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Discussion Starter #1
I am putting together a 1750 motor and my sense is that the crank is not spinning as freely as it should. The shortblock with everything in and tight (no plugs, no cams, with pistons) takes a ratchet to move the crack. Once it is movng it spins smoothly and requires not too much to keep it going. I started to dismantle it slowly to see if I could catch the binding element but I got right down to a bare crank unbolted on the mains and it still requires some effort to start it spinning. In this case you can spin it by hand but I would think it should spin with virtually no effort. I had the crank ground and have OS bearings. When I first put it together (last month) I checked the gaps with plastigauge and they looked good. I am going to retest it but I am out of plastigauge at the moment. I am also going to check the crank for concentricity. Is there anything else I should look at? Or am I making a mountain out of a mole hill? The front main bearing showed some minor wear (shiny) along the side but I would think that it is designed to wear in some. All the bearngs are well lubricated.



Thanks in advance for your advise...

- Rich
 

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Without pistons should be able to spin a lubed crank with your wrist, easily.

Atleast it sounds like it is not bent ... I've been there and experienced that.
Pete
 

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Trained (ex)Professional, , 1953-2018 RIP,
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16,232 Posts
Well, with the pistons installed, yes, it'll take some effort to get the thing spinning. But like Pete says, just the crank alone should spin easily by hand. If it doesn't, I'd recheck all bearing clearances and crank endplay. If in spec, an align bore may be in order.
 

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It will only spin when there is oil between the shaft & bearing, the action of the shaft generates a pressure (Hydrodymanic) wedge & lifts to spin freely to the only resistance which will be the shear of the oil. I.E. It will stick at first then spin freely! All white metal bearings operate this way.
 

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Discussion Starter #6
Thanks guys. An engine rebuilding friend happen to stop and concurred with what you all are saying. It seems a little stiff to start but it does rotate freely once started. I am going to finish tearing it down and just slowly go through everything. I haven't done enough motors yet to get that feel so I'll err on the side of asking...

Thanks to all.
 

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Don't quote me but i think Guy Croft, a respected Lancia twink tuner said 8 lb/ft of torque on his bottom end rebuilds.May be wrong tho.
 

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1966-2013
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Done like a resistance check in a simular fashion to setting the differential up, only using a torque wrench as opposed to the pulley thing with weights?

That's a novel approach.

What does he do if it's less than 8 lb/ft? :)
 
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