My '80 B21 has a solid crank pulley. No rubber insert which seems to fail often in newer 240s.

The timing isn't effected when the rubber loses grip as the timing belt is run by the crank gear. It's the alternator, water pump, power steering and a/c pump which stop moving. And they're already isolated from the crank by the rubber belts. So why the rubber insert?

Why isn't the pulley solid? Or why can't you weld the two sections together?
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1980 245 Canadian B21A with SU carb, M46 trans, 3:31 dif, in Brampton, Ont.

Volvo did not pay for a damper pulley and consider their failures lightly.

The alternative - ruined engines - was worse.

Some might consider damper pulleys unnessary, but a LOT of car makers used and still use them.
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'96 855R,'64 PV544 driver, '67 P1800 basket case, '72 Yamaha Rd400, '68 Honda 350-4, '12 XC70, the first 5 are mine, heh, heh, 525,000 miles put on 10 bricks James A Sousa

Hi Trev 29,

FYI.

"Every time the cylinders fire, torque is imparted to the crankshaft. The crankshaft deflects under this torque, which sets up vibrations when the torque is released. At certain engine speeds the torques imparted by the cylinders are in synch with the vibrations in the crankshaft, which results in a phenomenon called resonance. This resonance causes stress beyond what the crankshaft can withstand, resulting in crankshaft failure."

http://en.wikipedia.org/wiki/Harmonic_balancer


I wonder if you can weld the two sections together like you have suggested. And then place a some sort of damper in between the pulley and the mounting plate? Just a thought.

I had this problem in a Cessna 182. TCM used airmelt forged crankshafts, and the "Perfect Storm" RPM, the one that resulted in harmonic resonance, was 2250 RPM, which was right in the engine's sweetspot for optimum cruise. The airmelt process (as opposed to the vacuum melt process) left impurities in the forging, which resulted in weak spots.

There was no dampening of the crank, and the one in my co-owned airplane snapped. While my a/c partner was flying. At 7,000 feet. At night. In the clouds.

Luckily, the crank split across a facing, and it did not fly apart, taking the propeller with it. Bill glided down to a convenient airport and landed safely with no power.

There were several similar failures, and TCM eventually did an FAA mandated recall.

A split crank is not as dangerous in a car, but it is inconvenient and expensive, so I'd stick with the Volvo engineering on this one.

The B21 engine used a forged crank that could withstand the flexing caused by this secondary pulse.

http://www.brickboard.com/RWD/volvo/1489551/220/240/260/280/replace_b230_crank_harmonic_balancer_b21b23_metal_pulley.html