Calculating valve spring sizes

[vintagengineerParticipant @vintagengineer]

I am building GN cycle car engine with some OHV heads. I am stuck on how to calculate the valve spring length and poundage?

[vintagengineerParticipant @vintagengineer]

[HOWARDTParticipant @howardt]

Is the force you need for the spring or the spring details?
Spring manufacturers have online calculators these days but I use an old book which relates wire diameter to spring force in a table, so quite easy to look up with a quick calculation.

[Roderick JenkinsParticipant @roderickjenkins93242]

If you are trying to determine the spring force that you need to keep the cam follower in contact with the cam then you need to know the weight of the valve gear being moved and the acceleration due to the cam at the maximum speed of the engine – Force = Mass x Acceleration. If the cam has a flat follower than CamCalc can help give a figure for the theoretical maximum acceleration which will act as a starting point for determining the correct spring size.

CamCalc dropbox link

Rod

[duncan webster 1Participant @duncanwebster1]

Should you add half the mass of the spring as well? Make a guess in the first place as the design isn't fixed

[john halfpennyParticipant @johnhalfpenny52803]

Why not look at similar vintage engines?

[Author]

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