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Sun Nov 06, 2016 5:24 pm

I've just tightened a set of CB race rods with 5/16 ARP 2000 bolts. I tightened them to the 29 ft/lbs spec, and then checked stretch. On average, my bolt stretch at that torque is .0035", one is as low as .0027". The stretch spec is .0048-.0052"
So, is that maximum stretch before failure? My understanding is that the bolt is strongest when torqued to the max stretch, right?
Given this scenario, which is the better option?
1. Tighten them all to the same torque and call it a day
2. Torque the lesser stretched bolts so that they match the others
3. Torque them all to the max stretch listed by ARP

On this particular engine its a moot point, as it'll lead an easy life shoving an old bus around. I'm sure leaving them torqued to 29 is fine for this. But, when building with nice components I like to get as much as close to perfect as I am able.
SD

Sun Nov 06, 2016 5:48 pm

Did you torque "wet"? (Oiled) Stretch is the most accurate way to torque fasteners.

Sun Nov 06, 2016 5:54 pm

I'd be phoning ARP tomorrow morning and asking them.

Sun Nov 06, 2016 5:56 pm

Ace wrote: Did you torque "wet"? (Oiled) Stretch is the most accurate way to torque fasteners.
Yes, with the ARP lube, and a recently calibrated torque wrench.

Sun Nov 06, 2016 6:12 pm

I'd use oil, find the torque to stretch .004 on two experimentally, and go with that on all of them.
Those rods were torqued and honed at CB, and you KNOW they did not stretch them to the max, and you probably don't need to either, could cause more problems than it would solve if any. Or, moderation in all things :D

but if you already applied the moly lube, stick with it. It's hard to Un-apply it.

Sun Nov 06, 2016 6:32 pm

Seems like a few years ago the spec said "do not exceed X stretch" I think we over think everything these days. I check stretch on all mine, but I'm mainly checking for dud bolts.

Sun Nov 06, 2016 7:19 pm

you need to make sure the threads in the rod are perfectly clean then oil or use the lube and they need to be torqued atleast 2 times, I like 3 times, but 2 works. and be sure to have lube on your face of your nuts :shock: the rod serface too as well as in the nuts.(nuts or bolts, they need lube on the face that contacts the rod and in the threads in the rod. like in somebodys sig like....never screw a dry hole....and remember by the time you bottom out there aint much lube on the end..thus add some lube in the hole!!! if you have any 5/16-3/8 gally brushes, or guide brushes run one through that rod and then wipe it on a paper towel to see how clean your holes are on your new rods. I love breakleen&air pressure&some breakleen the blow out with air pressure.you can clean them with soapy water first with the brush then the breakleen&air...again.then oil/lube

Mon Nov 07, 2016 5:51 pm

mark tucker wrote: you need to make sure the threads in the rod are perfectly clean then oil or use the lube and they need to be torqued atleast 2 times, I like 3 times, but 2 works. and be sure to have lube on your face of your nuts :shock: the rod serface too as well as in the nuts.(nuts or bolts, they need lube on the face that contacts the rod and in the threads in the rod. like in somebodys sig like....never screw a dry hole....and remember by the time you bottom out there aint much lube on the end..thus add some lube in the hole!!! if you have any 5/16-3/8 gally brushes, or guide brushes run one through that rod and then wipe it on a paper towel to see how clean your holes are on your new rods. I love breakleen&air pressure&some breakleen the blow out with air pressure.you can clean them with soapy water first with the brush then the breakleen&air...again.then oil/lube I go one step further..I run a tap in holes,die over threads..I use Mobil 1 for torque lube,but not so much I get it in the engine..Don't like running synthetic for break in..Used to be a VW/Porsche mechanic,been building Harley engines for 30 years..

Mon Nov 07, 2016 6:17 pm

I dont do the tap&ties as they can remachine the threads, gauld the threads or just make the fit loose. usualy just a real good cleaning will do.

