x 100 long) Valves around 13 mm diameter.

3cc vertical engine. Uses DIY supermarket springs. Opening load around 1.2 kg (test weight from fuel injection experiments) Valves 6mm diameter.

Updated 25 cc horizontal engine. Uses DIY supermarket springs. Opening load around 2.8 kg (Lump of CI 50 dia x 200 long) Valves 11mm diameter.
Best regards


Online Vixen

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Re: Valve spring loads
« Reply #1 on: January 21, 2019, 05:54:32 PM »
I measured the force require to crack open the valves on a number of my 4 stroke engines. Most engines required a force of between 1lb to 2lb (approx 0.5 to 1.0 kg) applied to the end of the valve stem to start to open them. The only exception was my Seidel 5 cylinder radial which required a force of 4 lb (approx 2.0 kg) to start to open the valves.

It's was not that difficult make the measurement using a long push rod to apply the force to an upside down spring balance. File a V in the end the push rod where it pushes against the spring balance's hook, to stop it slipping off

Sorry about the shaky photo, pressing the camera button with my left hand


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