CAM and lifters

Tiny
DILL-11
  • MEMBER
  • 1995 VOLVO 850
  • 2.4L
  • 5 CYL
  • FWD
  • AUTOMATIC
  • 200,000 MILES
Timing belt broke bent valves got another head. Can I take the cam and lifters from my old head and used them in new used head?
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Saturday, June 24th, 2017 AT 10:12 AM

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Tiny
CARADIODOC
  • EXPERT
You should be okay, but what is important to remember is moving parts must be kept together because they develop mating wear patterns. That means a lifter must be reinstalled on the same camshaft lobe. Depending on what an engine uses, push rods stay with the same lifters and same rocker arms, and rocker arms or lash adjusters stay with the same valves. If your replacement head has new valves, they should be okay with the old rocker arms.

The lobes on the camshaft are pitched, or slanted slightly. That makes them contact just one side of the lifter, and that causes the lifter to rotate as it goes up and down. That makes it wear evenly. Valves and push rods are supposed to rotate too, for the same reason. When a used push rod is reinstalled on a different rocker arm, it typically fails to rotate, and a groove will wear into them. That can cause a clicking noise when the engine is running.

Overhead cam engines use a lifter that does not rotate. Those do not actually ride on the camshaft lobe. Instead, they are stationary and just pump up to remove slack between the cam lobe and "cam follower", which looks like a rocker arm and does the same job. Those cam lobes are not pitched because there is nothing to cause to rotate.

Another overhead cam design uses lash adjusters in the tips of the cam followers. They are stroked just like a lifter, and pump up the same way, but there is nothing to cause them to rotate. They rarely contact the valve stem perfectly on center, so the valve is likely to rotate when in operation. There is enough wear from sliding on the valve stem that those adjusters often wear to reveal a pin hole that leaks out pressurized oil. If that gets bad enough, you hear the same clicking sound that a collapsed lifter makes.
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Saturday, June 24th, 2017 AT 8:47 PM

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