ARP Rod bolts question

[FastGS-T]

Ok I am purchasing the ARP Rod bolts for my 6bolt build, and I have searched about the machining necessary for them. But I still dont know what to tell my machinist. Anyone got a good explanation for me? Does the bolt holes just need boring? or does just one side need to be bigger? thanks

 

[Raynehr]

Where did you read that you needed machining? The rod bolts shouldn't, the advantage of the arp stuff against the stock stuff is the tensle stregenth and heat resistance. I have built several older hotrods fords and chevy alike, and rod bolts are never an issue for machining, the head of the arp rod bolt is slightly different, changing up from a square (stock) to more of an oval tapered (arp) head. I could see if it was headstuds or mabye even maincap studs, But not rodbolts..

 

[FastGS-T]

well when i searched it said that machining was needed.

 

[Boostedexcel]

you shouldnt have to worry about honing out the bolt holes with the ARP hardware. But you will have to hone the rods back to size after torqing down the bolts, because the caps distort.

 

[92awddsm]

The only machining needed is resizing of the big end of the rod after the arp's are installed. It is the same procedure as any other rod whan replacing the bolts. Your machinist should know this without any information from you. If not, find another machinist.

 

[Steve_P]

The only machining needed is resizing of the big end of the rod after the arp's are installed. It is the same procedure as any other rod whan replacing the bolts. Your machinist should know this without any information from you. If not, find another machinist.

That is correct. I have had rods (non DSM) that the bolt holes had to be reamed out for the bolts to press in properly- they were too tight to press in w/o reaming. This is rare but possible.

 

[Big Woo]

Since the rod bolts press into the rod they deform the shape of the big end of the rod. Basically the cap and rod are cut a small amount on the surface where the two come together. This effectivly reduces the diameter of the big end of the rods when the cap is toruqed in place. Then the big end of the rod is enlarged back to its original specified size by a honing process. Well that is the short version.

Depending on the amount of press that the rod bolts have in the rods will determine the amount of distortion that takes place in the connecting rods housing diameter.

 

[99gst_racer]

Machining is definitely required. It's also important to note that for a fastener to function properly, it must be stretched a specific amount. The material's ability to rebound like a spring, is what provides the clamping force. So to obtain the correct amount of clamping force, a fastener should actually be stretched a measured amount.

1. Reinstall the rod cap and bolts, then measure the free standing length using a mic.

2. Lube up the nuts, and torque them to the recommended bolt stretch.

3. With proper preload applied, have the big end of the rods resized (like 92awddsm stated). This is recommended anytime the rod bolts are replaced. (be sure the torque spec used when resizing a rod and final engine assembly are the same.)

4. Install the rod/piston assembly in the engine using the bolt stretch meathod (same bolt stretch as before).