[gprocket]

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

 

[Tifosi]

Last actual reference to that I saw was that once given a healthy spin, it should make 2 rotations before it comes to a stop. (Jim K. DOHC Alfa performance manual)

 

[PSk]

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

 

[papajam]

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.

 

[crashmctavish]

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.

 

[gprocket]

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.

 

[strat24v]

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.

 

[Tifosi]

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?

 

[gprocket]

Tighten the bolts

 

[Tifosi]

Somehow I'm guessing that won't do it

 

[schuga]

Bringing back an old post.

Building a 1600 engine and have the crank in and it turns freely at 36 ft/lbs (w/o oil) for 'preassembly'. Followed Jim K's advice as in his book, tightened down in stages and it spins nicely at all torque steps.

However maybe Jim K has Steve Garvey forearms or massive biceps, but I cannot get the crank to spin two rotations, no matter how hard I try.

I do have a good coating of Ultra Slick and that is probably causing some slight 'good' resistance, So I am wondering if 'spins nicely' and easily by hand is acceptable?

Chip

 

[Alfajay]

Building a 1600 engine and have the crank in and it turns freely at 36 ft/lbs (w/o oil) for 'preassembly'. I do have a good coating of Ultra Slick and that is probably causing some slight 'good' resistance,

Hmm. My experience matches what Psk and Papajam wrote in posts #3 & 4 in this thread: crank alone can be spun by hand, but it takes a wrench once pistons & rings installed. 36 fl-lbs is a whole lot more than I could generate by hand and alone seems like a lot just to turn the crankshaft alone. I don't know what Ultra Slick is like - maybe it's thick enough to cause that.

 

[schuga]

Let me clarify. The crank spins freely by hand when the main caps are torqued to 36 lbs (w/o oil).

Ultra slick is engine assembly lube and quite tacky.

 

[Alfajay]

Let me clarify. The crank spins freely by hand when the main caps are torqued to 36 lbs (w/o oil).

Sorry, I misunderstood what you were applying the 36 ft-lbs to. I'm sure your bearings and crankshaft are fine. No one could spin a crankshaft fast enough by hand to get it to spin a couple of turns with a sticky lubricant.

 

[ITALCAROZ]

I had trouble spinning mine freely and went back to the machinist, he told me to torque up the mains and check again and he presto it turned freely. apparently the bearings aren't the correct shape until torqued down sort of oval.

 

[schuga]

Thanks all who have responded.

I am still confused about what the bearing clearances should be (1600 engine) as I have read various opinions ranging from .001 - .0025 on the BB.

I am trying to build a performance street engine (Spruell 1600>1700 pistons, larger intake, and exhaust valves, high-perf valve springs, rebuilt oil [by Gordon Raymond], new timing chains, but have yet to select the cams [probably RJ cams]).

Mains and bearing clearances were measured by a reputable machine shop in indy (thanks Gordon via research in the BB). All mains were torqued to 35 lbs, except #5 which was taken to 38 lbs to get into range. I am running .010 King bearings with std thrust washers.
#1 - Block main bearing bore w/bearing is 2.3528=A, crank main journal measures at 2.3507=B, resulting in a bearing clearance of .0021" @ 35 lbs = C (Equation: A-B=C)
#2 - Block main bearing bore w/bearing is 2.3530=A, crank main journal measures at 2.3507=B, resulting in a bearing clearance of .0023" @ 35 lbs = C
#3 - Block main bearing bore w/bearing is 2.3529=A, crank main journal measures at 2.3505=B, resulting in a bearing clearance of .0024" @ 35 lbs = C
#4 - Block main bearing bore w/bearing is 2.3529=A, crank main journal measures at 2.3506=B, resulting in a bearing clearance of. 0023" @ 35 lbs = C
#5 - Block main bearing bore w/bearing is 2.3539 @ 35 lbs and (2.3532 @ 38lbs=A), Main journal measures at 2.3507=B, resulting in a bearing clearance of .0025" @ 38 lbs (.003-.0032" @ 35 lbs) = C

Please let me know if I need to clarify the information listed above as I have done my best to detail it in a simple way as I am no engineer.

Guidance would be great and appreciate keeping points, well on point.

Thank you in advance.

Chip

 

[goats]

I;d suggest you plastigauge the actual running clearances. Losing (usually) a couple tenths due to bearing positioning, minor cap anomalies, etc is not unusual. Plastigauge will give you the real clearances, I like to do both bottom and top.

 

[gigem75]

I was also going to suggest plastigauge. That will tell you for sure. I have used Lubriplate Motor Assembly grease
Lubriplate L0034-094 No. 105 Motor Assembly Grease, 10 oz
for 50 years and there is a little initial resistance and then easy turn with one hand at the rod journal. With flywheel on super easy at the flywheel but a little more resistance at the crank.

 

[schuga]

Thanks all. I will post measurements and pics soon.