Cunningham rods

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xxdabroxx
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Cunningham rods

Post by xxdabroxx »

I’m working on a 13.5:1 SBC 383 and picked up my parts from the machine shop today. A while back he showed me a set of rods that he had on his shelf for a while that I had though were CP rods but it turns out they’re Cunningham rods. Small journal 6” A-Beam style rods with 7/16 bolts. The bolts are only stamped with Cunningham rods and don’t look like they are set up for being stretched. The bottom of the bolt is flat, no divot.

Couple questions, did I buy good rods, they look great. They have nice shot peened finish and are brand new in the box. I only paid $300 plus traded a used 350 rotating assembly with stock crank, rods and hyper pistons.

Any ideas if they are still in business or what to torque these bolts to? I called earlier but there was no answer, it was after 5pm but no voicemail. I’ll try calling again in the morning.
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In-Tech
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Re: Cunningham rods

Post by In-Tech »

In general, if using the torque method, a 3/8 aftermarket rod bolt is 50lbs and a 7/16 is 75. I usually use the red bearing lube(I think it's Torco although I started buying it from Childs/Albert years ago, try to wash that off your fingers and it tells a story) on the face and threads, I generally don't like that arp moly crap.
Heat is energy, energy is horsepower...but you gotta control the heat.
-Carl
xxdabroxx
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Re: Cunningham rods

Post by xxdabroxx »

As far as I can tell Cunningham used 296,000 PSI H11 rod bolts made by A1 technologies. Best I can tell is both of these companies are out of business. That seems like a crazy high tensile strength and I'd hate to either over or under torque them.
xxdabroxx
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Re: Cunningham rods

Post by xxdabroxx »

Does anyone have a copy of A1 Technologies "how high can I torque this" http://www.a1technologies.com/images/te ... e_this.pdf ? I've been digging through way back machines and found this link but I can't find the associated PDF.

Found it, but it wasn't much help.
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xxdabroxx
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Re: Cunningham rods

Post by xxdabroxx »

Talked to a guy from the Yellow site that said Cunningham was very adamant about using 90w gear oil and torque to 90 ft. lbs.. Doesn't sound very far off to me based on what ARP wants on their higher tensile strength rod bolts.
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wallbrett
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Re: Cunningham rods

Post by wallbrett »

I have used quite a few sets of custom Cunningham rods in tractor pulling engines. They are excellent rods. I wish they were still in business. I can't find anything close to their quality for the price. Concerning the bolt torque, all the 7/16 bolts are recommended to be stretched to .005 -.006 with torque not to exceed 80 ft lbs using multi-purpose 80w90 gear lube. 3/8 bolts are .005 -.007 stretch not to exceed 55 ft lbs torque. I have a spec card but I'm not sure how to post a pic.
xxdabroxx
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Re: Cunningham rods

Post by xxdabroxx »

wallbrett wrote: Tue Dec 07, 2021 7:25 pm I have used quite a few sets of custom Cunningham rods in tractor pulling engines. They are excellent rods. I wish they were still in business. I can't find anything close to their quality for the price. Concerning the bolt torque, all the 7/16 bolts are recommended to be stretched to .005 -.006 with torque not to exceed 80 ft lbs using multi-purpose 80w90 gear lube. 3/8 bolts are .005 -.007 stretch not to exceed 55 ft lbs torque. I have a spec card but I'm not sure how to post a pic.
That's interesting. My rod bolts don't have a divot in the thread end for a stretch gauge and have a tiny bit of a nub left over from machining right in the center that I think would make it really tough to get a good stretch reading.

I found someone on another site that suggested 90 ft/lbs with the same gear oil lube. He said he'd used a lot of their rods over the years and even noted they suggested the same torque on their top fuel rods.

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