I'll second Larry's advice for the retainer method, if you need to use it. BUT:
The most likely reason the cam gear slipped in the first place is the gear was replaced once already WITHOUT the crank gear also being replaced. I've seen that a couple of times where a new cam was been installed with a new gear. They used an aluminum gear when the original was a fiber unit. The backlash for fiber and aluminum setups is enough different that it won't work for long. The aluminum gear hub gets pounded out because there isn't enough clearance between the gear teeth.
Always use a matched set when replacing these things. Don't cut corners by trying to get by with only one gear. If the cam slips out of the press-fit gear, the timing can retard about 15 degrees. If the crank bobs don't hit, it'll slip again, possibly knocking out the coreplug in the back of the motor for a major oil leak.
The owners were operating the engines at sustained high RPM climbing hills, which was making for maximum heat and oil pressure. That combination caused maximum thrust from the distributor drive (oil pump) to pull the cam right out of the gear.
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David
newbie #4153
