Working on my D3B with the 3204. Manual says to torque Mains to 45 FTLB and Rods to 30 FTLB. Once torqued you mark the bolt then tighten further an additional 60 degrees +/- 5 degrees. The issue is I'm seeing Rods final torque being anywhere between 48 to 60 FTLB on Rods. There are also differences on Main bearings. I can tell this by using a beam torque wrench. The main bolts I think are 1/2 inch with a 7/8 inch head. The Rods are 7/16 x 20 bolt and nut. Thinking I should just torque them to a number instead of a degree. Also I'm using ARP torque lube
The manufacturer is after a defined amount of bolt stretch, which is why you turn 60 degrees. The variation in the torque required to get that bolt stretch is EXACTLY the reason why you can't just torque them to a specific torque, the actual clamping load on the bolt head would be all over the place.
OK thanks I'll take your word for it. Sure is puzzling that you can get the same amount of stretch and the actual torque varies 15 FTLB. Think I'll loosen them all up one more time and try again (already done it twice.
Yair . . . AllDodge . Dunno mate, I have been out of the game a long time but it used to be that some bolts in such an application should only be taken up to toque and stretched once, in other words they may not be reusable . . . I could be talking bull ****e but I would get some advise from the dealer or watch this space . . . if I am talking out of place some one will shoot me down in flames. If I was working on that engine a couple of hundred bucks or what ever for a new set of bolts would be worth it for peace of mind. Cheers.
I hear what your saying and would agree if they were over stretched, but CAT has always said you can rebuild their engines many times. I did check all the bolts prior to install under magnification (no a whole lot) and found nothing to give me concern. In all the CAT manuals I have none mention about replacing the bolts. On a note, the third time was the charm. Rods all came in around 60 FTLB and mains came in around 145 FTLB. Maybe there was a slight bur or something. Would like to find a clearance spec for the head. New pistons stick up above the block deck (working from memory) about .060 and the new gasket is about .075. Not a whole lot or room for error
Yair . . . AllDodge . Good one mate, as long as you are aware . . . it seems that sort piston clearance sure don't leave much room for carbon but I know nothing about modern engines . . . and not a lot about the old ones as far as that goes. (big grin) Cheers.
Stay true to the book
So the rods that were at 48 ft lbs after stretching and now are at 60 ft lbs, did they turn more after the re-torque? Or is your 60 degree mark still bang on ?
Puts teachers hat on .............. As someone mentione above, the whole idea of "torque-turn" is to get a consistent tension or clamping force in a bolted joint, whatever the joint might be. In your case it's your main bearing and rod bearing caps, but it could be anything. Most times it's so the bolt can be loaded to a tension very close to its elastic limit, bolts tightened like this have ONE LIFE ONLY and should be replaced every time the joint is disassembled. Generally in engine fasteners though the intention is to simply get a consistent clamping force, the bolts can be reused as many time as you like so long as they comply with reusability guidelines that cover things like corrosion, thread damage, nicks, burrs, etc. The problem is that when your torque wrench (when was it last calibrated if I can just throw that in at this point) simply measures the resistance to turning. Now that resistance is made up of the tension in the bolt but also as the bolt gets tighter a lot of the "torque" is actually friction in the threaded fastener itself, nothing to do with the clamping force. So fasteners that are not in perfect condition under bolt heads or nuts, or washers, or a damaged thread (as just a few examples) can give you a completely false - usually too low - tension in the bolt despite the fact that your "recently-calibrated" torque wrench clicked off bang on the set torque. If our guys are using a torque wrench on anything when they collect it from the tool store they have put it on the meter to check the calibration before using it. Every time - no exceptions. Anyhoo, back to torque-turn. It's a simple mathematical calculation to figure out the tension applied on a bolt by turning it 60, 90, 120 degrees, or whatever because of the thread pitch. So the process is basically to apply a fairly low torque initially to get the joint to "seat", then you go back and put the degrees on it which is what actually puts the tension in the fastener. In the case of your engine if you have no idea how many times it's been down before and unless you are 100% sure the bolts are good, I personally would replace them, but then again I'm not looking at them. Are you using a beam or click-type torque wrench to tighten the bolts..? My preference would be for a click-type, the only time I would normally use a beam-type is for setting rolling torque on bearings.
Yair . . . Good one Nige . I would be interested to see you comment on the wheel studs thread. I seem to remember 71 series two strokes were one use only on big ends and mains? Could be wrong. On some of the large engines, English Electric, Blackstone and so on the bolts (three quarter or inch) were miked for length and then miked for stretch to a predetermined value . . . just six foot of pipe on a one inch ratchet no torque wrench needed. SAE 30 oil was specified for lubricating faces and threads. Cheers.
Each time I was spot on with the mark and only watched the torque. Something must have been in a the threads. Don't see how something could have been there, looked, cleaned, wire brushed holes, guess I should have tap chased the threads. Next time. I would like to get my torque wrench re-calibrated, but no it never has been. Think about it now and then just never had it done. I have Seven torque wrench's of different sizes. When torqueing the bolts in this thread I used a beam wrench so I could see where it was when I reached the 60 mark (reason for the thread). If I'm going for a straight torque number I use a clicker, and also keep the wrench unwound when not being used. Thanks all for the help, and sure hope I didn't mess up by not replacing the bolts Only torque wrench I still want is a deflecting beam wrench. Would be better when torqueing the wheel studs on my dump truck IMO
Personally I'd use a click-type wrench to set the initial torque on a torque-turn fastener, then a simple cheater bar (with or without pipe) to put the degrees on the bolt/nut/whatever. You don't need to use any type of torque tooling to put the degrees on after the initial torque, just a big bar and have at 'er .......... Take something like the bolts that fix a 994 diff housing to the frame - 1600ft.lbs. + 90 degrees. That's a hydraulic wrench job ......... Scrub - which thread were you talking about regarding wheel studs. Did I miss something..?
Scrub, I do 71series Detroits all the time and Ive never had to replace rod or main bolts unless they had an obvious issue. 60 us lb ft on a 7/16 inch rod bolt isnt torque to yield, nor is 200 lb ft on a 5/8 inch main bolt. No disrespect. just saying. Actually the old 71s have pretty generous specs.
Correct - you don't need to be too concerned about the torque required to rotate the bolt after applying the initial torque, just the clamping force that the bolt is exerting on the joint. That's what the 60-degrees does. The difference in torque that you measured from one bolt to another could be something as simple as a burr on a bolt head or a washer, or on a thread of the bolt.