Exhaust valve seat insert 320/A2552 JCB Dieselmax, genuine

Exhaust valve seat insert 320/A2552 is a genuine JCB part for the JCB Dieselmax 444 engine.

The valve seat insert is a hardened ring pressed into the cylinder head; the combustion chamber seals on it when the valve closes. A burnt, cracked or over-cut seat lets the valve sink, loses compression and burns the valve. The insert is replaced when it can no longer be recut. The seat carries heat from the valve head into the cylinder head, so a tight fit matters for valve cooling. A loose insert can drop into the cylinder and cause serious damage. The Dieselmax has two inlet and two exhaust valves per cylinder. Exhaust seats run hotter than inlet seats. The seat insert is supplied new and unmachined.

Specifications

Compatibility

The part is listed for JCB 3CX and 4CX backhoe loaders. Other parts are in JCB Dieselmax engine.

Fitting

Renew the valve and stem seal when the seat is replaced, and set the valve clearance once the head is back on. Measure the bore in the head; if the insert fits loosely, a new one is not fitted without machining the head. Check the valve guide before cutting the seat.