Jaguar: XK8 4.0 to VIN...A30644, XK8 4.2 from VIN...A30645 to B32752, XK8 3.5 from VIN...B00379 to B32752, XK8 5.0 from VIN...B32753, X350 3.5 and 4.2 V8 from VIN...G00442 to H32732, X351 5.0 V8 from VIN...V00001, all XF 4.2 and 5.0 V8, all S-Type 4.0 and 4.2 V8, X308 (XJ8) 3.2 and 4.0 from VIN...812317 to F59525
These so-called stretch bolts are specifically designed to give a set length under the right torque. As such they should never be used a second time. The desired bias requires careful installation. The cylinder head bolts are assembled in several stages with a specific tightening torque. When this torque is reached, the bolts are turned further through a defined angle which pre-loads them into a plastic region. We recommend that new cylinder head stretch bolts be used and any work carried out to your engine is done in accordance with a factory workshop manual. Whilst you are doing this job we consider it advisable to replace the water pump and expansion cap to minimise any future problems.