KPrecision Rod Bolts

[Kurt Bogerman]

Guys,

Call me crazy, but I feel really bad that my isolated modification of these bolts has become the focal point of public opinion regarding the product. I'd still love to know more about how they perform in the WB820s in which they were intended to be used. As they say, "No News is Good News". Except when 'No News' goes unreported.

I started this conversation in order to point out that I used the bolts in a manner that was inconsistent with KPrecision's intentions. I would never have started this conversation if my situation hadn't been made public elsewhere on the forum. My methods have been questioned, and I am completely open to the possibility that I may have compromised the structural integrity of the bolts by "quenching" them in water. I was aware of that risk, and made an effort to keep the temperature under control, but maybe the temperature spiked in a moment and the bolt crystalized. I am inclined to think that the real issue was the fit of the bolt in the McCulloch rod. I initially thought that it was too tight, and I wonder, had I a better feel for what's acceptable in such a close tolerance fit, if I would have continued to proceed. Jeff has not had the time to work with my rod, as he is moving his shop right now, so the jury is still out on the matter.

To be clear, I am not at all affiliated with KPrecision, but I have kept in touch with Jeff, and he is aware that his product is under close scrutiny. He has had the following things to say:

"From our standpoint we have done a lot of research on the material we chose to use. We have had testing done by a 3rd party. Every run of bolts has 4 that are randomly picked to be tested. They must be 275-285 ksi and 50-53 RC if they do not pass they get scrapped. Every batch will always get tested... We do everything on our end to ensure quality (testing and inspections). All of the materials we use all have certifications to ensure quality of material."

With regard to comparisons to Dave Bonbright's screws: "The material I use is a material that is used in the aerospace industry. It is not the same material that was used in the original screws. The alloy that I use is much more cost effective and is actually a little stronger in important areas. My supplier can get me the material that was originally used for the screws but at the cost for it the market would not support it. The material that I do use is also used in building formula 1 engines that rev 19.5k along with parts that would go on jet plane's landing gear, etc."

"I will be, in a few weeks, sending another batch of bolts with a 3/16 hex head to heat treatment. They will be for the 820 engine. After I get everything moved to our new shop I will be running a short run of 150-200 bolts for the MC engine."

"I do hope that everyone truly understands that this issue will be fixed but it will have to be a separate bolt just for the MAC rods."


With fingers and toes crossed for a break in the weather at Avon this weekend,

Kurt

[steve welte]

Kurt don't feel badly about it. Feedback is needed but often misunderstood. Everything takes a process. I remember when i sat down for the first month at S&S Cycle with the dealer/customer base fielding the tech line and warranty problems. I told my wife "I'll soon be fired" as I did about $200,000 of warranty the first month. Instead I got praise for taking care of the customer and doing what I was supposed to do. If everything was simple everyone would be doing it.

[ted johnson]

Kurt, I do not personally believe that the mod you did to shorten the screws had anything to do with the bolt head popping off. I have shortened screws to use in my Mac engines before. The thread class on W.B. rods is something I do not know. Both Mac and W.B. rod were originally meant to accommodate the standard GR8 socket head screws, which are ordinarily class 3A threads. If the GR8 socket heads work in Mac rods, a W.B. screw should also work fine. You were careful not to overheat the screw when you shortened it, and, indeed, you did not even get to torque the screw. The only issues I see with K Precision screws in Mac rods are: 1. Was the hole in the Mac cap chamfered to clear the underhead fillet on the screw? 2. Is the counterbore in the Mac cap large enough to accommodate the washer face on the new screw? 3. Is the new screw's unthreaded shank longer than the distance from the counterbore in the Mac cap to the broken face of the cap so that it bottoms in the thread in the Mac rod itself? If the answers are YES, YES and NO, then the shortened screw should tighten down. Of course, lubing the threads is important. TJ

[Kurt Bogerman]

Guys, I appreciate your comments. I don't feel sorry for myself. I kind of have a personal code of ethics that requires me to own my own experiments. Maybe I'm trying to get everyone to see things that way. I think this comes from having owned several 1980s AMCs. Oh, the parts interchange stories I could tell! I've never, ever had to wonder, "Will this void my warranty?".

Ted, your three answers:
(1) Yes. I chamfered the cap with a conical Dremel tool in my drill press. Not elegant, I admit.
(2) Yes. The flange of the bolt head fit in the counterbore of the cap.
(3) No. The shoulder of the bolt was not too long.

So, theoretically, it should have worked. However, it broke well before the head was seated, and it broke in the threaded area of the bolt, so none of those factors came into play. I'll attach my only photo of the crime scene for reference. I apologise for the imperfect focus. The burnished spot on the broken stud is where I decided to polish smooth the tip of a drill bit.

[ted johnson]

I still say it ain't YOUR doing! TJ

[Kurt Bogerman]

For what it's worth...

I ran my 91B, which I had assembled using Jeff's KPrecision rod bolts, in Sportsman Rear class at Cuddebackville this weekend. Despite having to work through some carburetor and intake issues early on, I wrung it out hard and there was no kaboom.

While testing the engine at home last weekend, burning methanol fuel, I experienced an issue with a cracked carb body. Not having a suitable replacement on hand, I cobbled together a replacement carburetor using the double pump stack on a gas carb body. While running 50/50 gas/methanol through the ersatz carburetor, my Digatron tachometer recorded a 14270 RPM free rev. I don't recall seeing that reading in real time, though I had seen it momentarily tick past 13K. I wouldn't have pushed it to do 14+ intentionally, but the Max Recall function says that I did just that. I was not able to run a CHT sensor at that time, hence the implausible 874° reading in the attached photo.

I ordered a replacement alky carb on Monday, which was delivered Thursday afternoon, right before my departure for Cuddebackville. I installed the new carb at the track and proceeded to have a host of issues. A who's who of talent stepped in to rescue me. Once we had the induction system sealed up and the carb dialed in, I observed sustained 11K-plus RPM intervals and a max RPM of 12600 while coming down the long Cuddebackville straight. Max temp was approximately 385°

I didn't set any track records with my best 52.295 second lap time and 48.88 mph, and I didn't get on the podium at the end of the day. I did give my 91B a solid thrashing, and it just ran better and better with each session, once we'd worked through the hiccups associated with the trackside carb swap. I expect to be able to continue to operate this mill without incident.

Thanks, Jeff Kniseley, for your gracious customer service this past summer.

Thanks, too, to everyone who offered their advice and feedback regarding my workmanship.

Best Regards,

Kurt

[ted johnson]

Encouraging words, Kurt! Glad you have had success. Ted

[David Luciani]

[Richard Stamile]

My suggestion for what it's worth is DO NOT attempt to cool the bolt when shortening . Let it air cool only. Water is the worst thing you can do. If you were to use anything other than just letting it air cool, oil would be the choice. I would prefer to not even use that. I also don't know what was used to shorten them.  Heat is your enemy (and that cooling process kills the metal) . I use a number 36 belt on a 6 x 48 grinder (usually well worn). I don't get them very hot.

i was thinking the same as soon as i heard cooling and water you want to slow the cooling as long as possible
a can of sand and placing the bolt in when hot is even slower and safer then air cooling