Hi all. Just throwing it out to any1 who is upgrading the valve train on 340s, the installed height of each valve spring are not the same. The intake valve height is about .060" taller than the exhaust valve due to the casting of the spring seat in the head being that much lower and the use of a stock shim on the exhaust side. So if your looking into valve springs keep in mind u will need about .060" of shim for the intake side so they are both set at the same seat pressures. Can any1 tell me if the same is true for gx 390s?