Hello, I am rebuilding the cylinder head on a 401 from my 1962 Electra 225 and found it had valve spring shims installed. The cylinder head was last rebuilt (very badly) when the car was at 58k miles. The car gained 2k miles and then sat for 28 years (1986-2014) What is the reason for the shims? Do they necessarily need to be kept? Thanks Joe
Shims are generally used to increase the spring pressure a bit on a used engine. Could be 2 reasons to do so: 1) It's cheaper than replacing valve springs. 2) If a valve job was done, the valve get sunk in the head a little, which increases the spring 'installed height'. Shims are used to reduce the installed height and get it back to spec. Shims were also a cheap 'old school' trick to increase pressure for higher rpm use.
yep,, old school trick to get a few more rpm....On a nail head I usually go about .060 or so...... :Brow:
