Hello, I have a john Deere 4520 and the engine is a 4024TLV07. The tractor stop running one day and I found that the cam gear bolt had come loose and the cam was not turning with the crank. There is no key way on the camshaft so it appears the gear can go on anywhere. I trying to find out how to time the cam to the crank. I had planed on finding top dead center and bolting the gear on. I just know a couple of degrees can make a big difference if its not right. Any help will be appreciated.