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.015, I know this is too much but the engine has less than 5k mi on it. What would have caused this? I didn't measure it when it was built. I put my dial ind. on the flywheel and pried it back and up front I pried the balancer forward. Is this way sufficient?
 

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With the oil pan on that is the only way you can thrust the crank. Unless you want to do like I have done and rig up a way to do both from the front. But I don't think you need to go to such ends.

You should double check your measurements, and be sure your indicator isn't moving on the base. My indicators are old and worn out, and I have to tighten hell out of em or they lie to me. After you get the indicator set tap the face with your fingernail a couple times, it should stay zeroed.

Yup .015 is a ton on a 5k car engine. You're probably not in danger yet but you need to figger out what is going on.You want to look at things that can shove the crank, like the tranny. Whether or not the tranny is pushing the crank forward you need to rectify/identify the excessive thrust situation because if it gets much worse your oil ports will not align like nature intended and you'll push the pistons a little off center. The job of the thrust bearing is to center the crank and limit endplay. Center the crank.... on the oil holes, on the cylinder bores etc.
Was the crank used? It may have been worn on the flanges to begin with. Another possibility is crank to bearing compatibilty. There's guys putting 350 cranks in 400's and vice versa and grinding 400 cranks to 350 mains. I don't have my old Chilton book in front of me, but I bet a 400 crank has a wider thrust than a 350. I see you are a 383, this may be what you have going on. Look up some specs Patrick. Or go down to NAPA and see if they have a 350 and a 400 rear main you can throw calipers on. I'm curious what you find, because I am planning a budget 383 build.
 

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I am thinking in line with Wolf, check that crank flange, My bet would be its either worn or someone redressed it before because of being worn. The stiff clutches cause this. You have twice the amount recommended. You can live with it as long as you dont sit at light with the clutch to the floor too much.
Long ago when I ran 3300# long style clutches in my G/modfied sbc, I had this problem, With epoxy, I built a little dam or cavity in the main cap, to retain oil, excessive wear was still there on crank flange but it got no worse after that.
If this is an AT car, I would not worry about it for now.

If crank flange is not worn, you could go look at other main bearings and put a caliper on the bearing width at the lip, Select bearing of your choice and use it. Saw Don Garlits do this so if it worked for him, good enuff or me.

Looks like Taterhead is listening to you. Maybe he has an idea.
 
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