Calculating valve spring sizes

Calculating valve spring sizes

This topic has 5 replies, 5 voices, and was last updated 1 September 2023 at 18:44 by john halfpenny.

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1 September 2023 at 12:19 #658748
vintagengineer
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@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?
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1 September 2023 at 12:19 #2663
vintagengineer
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@vintagengineer
1 September 2023 at 12:41 #658753
HOWARDT
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@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.
1 September 2023 at 13:24 #658760
Roderick Jenkins
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@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
1 September 2023 at 15:07 #658764
duncan webster 1
Participant
@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
1 September 2023 at 18:44 #658774
john halfpenny
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@johnhalfpenny52803
Why not look at similar vintage engines?
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