Tricky Bearing Tolerance
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Joined: Aug 2003
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From: Kansas
Tricky Bearing Tolerance
Hi all, for all you for experts out there, I have a tricky question that noone can seem to answer...
I just bought my very first FORD, 1972 bronco, I bought a 351W engine from scrap yard, had it boiled and magna fluxed, bored .010 over and new water plugs, cam bearings installed.
Now, here is the tricky part, I am trying to install the crank, i finally figured out that the thrust bearing goes on the center main. Ok, laugh, I have always owned GM, anyhow, I decided to plastigauge the tolerance on the mains and rods, the crank was suppose to be ground to meet .010 over on the bearings, so i install .010 bearings, when i guage them, they journals all seem to be about .002 - .003.. Now is this a valid tolerance .? to big to small? just right?
wait there is more, this block was the year when ford was changing things between 1977 and 1978 so its a funky to find torque spec and clearances. I have many telling me to torgue the mains at 95-105 ft-lbs is that right? rods at 45 ft-lbs
no one in my town has been able to run the block numbers to give me accurate information. Please help if you can, I would very much appreciate it, its been sitting in my garage for 3 weeks now because i cant find the specs...
~M
I just bought my very first FORD, 1972 bronco, I bought a 351W engine from scrap yard, had it boiled and magna fluxed, bored .010 over and new water plugs, cam bearings installed.
Now, here is the tricky part, I am trying to install the crank, i finally figured out that the thrust bearing goes on the center main. Ok, laugh, I have always owned GM, anyhow, I decided to plastigauge the tolerance on the mains and rods, the crank was suppose to be ground to meet .010 over on the bearings, so i install .010 bearings, when i guage them, they journals all seem to be about .002 - .003.. Now is this a valid tolerance .? to big to small? just right?
wait there is more, this block was the year when ford was changing things between 1977 and 1978 so its a funky to find torque spec and clearances. I have many telling me to torgue the mains at 95-105 ft-lbs is that right? rods at 45 ft-lbs
no one in my town has been able to run the block numbers to give me accurate information. Please help if you can, I would very much appreciate it, its been sitting in my garage for 3 weeks now because i cant find the specs...
~M
Posting Guru
Joined: Jan 2003
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From: Still under the hood in O
Tricky Bearing Tolerance
Welcome to FTE!!
What is this motor out of?
The clearances I have for a 73-79 351W car motor is .0013-.0030 with a side note for 74-77 which were .0008-.0025 . And .008-.0015 on a 78 truck motor (77 didn't have the 351W for the truck, only the 351M)
I think your safe on that. If you want extra insurance just add a HV oil pump.
As far as torque specs - I only have the 74-79 351W which is 95-105 with no side notes, so I would say this is safe.
The rod bolts are 40-45.
Good luck!
What is this motor out of?
The clearances I have for a 73-79 351W car motor is .0013-.0030 with a side note for 74-77 which were .0008-.0025 . And .008-.0015 on a 78 truck motor (77 didn't have the 351W for the truck, only the 351M)
I think your safe on that. If you want extra insurance just add a HV oil pump.
As far as torque specs - I only have the 74-79 351W which is 95-105 with no side notes, so I would say this is safe.
The rod bolts are 40-45.
Good luck!
Tuned
Joined: Jun 2003
Posts: 307
Likes: 1
From: South Florida
Tricky Bearing Tolerance
Jikester, an interesting sidenote.
I had a 78 ford van I bought new with a 351 and at the time I ordered the factory manuals from Ford. I think there were 4 or 5 of them total. When it came time to rebuild the engine I locked up the crank torque specs and stretched every bolt. These were the original bolts. I had to order new bolts from Ford. I then found out that the specs in their manual were wrong. I seem to remember I stretched them at around 95 and the real spec ended up being around 75. That was almost 20 years ago but it was the first and only time it ever happened. So now I double check numerous sources to be safe.
I had a 78 ford van I bought new with a 351 and at the time I ordered the factory manuals from Ford. I think there were 4 or 5 of them total. When it came time to rebuild the engine I locked up the crank torque specs and stretched every bolt. These were the original bolts. I had to order new bolts from Ford. I then found out that the specs in their manual were wrong. I seem to remember I stretched them at around 95 and the real spec ended up being around 75. That was almost 20 years ago but it was the first and only time it ever happened. So now I double check numerous sources to be safe.
