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OFMF
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I am looking for min - max crank & cylinder tolerances for the 70 350. If someone has a link, I would appreciate it. I know the Bore is 4.000. The rod journal is 2.10 and the main journal is 2.45. Just need to knowhow far out I can be for each before I need machine work. Thanks in advance.

Pat
 

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On the crank anything less than .0015 is not enough and anything over .003 is too much. As for the piston to bore tolerence depends on what the piston manufactuer recommends for that piston. If the crank and bearings mic out at .0015 your okay, anything less than that is not enough. Cast, Hyper and forged pistons all have differenct tolerances and that`s why you should refer to what they recommend.
 

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WFO
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WesTXmc said:
I am looking for min - max crank & cylinder tolerances for the 70 350. If someone has a link, I would appreciate it. I know the Bore is 4.000. The rod journal is 2.10 and the main journal is 2.45. Just need to knowhow far out I can be for each before I need machine work. Thanks in advance.

Pat
HERE ya go. Or hit up the local library. Or trust it to your machinist.

One old saw says that if the copper from a penny rubs off when rubbed across the crank journals, it's too rough to just polish. Now that the fedgov has been plating copper over a zinc slug, I don't know if this still holds true- if it EVER did.

This says nothing about taper- you can try to use plastigage to see the taper, as well as the oil clearance- but this is not very accurate at all. Much better to accurately measure w/the correct tooling.

The thrust surfaces of the crank need to be checked, too. This should be done before the crank and bearings are removed from the block in order to get an idea if there's a problem there. If the crane's already out, hie it off to the shop to have that checked. Otherwise, if you have the journals turned then find out the thrust is out, you will be hating life.

The bore's condition can be determined by looking closely at the lip left at the very top of the cylinder. The difference between the unworn top and the worn surface below that is how much the bore has worn. But then there's taper as well. Either measure it with a bore gage or take it in to be measured, along with having everything checked for cracks, etc.
 
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