crankshaft 351w help
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bob seman
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crankshaft 351w help
i put in a rebuil crankshaft and bearings in a 351 w engine crank turns fine with mains cant turn with rods connected i'm at a lost re-manufacture crank kit
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lee_ford
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Re: crankshaft 351w help
On most motors the rods will go on the crank two rods per rod journal. They have one side tapered to provide a side surface to ride against the crank and to allow the crank to be ground without cutting too much off. If you put them on backwards the bearing will bind against the crank.
Here is a quick cross section drawing to explain. Notice the red circle. If the rod was turned around the bearing would bind against the crank.
You could have all the rods and pistons in the same holes they came out of and with flat top pistons you cannot tell which way they go easily. So look at the end connected to the crank. You may have turned one or more. Or if you have domed pistons you may have swapped hole with a couple of them. If so, then swap them back until you get them all fitting right.
Lee
Here is a quick cross section drawing to explain. Notice the red circle. If the rod was turned around the bearing would bind against the crank.
You could have all the rods and pistons in the same holes they came out of and with flat top pistons you cannot tell which way they go easily. So look at the end connected to the crank. You may have turned one or more. Or if you have domed pistons you may have swapped hole with a couple of them. If so, then swap them back until you get them all fitting right.
Lee
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My 1969 F100 Gallery
[Please note: A lot of what I write may be common knowledge to some of us. But for a new comer and even us at one time, somebody had to inform us that FIRST time.]
[Please note: A lot of what I write may be common knowledge to some of us. But for a new comer and even us at one time, somebody had to inform us that FIRST time.]
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lee_ford
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Re: crankshaft 351w help
Either that or they sent you over size rod bearings for a standard ground crank or maybe 0.020th over bearings for a 0.010th ground crank.
If all rods are turned right as noted above, then put a micrometer on the crank rod journals.
Lee
If all rods are turned right as noted above, then put a micrometer on the crank rod journals.
Lee
My 1969 F100 Gallery
[Please note: A lot of what I write may be common knowledge to some of us. But for a new comer and even us at one time, somebody had to inform us that FIRST time.]
[Please note: A lot of what I write may be common knowledge to some of us. But for a new comer and even us at one time, somebody had to inform us that FIRST time.]
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bob seman
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Re: crankshaft 351w help
the rods are 10 over the mains are 20 over mike exactly the same...... the pistons were never pulled....inital problem was two bad rod bearings.... so i check the crank and it was between 30-40 over on rods and 20 over on mains... ipick up a crank kit for 200. so i went that route
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lee_ford
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Re: crankshaft 351w help
You are replacing the crank without pulling the pistons? Please explain.bob seman wrote:... the pistons were never pulled...
Lee
My 1969 F100 Gallery
[Please note: A lot of what I write may be common knowledge to some of us. But for a new comer and even us at one time, somebody had to inform us that FIRST time.]
[Please note: A lot of what I write may be common knowledge to some of us. But for a new comer and even us at one time, somebody had to inform us that FIRST time.]
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bob seman
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Re: crankshaft 351w help
lee; thanks for helping no i didn't pull the pistons/ after taking off the end caps of the rods i just push the pistons deeper into the cylinder wall. then after carefully installing the crank with two helpers aligning the rods while i was laying the crank in place.and then installed the main caps and then the rod caps. everything line up perfectly. torgue mains to 100lbs rods to 43 lbs thanks for any input bob
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lee_ford
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Re: crankshaft 351w help
I was wondering. Six hands sounds about right to get all the rods lined up and set the crank in place.
If you used an extension to reach the nuts instead of turning the crank, then loosen them all a little until it will turn. Then tighten and check for binding one at a time.
One of your helpers may knocked a bearing off and put it on wrong. He may have done this without thinking it mattered.
When you find which rod locks the crank down, look at it closely. It may have the bearing on backwards.
Putting a bearing on wrong can compress the keeper notch. If the keeper notch is not there the bearing is more prone to spin. If you find one, you can very carefully open it back up.
I am not sure of the technical name but here is what I mean by the keeper notch. I bet that is what happened. Good luck and let me know what you find.
Lee
If you used an extension to reach the nuts instead of turning the crank, then loosen them all a little until it will turn. Then tighten and check for binding one at a time.
One of your helpers may knocked a bearing off and put it on wrong. He may have done this without thinking it mattered.
When you find which rod locks the crank down, look at it closely. It may have the bearing on backwards.
Putting a bearing on wrong can compress the keeper notch. If the keeper notch is not there the bearing is more prone to spin. If you find one, you can very carefully open it back up.
I am not sure of the technical name but here is what I mean by the keeper notch. I bet that is what happened. Good luck and let me know what you find.
Lee
You do not have the required permissions to view the files attached to this post.
My 1969 F100 Gallery
[Please note: A lot of what I write may be common knowledge to some of us. But for a new comer and even us at one time, somebody had to inform us that FIRST time.]
[Please note: A lot of what I write may be common knowledge to some of us. But for a new comer and even us at one time, somebody had to inform us that FIRST time.]
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lee_ford
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Re: crankshaft 351w help
Oh, and do not give your helpers any lip over it. Good helpers, willing to put their hands down in a motor while someone else lowers a crank in it, are hard to find.
Unless of course you did it. Then just chalk it up to experience and blame it on bad lighting or something.
Lee
Unless of course you did it. Then just chalk it up to experience and blame it on bad lighting or something.
Lee
My 1969 F100 Gallery
[Please note: A lot of what I write may be common knowledge to some of us. But for a new comer and even us at one time, somebody had to inform us that FIRST time.]
[Please note: A lot of what I write may be common knowledge to some of us. But for a new comer and even us at one time, somebody had to inform us that FIRST time.]
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fordman
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Re: crankshaft 351w help
since you say the rod bearings went bad you should have those rods checked for out of roundness first.
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bob seman
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Re: crankshaft 351w help
i took everything apart the bearings are all position correctly... but on the end caps... the rods are marked 1-8.. but the end caps are mark also but i have 3 2's 2 3s and 1-6 1-7 1-8 i believe this could be a prolem i didn't notice this when i tore in down . whats my recourse to this ... thanks bob
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lee_ford
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Re: crankshaft 351w help
What a mess. You know the answer, so before I answer, let me ask you a question. How long do I want the rebuild to last?bob seman wrote:i took everything apart the bearings are all position correctly... but on the end caps... the rods are marked 1-8.. but the end caps are mark also but i have 3 2's 2 3s and 1-6 1-7 1-8 i believe this could be a prolem i didn't notice this when i tore in down . whats my recourse to this ... thanks bob
The previous rebuilder obviously had no concern about caps and rods matching. You have seen the results. It probably caused the burned bearings. Do you want to redo this in 6 months or less? Do you want to throw the $200 Crank kit in the recycle bin? If not then do it right and buy 8 re-manufactured rods with matching caps.
The only other option I see is to pull all the rods and have a machine shop rework them.
OK, so I guess you could spend hours trying to figure out which cap fits which rod correctly and HOPE you get it right. Remember you are working with tight tolerances here. Also remember what fordman said. You will need to check them for out of round also. It would be a lot easier and better to just do it right and get all new rods.
Lee
My 1969 F100 Gallery
[Please note: A lot of what I write may be common knowledge to some of us. But for a new comer and even us at one time, somebody had to inform us that FIRST time.]
[Please note: A lot of what I write may be common knowledge to some of us. But for a new comer and even us at one time, somebody had to inform us that FIRST time.]