The Stovebolt Site Forums The Shop Area Engine Shop Bearing cap torque

To what torque should I be tightening the main bearing caps on my '54 235? The service manual is saying 35-45 ft. lbs. ( see here ). On the specification page ( link to page ), the spec is for "Oiled Threads". Why don't they just say "bearing cap bolts" or somthing more clear? What do they mean by "Oiled Threads"? Would it make a difference if the threads were clean and dry?!?

By the way, I'm not rebuilding the engine. I'm just loosening the caps in order to replace the upper rope seal which is leaking. So my plan is to simply tighten the caps back to spec when I'm done.

On a more positive note, I was pleased that my oil pan and oil pump screen looked pretty clean, more so than I would have expected!

Greg,
when you torque dry bolts there is a difference in the actual force applied due to friction.
pretty much all bearing caps, head bolts etc..call for dipping in oil before torqing em down, the oil just helps it set to the required poundage with utmost precision.
after you get your new seal in lube the threads up with some fresh oil and follow the book, you will have NP's.
Have ya ever tightened a dry bolt an heard a good SQUEEKE? the oil will prevent that and set it home as needed.
Tim

Greg,

The torque spec's you show are for the rod bearings. The manual you linked indicates 100-110 lbs for the mains. You won't fiddle with the rod bearings when you do the rear main install.

The manual is trying to tell you that torque values will be affected by how clean and easy the bolt goes into the hole. They are saying "make sure it's not rusty and cruddy" or the reading will be incorrect. "Clean and oiled" is another way of saying this...this is how Detroit engineers speak.

Stuart

Greg,

The torque values I listed above for the mains seems WAY to severe. Looking in several other books the spec's look more like 60-70 ft/lbs for these bolts. I don't know why the manual you linked shows such a ferocious value.

Stuart

Thanks guys for the responses. What you say about the threads being oiled makes total sense to me.

I'm still confused about the torque settings, though. I wasn't thinking when I references the *rod* bearing torque.. sorry for that confusion. But for the mains, 110 ft. lbs. is a lot. And Stuart has other books that say it should be about half that. Any one else know for sure?

Here is the reference to the main bearing torque setting (#4 on the left hand column)

Thanks in advance.

Greg,

I went to yet another site for a '53 engine. It too stated 100-110 ft/lbs for the mains. It almost looks like poured mains get the higher torque setting while inserted mains get the lower reading.

I'll bet someone will pop in that has been down this road before.

Stuart

In looking around I found a nice page with some of this stuff consolidated: click here

Greg,

That was one of the sites I referenced for my post....I think they are wrong on some of the data. I believe there was a post years ago mentioning that some of their specs were pasted from one year to the next and it was incorrect.

Their dope agrees with the earlier years but doesn't agree with the '55 and up engines. I 'think' this is one of those cases where you shouldn't believe everything you read on 'da net'!

I could be in left field on this, it has happened before.

Stuart

The 100-110 spec matches what the manuals I have (covering '55-'62) say.

Here's a general rule of thumb on torque values such as rod bearings, main bearings, head bolts, etc. The diameter of the bolt (NOT THE WRENCH SIZE OF THE NUT)will give you a general idea of the torque value.

3/8" bolts (most rod bolts) 30-40 ft/lbs.

7/16" bolts (Small block V-8 head and main bearing bolt size) 55-70 ft/lbs.

1/2" bolts (216/235 head bolts) 90-110 ft/lbs.

5/8" bolts ( some 3/4-ton & 1-ton wheel studs) 120-140 ft/lbs.

Threads should be clean & oiled with 30 weight motor oil. If anti-sieze or other high film strength lube is used, reduce torque by 10%.

If the main bearing bolts or studs are 1/2" diameter, usually with a 3/4" wrench size, 100 ft/lbs. is about right. 7/16" main bolts need the 55-70 ft/lb torque reading.

Jerry