390 crank not round
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Fleet Owner
Joined: Jun 1999
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From: Creedmoor, North Carolina
390 crank not round
We have a new crank kit in a 390 rebuild, and with one piston connected, tested the rotation drag with a dial torque wrench. I get from 10 lbs to 22lbs around the revolution when starting from a stand still. I feel it should be closer to the same all around. My other engine was about 5-7lbs in total.
What is the thoughts from you engine builders? Am I overly concerned or is this OK to install?
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John
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In the cool still quiet of night, you can hear chevies rusting away.
What is the thoughts from you engine builders? Am I overly concerned or is this OK to install?
http://www.clubfte.com/users/jowilker/USFlag.gif
John
jowilker email me
[link:www.ford-trucks.com/users/jowilker|My Club FTE Page] Member since 01 01
[link:www.ford-trucks.net/users/jowilker/NCFTE.html|NCFTO] North Carolina Ford Truck Owners Group
In the cool still quiet of night, you can hear chevies rusting away.
Senior User
Joined: Feb 2002
Posts: 465
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390 crank not round
i havent built engines,but having more pistons conected
would make the rotation smoother rather than a rough
up down resistence being felt.thats my 2 cents ,just a
thought,I ve only taken motors apart
Fe power
would make the rotation smoother rather than a rough
up down resistence being felt.thats my 2 cents ,just a
thought,I ve only taken motors apart
Fe power
Senior User
Joined: Jul 2001
Posts: 298
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From: Oztralia
390 crank not round
>We have a new crank kit in a 390 rebuild, and with one
>piston connected, tested the rotation drag with a dial
>torque wrench. I get from 10 lbs to 22lbs around the
>revolution when starting from a stand still. I feel it
>should be closer to the same all around.
This is a very unusual test indeed.
Does the piston have rings on ?
What sort of seal does it have ?
What sort of oil did you assemble it with.
This test is unlikely to give any indication of the "roundness" of the crank shaft, that can only be assertained with micrometers.
Palstigauge, will give you the difference in diameter at the point you measured.
I would suggest you are measuring ring drag and the experinecing the effect of changing piston speed that a reciprocating engine endures. Also at the speeds you are turning it you only have hydro-static/ boundary lubrication and no hydro dynamic.
My other engine was
>about 5-7lbs in total.
>
>What is the thoughts from you engine builders? Am I overly
>concerned or is this OK to install?
over stating my thoughts :- why are you emailling and not finishing the assembly.
>piston connected, tested the rotation drag with a dial
>torque wrench. I get from 10 lbs to 22lbs around the
>revolution when starting from a stand still. I feel it
>should be closer to the same all around.
This is a very unusual test indeed.
Does the piston have rings on ?
What sort of seal does it have ?
What sort of oil did you assemble it with.
This test is unlikely to give any indication of the "roundness" of the crank shaft, that can only be assertained with micrometers.
Palstigauge, will give you the difference in diameter at the point you measured.
I would suggest you are measuring ring drag and the experinecing the effect of changing piston speed that a reciprocating engine endures. Also at the speeds you are turning it you only have hydro-static/ boundary lubrication and no hydro dynamic.
My other engine was
>about 5-7lbs in total.
>
>What is the thoughts from you engine builders? Am I overly
>concerned or is this OK to install?
over stating my thoughts :- why are you emailling and not finishing the assembly.
Thread Starter
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Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
390 crank not round
Email from partner
Crank was poorly ground, egg shaped on the number two journal. Bill
put it his lathe and fixed it. Everything else was OK.
90 in-lbs to start rotation, 25 or so to maintain rotation. Was 25 ft-pounds or 300 in-lbs to start as you recall.
Starting on the timing gears then pistons in a few minutes. Should have it close to done this evening.
Thanks for the replies fellows.
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John
jowilker email me
[link:www.ford-trucks.com/users/jowilker|My Club FTE Page] Member since 01 01
[link:www.ford-trucks.net/users/jowilker/NCFTE.html|NCFTO] North Carolina Ford Truck Owners Group
In the cool still quiet of night, you can hear chevies rusting away.
Crank was poorly ground, egg shaped on the number two journal. Bill
put it his lathe and fixed it. Everything else was OK.
90 in-lbs to start rotation, 25 or so to maintain rotation. Was 25 ft-pounds or 300 in-lbs to start as you recall.
Starting on the timing gears then pistons in a few minutes. Should have it close to done this evening.
Thanks for the replies fellows.
http://www.clubfte.com/users/jowilker/USFlag.gif
John
jowilker email me
[link:www.ford-trucks.com/users/jowilker|My Club FTE Page] Member since 01 01
[link:www.ford-trucks.net/users/jowilker/NCFTE.html|NCFTO] North Carolina Ford Truck Owners Group
In the cool still quiet of night, you can hear chevies rusting away.
Senior User
Joined: Jul 2001
Posts: 298
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From: Oztralia
390 crank not round
[updated:LAST EDITED ON 18-Jun-02 AT 11:06 PM (EST)]I was a little confused by the open post
Now I'm bamboozled.
The number 2 crank pin was out of round ? ( or was it a main)
How far ?
How did you get the surface finish by turning it in a lathe
How did you balance the lathe to turn the crank.
Can ya give a "full" rundown on this little saga
Now I'm bamboozled.
The number 2 crank pin was out of round ? ( or was it a main)
How far ?
How did you get the surface finish by turning it in a lathe
How did you balance the lathe to turn the crank.
Can ya give a "full" rundown on this little saga
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Thread Starter
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Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
390 crank not round
Wayne, Bob took it back to the machine shop where he bought the crank kit from. After a lot of checking of the journals, one was found to be out of round. I posted what he sent me, but they don't know how it could happen. This shop can grind cranks, we had to buy one because of a 360 to 390 upgrade.
Bob is recording the drag on the crank as each piston is added. Don't ask, I don't know why, but the engine is better off now. IMHO
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John
jowilker email me
[link:www.ford-trucks.com/users/jowilker|My Club FTE Page] Member since 01 01
[link:www.ford-trucks.net/users/jowilker/NCFTE.html|NCFTO] North Carolina Ford Truck Owners Group
In the cool still quiet of night, you can hear chevies rusting away.
Bob is recording the drag on the crank as each piston is added. Don't ask, I don't know why, but the engine is better off now. IMHO
http://www.clubfte.com/users/jowilker/USFlag.gif
John
jowilker email me
[link:www.ford-trucks.com/users/jowilker|My Club FTE Page] Member since 01 01
[link:www.ford-trucks.net/users/jowilker/NCFTE.html|NCFTO] North Carolina Ford Truck Owners Group
In the cool still quiet of night, you can hear chevies rusting away.
Senior User
Joined: Jul 2001
Posts: 298
Likes: 0
From: Oztralia
390 crank not round
OK so it was a crank pin (not a main).
I guess i always did by "feel" the test that is being done as I installed each piston.
But I always measured and checked clearance and roundness with a mic.
Out of round crank grinds are usually the result of "tired" or poorly setup (balanced) grinders.
It is good to understand
I guess i always did by "feel" the test that is being done as I installed each piston.
But I always measured and checked clearance and roundness with a mic.
Out of round crank grinds are usually the result of "tired" or poorly setup (balanced) grinders.
It is good to understand
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