Manual Torque Specs Wrong

onenationundergoat · 08-29-2015, 05:48 PM

I'm pretty much overhauling my engine. When we went to torque the connecting rod bolts, the manual said to go to 130ft. lbs. That seemed like a lot for these lil bolts, but the manual mentioned this spec many times.

Started torquing, bolt started stretching. It might be too late and we might have to remove the head again to replace the connecting rod bolts. UGH.

Looked online, and according to agkits specs the torque is 80 ft. lbs!

On my DT360 the connecting rod bearings meet horizontally parallel to the floor. In the manual they are diagonal. Does anyone else know which way the rods are on their DT360? I'm wondering if someone in the past replaced the connecting rods with a different style.

bluebird90 · 08-29-2015, 06:31 PM

You do NOT need to remove the head. just drive out 1 bolt at a time with the piston at BDC.

onenationundergoat · 08-29-2015, 07:36 PM

Since only one set of bolts was over tightened, we counted how many times the nut had to spin to get to 80 ft lbs on one of the not-yet-tightened rod bolts. Then we took the overtightened one loose and counted how many times the nut spun around to get it back to 80. They ended up being the same, so we're gonna say the bolt wasn't stretched much. So we're just gonna leave it as is.

Thanks for the info, though! It was a very scary thought after all the work putting this back together.

sdwarf36 · 08-29-2015, 08:51 PM

Do NOT reuse the bolt!!!!! The amount of bolt stretch is what makes the clamping force-not how "tight" something is. If the bolt has stretched any more than was engineered in, its junk.
I built race engines professionally for many years. All the rod bolts are torqued + measured for overall stretch. The stretch number is more importiant that the amount of torque on the wrench getting there. ( a quote from ARP-maker of the rod bolts- "I don't care if you use a monkey wrench + peanut butter as lube-the only thing that matters is the stretch number.") On serious engine builds, you log the length of the bolt + keep track of it. Replacement needed if they gain .002. If you went over spec by 50 lbs., you might have tweeked it.
As said before- you dont have to pull the head-just the pan+ turn the crank to a good position. For the couple of buck a rod bolt would cost, I wouldn't risk it.

somewhereinusa · 08-29-2015, 10:54 PM

What he said, do not re use an over tightened rod bolt. Even if there is the slightest question it is junk.

onenationundergoat · 08-30-2015, 12:49 AM

Yeah we've since decided to replace it. Any idea where we can find rod bolts without having to order them? We're hoping to have it all back together and running tomorrow. All that's left is the exhaust manifold and oil pan, besides replacing those two rod bolts.

EastCoastCB · 08-30-2015, 06:40 AM

Quote:

Originally Posted by onenationundergoat

Yeah we've since decided to replace it. Any idea where we can find rod bolts without having to order them? We're hoping to have it all back together and running tomorrow. All that's left is the exhaust manifold and oil pan, besides replacing those two rod bolts.

Wishing yall the best!

I just last night snapped an exhaust stud off on my scooter. I guess I don't know my own strength!
Now the FUN begins...

claydbal · 08-30-2015, 07:24 AM

goat dude, you really should find a mechanic to help you. when rebuilding an engine, rods are torqued before head is installed.

EastCoastCB · 08-30-2015, 07:37 AM

Quote:

Originally Posted by claydbal

goat dude, you really should find a mechanic to help you. when rebuilding an engine, rods are torqued before head is installed.

Wow... you are just one big ray of sunshine aren't you...

BlackJohn · 08-30-2015, 09:46 AM

The 11th commandment

An over-torqued bolt is already half broke!

onenationundergoat · 08-30-2015, 10:49 AM

We did that before the head was torqued, it was just set in place and the bolts were in finger tight. The rod bolts were tightened but not torqued to spec at that point. Then when the first set of rod bolts let us know that something was wrong we checked and used the correct torque on the rest. Then after that torqued the head bolts. My dad has rebuilt engines for thirty years or more, just not diesels, so this is a little bit different but not too much.

I just can't get over how wrong the manual was. I wonder how many other people have had the same (or worse) experience.

EastCoastCB · 08-30-2015, 01:06 PM

Quote:

Originally Posted by onenationundergoat

We did that before the head was torqued, it was just set in place and the bolts were in finger tight. The rod bolts were tightened but not torqued to spec at that point. Then when the first set of rod bolts let us know that something was wrong we checked and used the correct torque on the rest. Then after that torqued the head bolts. My dad has rebuilt engines for thirty years or more, just not diesels, so this is a little bit different but not too much.

I just can't get over how wrong the manual was. I wonder how many other people have had the same (or worse) experience.

Manuals are a good start but yeah they often have odd errors.
Good thing you caught it.
I usually get something nearly assembled and realize I have to tear it back apart, too. Happens all the time.

claydbal · 09-01-2015, 06:18 AM

Quote:

Originally Posted by EastCoastCB

Wow... you are just one big ray of sunshine aren't you...

i reckon, if thats what you call trying to help. care to clarify?

Scooternj · 09-01-2015, 06:54 AM

Quote:

Originally Posted by EastCoastCB

Manuals are a good start but yeah they often have odd errors.

Agreed, having been a technical publications manual custodian with the Guard, and required to use them for literally *everything*. That being said, they're also *not* "real world." They're god for a start, and a checklist, but when real world experience kicks in, they sometimes go out the window.

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