My 6.1 retrofit thread
do you think those shims on the intake are necessary? I didn't use them since made this swap. Stock engine btw....
Yes..definitely - on the INTAKE side - its the only way I could achieve the correct installed height with the PSI spring
Here's what you need to know -
1st..the psi spring has a different big end ID....This means you use a custom locater and an aftermarket seal on BOTH the intake and exhaust side.
Get rid of the cages and the factory combo seat/seal.
2nd- The requirement for shims will depend on what is needed to achieve the recommended installed height of the PSI spring.....and that is dictated by the depth of the factory valve seat and cast height of the spring pad. This can vary because we are dealing with factory tolerances.
Because you are dealing with factory tolerances...this can vary from head to head and even from valve to valve....although the G3 heads have a reasonable reputation for consistency.
Remember also...the installed height of the factory springs is different to the PSI - and the intake is different to the exhaust.
3rd - After removing the factory spring seats, I was able to get away with just using the .060th locater and aftermarket seal on the exhaust side for an exact 1.80 install height.
BUT - I needed two shims AND a locater to achieve the same on the Intake side
Did u measure your installed height?
Did you swap the factory combo seat/seal out'?
