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Engine rebuild, help!
#1
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moodydavid16
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I have a 1948 super eight sedan that I am currently rebuilding the engine for. I am currently trying to reinstall the crankshaft. however whenever I put the main caps on and tighten them the crankshaft binds and wont turn without excessive force. I have determined that it is only the 2 closest to the transmission side that bind (I have the engine with 5 mains) I have checked the clearances and they all check out. the only work I have had done is I had a machine shop grind the crank down .010" on both main and rods. I have bought the same oversize bearings from kanter (.010") as well. i also have plenty of assembly lube on everything. does anyone have any ideas as to what might be going on? also, i find that when the caps are off and i turn the engine it will make a clunk sound when it gets to the same point as where i had initially torqued down the caps and found it would bind. not sure if this is related or even an issue.

Posted on: 12/4 19:50
"You're not having fun unless someone gets hurt or the cops show up"
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Re: Engine rebuild, help!
#2
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HH56
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Any chance the bearing caps got switched or did you swap one from another engine and the block needs to be line bored? You said the clearances were OK in the offending spots but is there any chance perhaps a wrong bearing half shell somehow got put in a box or mixed in the set? Is there any kind of debris under a bearing shell that would act as a shim? No suggestions as to the clunk other than possibly endplay is excessive and crank is shifting while you turn it or to look carefully and see if a counterweight has any new shiny spots from hitting something. If the oil fill tube is inserted incorrectly a counterweight can hit the baffle but think that would be a more metallic tinny sound rather than a clunk.

Posted on: 12/4 20:11
Howard
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Re: Engine rebuild, help!
#3
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Owen_Dyneto
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Have the crankshaft checked for straightness.

Posted on: 12/4 21:07
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Re: Engine rebuild, help!
#4
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moodydavid16
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will do

Posted on: 12/4 22:52
"You're not having fun unless someone gets hurt or the cops show up"
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Re: Engine rebuild, help!
#5
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moodydavid16
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Any chance the bearing caps got switched or did you swap one from another engine and the block needs to be line bored?
I am still using the same caps from the original block and I am sure they are in the same order as when disassembled
You said the clearances were OK in the offending spots but is there any chance perhaps a wrong bearing half shell somehow got put in a box or mixed in the set?
they each came in separate packaging as pairs and are all different widths so in short no they cant possibly be mixed up
Is there any kind of debris under a bearing shell that would act as a shim? I believe I got them pretty dang clean but I will definitely go back and re clean them- thanks for the sugggestion.
No suggestions as to the clunk other than possibly endplay is excessive and crank is shifting while you turn it or to look carefully and see if a counterweight has any new shiny spots from hitting something. If the oil fill tube is inserted incorrectly a counterweight can hit the baffle but think that would be a more metallic tinny sound rather than a clunk.
I have a bare block so its not hitting anything, but it is possible that it has excessive endplay.

Posted on: 12/4 23:00
"You're not having fun unless someone gets hurt or the cops show up"
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Re: Engine rebuild, help!
#6
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Ozstatman
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Agree with what O_D said. Had a mate who rebuilt his '37 SuperEight engine and experienced the same thing. The crankshaft wouldn't rotate after the rebuild, all the main and rod bearing journals had been ground and new proper-sized bearings installed. Backing off the torqued down caps did allow it to rotate. Turns out the crankshaft was "bent"! Used to work before the rebuild, but not after. I guess the clearances on all the bearings before rebuild was such that there was sufficient clearance to allow the bent crankshaft to rotate and run. Reason he rebuilt the engine was the particles of bearing found during an oil change! Unlikely to be a bent crankshaft, but you never know.

Posted on: 12/4 23:54
Mal
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====

Bowral, Southern Highlands of NSW, Australia
"Out of chaos comes order" - Nietzsche.

1938 Eight Touring Sedan - SOLD

1941 One-Twenty Club Coupe - SOLD

1948 Super Eight Limo, chassis RHD - SOLD

1950 Eight Touring Sedan - SOLD

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Re: Engine rebuild, help!
#7
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Wat_Tyler
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A bent crank was the first thought that entered my mind. It can happen . . . .

Posted on: 12/5 6:50
If you're not having fun, maybe it's your own damned fault.
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Re: Engine rebuild, help!
#8
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Ross
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The new rope seal at the back of the crank can make a hellacious drag and I often have to bring the rear cap down bit by bit while rotating the crank to burnish it. I don't put the other caps on til that is accomplished.

End play is determined by the center main and is fixed unless your crank grinder made a boo boo.

Posted on: 12/5 7:25
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Re: Engine rebuild, help!
#9
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JeromeSolberg
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IIRC I was quite surprised at how hard it was to turn the crank when I first installed the rope seal, as mentioned below. The rope seals are weird things for someone not used to them, as I was not.

There is an issue with the oil fill/breather tube, if it is installed backwards it can hit the crank, that might be issue with the "clunk". That's an easy fix just pull it out and turn it 180 degrees and push it back in.

Posted on: 12/5 10:53
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Re: Engine rebuild, help!
#10
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moodydavid16
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IIRC I was quite surprised at how hard it was to turn the crank when I first installed the rope seal, as mentioned below. The rope seals are weird things for someone not used to them, as I was not.
I will try taking them out and seeing if there still is a problem
also the oil tube is not installed

Posted on: 12/5 18:56
"You're not having fun unless someone gets hurt or the cops show up"
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