Stretch those rod bolts

zcoker · 09-24-2009, 04:08 PM

I know that this forum is here to help others, so I thought I'd give it a shot and post a topic on rod bolt installation - rod bolt stretch when using ARP or Raceware bolts. Sometimes we have bottom ends that have already been built but without the good rod bolts. Yes, you can measure stretch with the rods in the case on the cheap. Many here have suggested that this is not possible, and rightly so with a regular micrometer or a stretch gauge. What you need is a good "donor" micrometer, one that you can do without. Cut the ends off even and then taper the flat faces to a cone, leaving just a small point of hardened surface area on the original tips for the rod bolt centers. Then weld the ends to a long bolt. You need to jig the cut ends of the decapitated micrometer as strait as possible on the long bolt before welding. I used a large bench vice. Take the tiny set screws out of the vertical shaft of the micrometer so that you can "zero" in each bolt by turning the shaft. Tighten the rod bolt to torque and then measure again. Easily fits inside the spigots onto the bolt center holes. You have to zero the base of the micrometer to a horizontal range point for each bolt before any torque is applied because each bolt is of a different size. Works great, very precise. I tested this home-made-in-twenty-minute contraption on an ARP rod bolt at the machine shop against their expensive stretch gauge and got equal readings.

boostfix · 09-25-2009, 06:45 AM

Nice! something to add to the garage engenuity thread!

Tools/Methods Showcase - garage ingenuity

LOWFAT · 09-25-2009, 07:58 AM

I just love home made tools. Thanks for sharing!!!

nocarrier · 09-25-2009, 03:01 PM

pretty fart smeller!

j/k!

Nice idea! I love home made solutions!!

"stick it to da man."

occb2 · 09-25-2009, 08:08 PM

Funny thing. I am in the process of rebuilding my 930. I found that the rod bolts have stretched just by removing them. They did not have the SNAP sound when braking the bolt loose. So we ordered a new set.

Rob

zcoker · 09-26-2009, 02:33 PM

Quote:

Originally Posted by occb2

Funny thing. I am in the process of rebuilding my 930. I found that the rod bolts have stretched just by removing them. They did not have the SNAP sound when braking the bolt loose. So we ordered a new set.

Rob

The rod bolts don't have a "snap" sound when you loosen them, and if they are stock, they are already stretched and cannot be re-used. I suggest that you get ARP or Raceware hardware for the rods while you got it apart. This is a smart move. ARP or Raceware rod bolts require a stretch measurement to the manufacture's recommended range else failure is possible - hence what this thread is all about.