7.8 timing

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Nov 5, 2016 | 10:17 PM

79sparky

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7.8 timing

Rebuilding a 7. 8 , after I line up the O marks on the crank and cam gear to the idler gear and spin the motor by hand the marks never line up again is that normal or is there something I'm missing about this motor ? Thanks

Nov 7, 2016 | 06:16 PM

85e150

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If the cam and crank never line up again, you have something really wrong with the gears. The cam runs at 1/2 crank speed, and unless you have variable valve timing, which you don't, never changes position relative to the crank.

Are you working out of any kind of repair manual?

Nov 7, 2016 | 10:02 PM

79sparky

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No the crank and cam line back up as they should at least by the naked eye. Just not with the idler pully though thinking of it more, it would appear the idler gear is about half the size of the cam and ip great and about twice the size of the crank gear so it would be spinning at a different rate and may lead to the O marks on the idler gear not lining back up sheet installation . Probably just have to spin it more revolutions for them to live up with the idler gear. But that's just what I came up with thinking of it more. Also, no I do not have a service manual. Have the torque specs and that's all I generally need just found it odd the idler gear o makes didn't live back up with the cam and crank gear o marks. Normally I work with v-8s where the timing gates are stacked. Maybe this is general practice for engine designers to size the idler gear as such with l6 motors?

Nov 8, 2016 | 07:39 AM

chrissmallwood

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The timing marks on the engines we build at work do not line back up once you begin to rotate them until you have spun the engine about 35 times. It might be the same on yours where once you've been through so many revolutions the timing marks finally come back into alignment. Its either a "hunting" or "non hunting" gearset, I cant remember which one works in this way.