What are the consequences of overtorquing?

[700rpm]

I read that mains should be torqued between 80 and 90 ft-lbs., but I have had to go to 100 sometimes to get the castles aligned. The crank still turns by hand at this point. So what are the potential problems?

[John Duden]

Breaking, striping, stretching bolts and threads. Some makes of engines only prefer one use of a bolt or nut since thes stretch or get heat treated and get brittle.
John

[700rpm]

Good points, John. Thanks. I haven't experienced those, but I'll keep,them in mind in the future.

[Drive Shaft Dave]

An old time Model A Mechanic friend of mine , once told me , get the main's tightened up as much as you can get them. Probably 80 -90 Ft Lbs. God Bless you Walt.

[shamer]

Bolts typically have torque values of 60 to 80 percent of their yield values. With that in mind and assuming your bolts were in good condition and your torque wrench was calibrated, I wouldn't worry about them. If you wanted to ease your mind, you could remove and measure their length to insure they're all the same and that none are stretched.

Steve

[hardtimes]

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Originally Posted by shamer

Bolts typically have torque values of 60 to 80 percent of their yield values. With that in mind and assuming your bolts were in good condition and your torque wrench was calibrated, I wouldn't worry about them. If you wanted to ease your mind, you could remove and measure their length to insure they're all the same and that none are stretched.

Steve

Hey Steve,
'remove and measure'. I was just at an engine building shop that specializes in racing engines, but does all kinds of engines including As/Bs.
The head assembler showed me how they use measurement instruments to calibrate yield of fasteners used. He stated that they use the fasteners ONCE, but check for yield to ensure proper torque.
Also, I've got a Model A /B parts supplier book that states that the main bolt torque should be 120 lbs !

[KMeredith87]

In the aircraft world when you torque a bolt we start at the lowest setting to get the castle to align and work up to the highest setting. If we reach the highest setting and still cannot get it aligned the nut is then removed discarded and replaced with a different one and never over torqued. Now aircraft are a little more precise as there is no where to pull over at 35,000 feet but after years of working in them I apply these same rules to my engines.

[Arlyn Bieber]

Unless you are going for judging, use lock washers. With 80 ft-lbs of torque and a lock washer they won't come loose.

[tbirdtbird]

You are stretching the bolts and all the threads beyond their design and will loose clamping force and the assembly will fail when you least expect.

If the cotter windows don't line up at the specified torque the best procedure is to remove the nut, and grind slightly and carefully on the side of a grinding wheel.

I grind slightly in 3 stages: I rotate the nut 120* between each touch to the grinding wheel. This equalizes any slight mis-match in angle that I may have to the wheel. We have done it so much in this shop I can do it in my sleep. Take any old 1/2 inch nut you have laying around, and practice. Use your dial caliper to check for trueness when done and see how close you are. It is way easier than you think

[shamer]

There has been some good info offered by guys who seem to have a good understanding of these particular engines. I would just clarify my original post by saying that all fasteners stretch when torqued and measuring the stretch is the best way to insure proper torque. But how many of us working in our garage who build an occasional engine can justify anything other than a torque wrench?
A bolt that "stays stretched" when removed has exceeded its yield strength and should be discarded.
If the torque spec for the original posters situation is in fact 120, then he definitely has no problem.

[Patrick L.]

There are few areas where a torque wrench is needed as long as one has some calibration in their elbow.
That said, I think that a main bearing retainer is a good place for one. On a castle nut such as ours, once I hit the starting tonnage [ say 80 lb-ft] and there is quite a bit of room left to get the holes to line up which I think would cause it going beyond say 90 lb-ft, then I sand the retaining nut a bit.
Plus, I see folks use torque wrenches incorrectly quite often and just cringe when I see it.
But, all this said, if it tightened up nicely for you and didn't start to get 'mushy' [technical term, smiley face] then you should be fine. An extra 10# shouldn't hurt a thing.

[shamer]

[QUOTE=1930 coupe;946862]Most torque values are the maxim before the bolt strips or breaks,

With all due respect, this is bad information.

[Chuck Sea/Tac]

Do you even need lock washers if you don't use cotter pins? I can't see how they would loosen up. I know on the rods a non castle nut with a pal nut works fine.