Mon Nov 07, 2016 7:32 pm

I've been pretty meticulous about cleaning during this assembly. The rods all got a bath in solvent, and scrubbed with tooth brushed, and threads cleaned with bore brushes. The machine shop did some grinding on them, and I wanted to be sure they were spotless. Plenty of lube on the threads too. I did take the two lower stretching bolts out of there locations, and swap them to others, same results. The threads are clean with no rough or tight spots.
I got some info from ARP, and CB.
CB says to torque them to what they use when they are honed, 29 ft/lbs (thanks modok :wink: )
ARP says the preferred method is to torque to equal stretch, the spec given is the max stretch.
I chose to torque the two lower stretching bolts more, so the stretch was .0035 to match the others. I put them in the same rod, torqued them, and checked to see off it was still round with my bore gauge. Torque was 34 ft/lbs, and the bore stayed round.
For a high rpm or power motor, where the limits of an H beam rod might be needed I guess you might torque them to the max stretch spec. For the bus engine this is surely overkill..
thanks, SD

Tue Nov 08, 2016 5:38 pm

mark tucker wrote: I dont do the tap&ties as they can remachine the threads, gauld the threads or just make the fit loose. usualy just a real good cleaning will do.

I'm with Mark on this one, I've seen many cases where the tap or die actually removes material. However, this may also be partially due to the quality of the set. I'm sure that the older American made set you may have gotten from dad or grandpa is far more accurate then the harbor freight variety.

Wed Nov 09, 2016 9:17 am

I love the harberenger of fright tap&dies!!!!! they cut eazer!!! there cheep!! and I go back over with a known good quality tap if needed.( i have 5 china sets & 4 usa good quality sets)(mostly for taping gallys,Ive got the reamers&bought diferent good taps and the china ones always cut cleaner and eazer(on the mag cases).
aoso, most good threads are rolled not cut.cutting is weeker and isant smooth witch creates more friction .i have snappon thread chasers that I occasionaly use on a slightly efed up thread.but not usualy for cleaning unless there is some sealer that I cant get off.the chasers dont cut, I suppose you could dull some taps leading edges on pourpose and use them, but....gally brushes are eazy.old funkey stuff.....I reckon a dead tap would be ok as long as it does not cut at all.

Wed Nov 09, 2016 11:22 am

Here's another vote for thread chasers for cleaning threads

Wed Nov 09, 2016 5:34 pm

Bolt stretch is the way to go if you have the tools.

If not, then the good ole fashion torque wrench is the tool.

Wed Nov 09, 2016 6:05 pm

Dr OnHolliday wrote: Here's another vote for thread chasers for cleaning threads

See....thats a different answer. A thread chaser is the correct tool....and a thread chaser is NOT a tap.

Thread chasers should not have cutting edges. Their only purpose is to remove debris and in a limited fashion, straighten slightly bent threads in soft metals like brass, copper and aluminum. Taps should not be used for "chasing" threads in critical parts.

Yes.....you may get away with it.....but it only takes once that you dont get away with it to destroy an engine. Ray

Wed Nov 09, 2016 8:18 pm

even new rods need real good cleaning of the threads.I see no reason to chase those, but they realy do need to be throughy cleaned.

Wed Nov 09, 2016 10:20 pm

mark tucker wrote: you need to make sure the threads in the rod are perfectly clean then oil or use the lube and they need to be torqued atleast 2 times, I like 3 times, but 2 works. and be sure to have lube on your face of your nuts :shock: the rod serface too as well as in the nuts.(nuts or bolts, they need lube on the face that contacts the rod and in the threads in the rod. like in somebodys sig like....never screw a dry hole....and remember by the time you bottom out there aint much lube on the end..thus add some lube in the hole!!! if you have any 5/16-3/8 gally brushes, or guide brushes run one through that rod and then wipe it on a paper towel to see how clean your holes are on your new rods. I love breakleen&air pressure&some breakleen the blow out with air pressure.you can clean them with soapy water first with the brush then the breakleen&air...again.then oil/lube

One of your more entertaining posts. Informative, humorously crude (appropriately) and, my goodness, I only had to read it once! :wink:

Thu Nov 10, 2016 6:23 am

Mark is talking about 'tapping holes'...and lube? :lol: