ARP connecting rod bolts machining help

[optmaxx]

So I got a call from the shop that's working on my block for my stroker build, and they told me that a small part of the ARP bolts need to be machined so that they can slide all the way in? I bought 112-6001 rod bolt kit, and I can't picture just what he's talking about, so have you guys heard of machining the bolts so that they can fit into the 4.0 connection rods for the stroker? I plan to see him before he closes, and I'm hoping I can give him a clear answer.

[SilverXJ]

I have never heard of this. Which part is it and what casting number rods do you have?

[nicpaige]

Did he say if he was talking about the head of the bolt interfering or the shank not fitting in the rod? If it means just a VERY slight flat to one side of the head to clear then no big deal but if its the shank not fitting I would be concerned.

[optmaxx]

I went to see what he was talking about, and it's the step just below the head of the bolt. It looks like there are three steps before the threads, so it's the one right below the head and he's tried hammering and an air gun but it seems to bottom out. He measured the old one and then the ARP bolt in front of me and there seems to be a 0.004 difference in that area.

I'm not sure of the casting number of the rods, but I'm using the rods from the 1996 4.0 block they came with. I gave him the ok to try and press them in cause he was worried about breaking the rods, so I said to try one and see what happens because I don't think I can return the bolts anyways; unless I'm told here not to get them pressed, then I'll call him in the morning to tell him not to try. My last resort would be to use new OEM rod bolts I guess.

[SilverXJ]

He measured the old one and then the ARP bolt in front of me and there seems to be a 0.004 difference in that area.

That doesn't say anything. The bolts are a press fit. But the bore and new bolt needs to be measured to determine the press fit. Measuring the old one does no good. I do not know the press fit measurement. Might want to give ARP a call about that.

I'm using the rods from the 1996 4.0 block they came with.

They shouldn't be a problem then. I was concerned that they may the later casting numbers which I don't think people use much.

I gave him the ok to try and press them in cause he was worried about breaking the rods, so I said to try one and see what happens because I don't think I can return the bolts anyways; unless I'm told here not to get them pressed,

That is typically how rod bolts are installed. He should determine the press fit measurement first though. But, he should know this already. Also, putting the bolts in the freezer or dry ice and then heating up the rod can help.

And no, machining the bolt isn't a great option.

[Russ Pottenger]

Those bolts will be fine.
They will have more interference fit than the stock bolts, but they go in with no problems.
Just make sure he coats the bolts with a liberal amount of the moly lube supplied with the bolt kit before
pressing them in.

My preference is to use engine oil on the threads and tq to 40lbs

[optmaxx]

Yeah, I didn't like the idea about machining the bolts either. Thanks, at least now I can tell him that for sure the bolts need to be pressed, it surprised me that he didn't try, but I guess he was just covering his butt. I definitely got to make sure that he's using the grease though because I didn't check, that will probably make it a lot easier for him. So the grease goes all over the bolt and except the threads?

[SilverXJ]

My preference is to use engine oil on the threads and tq to 40lbs

Why do you prefer engine oil over the ARP lube?

it surprised me that he didn't try, but I guess he was just covering his butt.

I hope that is the case.

So the grease goes all over the bolt and except the threads?

According to ARP use the grease on the threads as well when torquing the nut to 40 ft lbs. Different lubes will change the torque value and I can't recall which is more slippery, atm. Is he resizing the rods after he installs the bolts?

[optmaxx]

Yeah, he'll be resizing the rods after he installs the bolts.

[Russ Pottenger]

I have found that not all moly lubes are the same.

10 to 15 years back a customer gave me a set of Crower rods to resize.
I called Crower for torque/stretch numbers. He said to use Moly. I told him I had
the ARP stuff. He went on to tell me to use the Felpro Moly, and said there was a difference.

Its of my opinion that its important to replicate the same lubes and fastening specifications as the manufacture
or machinist as closely as possible. Any auto parts store will have a can of 30wt dinosaur oil, but they may not have
the correct Moly.

[Russ Pottenger]

.... And it's a absolute must, If you press a bolt out you will need to resize the rod.

[optmaxx]

He still had trouble pressing them and recommended machining them, so I called ARP to ask them if it was ok. The guys at ARP tell me machining them shouldn't hurt them, but said that I have the wrong bolts for the 4.0 rods, and that I should have gotten the 146 kit because the two kits are different.

I went ahead and let my machinist machine the bolts since it doesn't seem to hurt them, and I don't think there's much more difference between the two bolts since they've been used before in stroker builds. I was tempted to order the 146, but it doesn't seem like there will be an issue using the machined 112s. My rods have the 691 casting.

So, he should use the lube on the bolts when he's going to resize the rods? I think that's what I told him.

[optmaxx]

All the while I kept wondering if it would have been easier for him to machine the rod bolt holes, but it kept slipping my mind. My rods must be weird haha.

[SilverXJ]

I used the bolts spec'd for the 258 with out issue on my 4.0L rods. I wonder if there is actually a difference besides the part number.

I personally would use the ARP lube. Just remember to use it if you ever need to remove the nuts and re torque them. As Russ said different lubes create different bolt stretch/ torque load. ARP specifies 40 ft lbs with their lube.

Just took a look at the Instructions for the 4.0L bolts and teh 258 rod bolts. Their stretch figure/ torque figure is different for the two kits.

4.0l: http://arpinstructions.com/instructions/146-6001.pdf
258: http://arpinstructions.com/instructions/112-6001.pdf

That leaves me thinking what exactly is the difference between the bolts... or just a different stretch number. Use the 40 ft lbs though as you have the 258 kit.

[optmaxx]

It would make me happy to know if the 112s were once used in stroker kits. The ARP guy didn't make it sound like I shouldn't use the 112s, he just said "If it were me, I would use the 146s...", but he didn't make it sound urgent enough. If he would have said no don't use them, then I would have ordered the 146s.