Engine - Cylinder Head Bolt Design Change
Head Bolt Design Changed for V6 EnginesNOTE:
This article applies only to '05 Honda V6-equipped models built in North America. In July '05, our Ohio engine plant and Alabama factory changed the type of cylinder head bolts used to assemble V6 engines.
The original head bolts were 6-point, elasticity range bolts. You tighten these bolts using a threestep torque method. The new head bolts are 12-point plasticity range bolts. You tighten these bolts using a torque angle method.
As a rule, you should never mix these two different bolt types. Mixing the bolts, or switching between their bolt tightening methods, could cause bolt failure or cylinder distortion. Always order the same type of head bolts that originally came with the engine. If for instance, the engine came from the factory with 6-point bolts, don't order 12-point bolts, even if you're replacing all the bolts. The parts catalog lists both types of bolts for '05 vehicles. You can take the guesswork out of ordering if you've got the vehicle's engine number handy.
Before reusing 12-point bolts, you need to measure the bolt diameter in two places. If either diameter is less than 11.3 mm (0.44 in.), you must replace that bolt. If you're using 6-point bolts, you can keep using the same ones again and again, unless, of course, they're damaged.
If you're using 6-point bolts, follow the three-step torque method in the appropriate S/M. If you're using 12-point bolts, follow the torque angle method in these steps:
1. Apply fresh engine oil to the threads and under each bolt head.
2. Use a beam-type torque wrench to torque the bolts in sequence to 29 N.m (22 lb-ft). If you're using a preset torque wrench, make sure you torque them slowly to prevent overtightening. If a bolt makes a noise while you're torquing it, loosen that bolt and torque it again from the first step.
3. When you're done torquing all the bolts, tighten them further in two steps (90 degrees per step) in sequence. If you're using a new bolt, tighten that bolt an extra 90 degrees. If you tighten a bolt beyond the specified angle, remove that bolt and remeasure its diameter.
Replace the bolt if needed. Don't loosen it back to the specified angle.
IMPORTANT:
Make yourself a copy of this article, and keep it at your workstation. Not all S/Ms include this 12-point head bolt info yet. Those S/Ms will be revised at a later time.