Checking valve clearances

[Tev62]

Valve checks are often misunderstood by owners and possibly many dealer mechanics too. When a manufacturer gives a clearance range, say 0.14mm - 0.20mm they intend you to leave the shims well alone, if when measured, they are anywhere within that range including the outer limits. They are expecting another check at the next interval and have allowed for extra wear. They are not concerned on the next check if the value ends up at 0.12 or 0.23, they have allowed for this and that is when they expect you to change the shims.

There are plenty of owners and dealers who seem to think the middle value of 0.17 (in my example) is the ideal target gap and re-shim to that. Taking this approach will be the difference between taking the camshafts out every single service interval and possibly not taking them out for the next 100,000 miles.