pressing in rod studs

[TurboBlue]

Can I just install new arp studs in my rods with an arbor press or should I pay the machine shop to do it. Anything special they do here ? I want the job done right, but if I can do it, I want to save the money for other services.

Any advice ?

[mcsvt]

I think they need to be resized once put in. Unless you can check them once pressed in, you may want a machine shop to do them.

[altered7151]

They need to be resized after being installed. My local machine shop did mine for $40, well worth it.

[turbovanman²]

To press mine in, I just used a vice and a socket. Vice jaw goes on the back side and the socket goes over the threads. Tighten up and voila, done. Definatley have a them check after new bolts installed but sometimes, they are still nice and round.

[TurboBlue]

So how do they resize the hole after the stud is inserted ? Is it welded or crimped ?

[GLHS0658]

The cap is ground to make the big end "oval" Then with the new bolts installed/torqued the hole is machined.

Simon, when you install new rod bolts especially aftermarket (ARP), the clamping force is so much greater that it tends to make the big end oval.

You MUST resize the rod.

Mike

[Clay]

sorry, Im not buying "the clamping force is so much greater".

Clamping force is clamping force. You install ARP rod bolds, but you still torque them to the same spec. Clamping force is the same.

ARP rod bolts are excellent quality bolts, but they dont allow more clamping force than a regular bolt. When you press fit anything into a hole like that, the press fit can cause some distortion of the near by bore. That is probalby why you need to resize the bore of the big end of the rods.

[Pat]

sorry, Im not buying "the clamping force is so much greater".

Clamping force is clamping force. You install ARP rod bolds, but you still torque them to the same spec. Clamping force is the same.

ARP rod bolts are excellent quality bolts, but they dont allow more clamping force than a regular bolt. When you press fit anything into a hole like that, the press fit can cause some distortion of the near by bore. That is probalby why you need to resize the bore of the big end of the rods.

Stock bolts are torque to yield, meaning they stretch. Depending on the bolt, age, condition, the they may stretch more or less than others. ARP bolts are set to a specific torque specification. No stretch means more clamping force.

[Clay]

Clamping force is measured by torque.

Stretching vs. non stretching is just how the torque "gets" to the bolt. Just because the bolts stretch does not make them weak, it just means they are one time use.

All bolts stretch when tightened. The difference is torque to yield bolts stretch to the point they are on the border of the elastic vs. plastic range of deformation. They will never go all the way back to "new" length, but this is how they hold their clamping force.

[86Shelby]

When you press fit anything into a hole like that, the press fit can cause some distortion of the near by bore. That is probalby why you need to resize the bore of the big end of the rods.

I've changed several sets of rod bolts with the machines at a machine shop. When you press out the rod bolts you can easily see the bore change shape and then go back to normal as the pressure is released. This is where the need to resize the bore comes from. The half of the bore in the rod itself is now out of round from the stretching out of shape.

The ARP bolts themselves do not distort the bores. Niether does the stress from thier torque specs as long as the same torque spec is used for final assembly and resizing of the bore.

I sorta screwed this last part up while in school refinishing a set of rods. I was unaware the customer was going to use a stretch spec for the rod nut torque. I used the 50 ft/lbs spec that came with the bolts when I resized them. His bearing clearances were too tight because of this miscommunication.

[Pat]

Clamping force is measured by torque.

Stretching vs. non stretching is just how the torque "gets" to the bolt. Just because the bolts stretch does not make them weak, it just means they are one time use.

All bolts stretch when tightened. The difference is torque to yield bolts stretch to the point they are on the border of the elastic vs. plastic range of deformation. They will never go all the way back to "new" length, but this is how they hold their clamping force.

30 ft lbs on a stock rod bolt does not equal the same clamping force as 30 lbs of torque on an ARP bolt. There are stretch variables, friction variables, thread pitch variables, etc that come into play when determining how much clamping force there is at a given bolt torque.

Regardless, as 86 Shelby said, having the rod resized with the new bolts at the specified torque is essential.

Pat

[GLHSKEN]

Bottom line. Don't be cheap here or you will do it again

[GLHSKEN]

K... thread back from the dead. What is the ARP rod bolt torque spec??

Thanks in advance

[turbovanman²]

50 ft/lbs. If there new, loosen and tighten 3 times using ARP moly lube. Ken, I listed all these specs in the FAQ section, hehehee,

[Tim]

I think this whole "you MUST resize the rods when installing new bolts" thing is BS.

Why? Because I had a 2.2 torn apart last winter. I measured the dimensions of the big end of a rod, then I pounded out the old rod bolts and pressed in another pair of rod bolts. Then I put the cap on and torqued it to the normal specs.

Then I got out the micrometers again. There was NO change in the measurements.

[Directconnection]

I think this whole "you MUST resize the rods when installing new bolts" thing is BS.

Why? Because I had a 2.2 torn apart last winter. I measured the dimensions of the big end of a rod, then I pounded out the old rod bolts and pressed in another pair of rod bolts. Then I put the cap on and torqued it to the normal specs.

Then I got out the micrometers again. There was NO change in the measurements.

Haha...then you did it wrong, my friend.

I work with engines all day and resize rods often. #1) you cannot check the housing bore with a micrometer. You use a sunnen bore gauge or a dial bore gauge. #2) The loads from the exact same style bolt to another are not identical, so the stretch can vary, never mind chaning bolt manufacturers. So, this will distort the housing to a degree, or alot of going from oem to arp. #3) Rod bolts are also used to center the cap. Once you change bolts, or even press out the original, and then press the same one back in, the caps will now shift. Some real lucky circumstances, it may not, but 90% of the time, when re-usung rod bolts after cutting the rod and cap, they do.


If you buy ARPs or any bolt (or for some reason even press out and re-use to same ones) ALWAYS have the rod and caps cut and then resized. NEVER install bolts without resizing. Asking for a spun rod bearing this way. I saw one set of BBC rods come in that someone did this to... they got lucky. But if you're fortunate enough to see how far out they get, you certainly won't ever want to go this route again.


BTW... if you were able to use a dial bore gauge you would notice the the big end didn't change much at all on the dimension. But, you must measure all around the housing bore, not just the 12 and 6 o'clock positions. I can assure you, the housing bore is egg shaped and the cap is offset.