Q7 Will the manufacturer guarantee Valvemaster? The manufacturer will be guaranteeing it from a product standpoint, ensuring each batch meets the prescribed specification. Performance in the field cannot be guaranteed since the conditions of use are outside our control. The use recommendations are based on extensive engine testing. Ultimately it is the responsibility of the motorist to ensure correct use and vehicle operation. It should be noted that, in the normal course of events, engines can fail through valve seat recession.