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X25 · 10-23-2015, 04:06 PM

In other news:
From my build thread:

Quote:

Originally Posted by X25

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2. Oil cooler adapter bolts:
I wanted to tighten the oil cooler adapter bolts while the headers were out, and broke one of them! Thankfully, it was easy to remove the rest of the bolt from the block, or else I don't know what I could even do. I had two more bolts that I've used before during my experiments, but realized these bolts were all stretched!

Take a close look at the bolts. The part of the thread that stays in the engine block is wider than the thread that stays by the oil cooler adapter. These bolts are certainly not up to task. I will talk to Michael @ ImprovedRacing and see if he has better bolts for the job, and will also look it up at my local store (Tacoma Screw) for a better alternative.

And the resolution:

Quote:

Originally Posted by X25

As I mentioned before, I told Michael @ ImprovedRacing about my experience with the bolts, and he got back to me with great information. In short, they take this feedback seriously, and will change the bolts that they use in their kits!

Quote:

Thanks for bringing this to our attention. I have actually never heard of this happen before with other customers.

I discussed it with our engineers and the consensus was that unless there was a material defect in the bolt (unlikely since it happened with multiple bolts), then they must have been over-torqued. These are M6 bolts and the recommended torque spec is only 106 in-lb or just under 9 ft-lb.

That said, we tested a few samples to see at what torque they would fail. At 10 ft-lb of torque, there was no stretch at all and the bolts were fine. However, at just 15 ft-lbs, the bolts stretched and eventually sheared in half. This was a much lower torque figure than we had anticipated.

The bolts are stainless steel and have a minimum tensile strength of 70,000 PSI. We chose stainless for longevity and corrosion resistance. Additionally, because you are screwing the bolt into aluminum, a stronger bolt isn't always desirable because when over torqued you will strip the aluminum threads before the bolt breaks. It is generally considered preferable that the bolt break rather than the aluminum threads become stripped, since that would be more difficult to fix than replacing a bolt.

However, we also feel that the torque at which the bolts failed is a bit too low. So after some deliberation we have decided to switch to Grade 12.9 steel bolts, which have a minimum tensile rating of 170,000 PSI. The downside is that when over-torqued, the aluminum threads in the pan might strip before the bolt fails. But we are also going to add a warning and a note to the instruction manuals with the recommended torque rating for these bolts. We do also recommend adding thread locker to the bolts to ensure they don't back out. But be very careful torquing them down because as I mentioned you don't want to over-torque them.

Do you want us to send you some of the new steel bolts when we get them in?

Thanks,

Michael Ihns

I already sourced the new bolts from my local store: Grade 12.9 M6x25mm @1.00mm thread. The O-rings also need to be replaced each time the adapter is removed. They are 16mm, 1.5mm thick, Viton O-rings.

Michael said the torque rating for these bolts (provided by GM) is a ridiculously-low 106 in-lb / 8.8 ft-lb. In GM's case, the oil cooler adapter is supported by 10 more bolts, so these bolts are only supposed to seal the oil ports; no big deal. In our case, though, they need to support the weight/tension of hoses, the adapter itself, the sensors on it, etc. I wonder if I should stop at 10 lb.ft, or if I should try 15 lb.ft. If it strips, I'm in BIG TROUBLE, but would be nice to know if 15 lb.ft is OK, (and I think it will be).

I will update the first post about the bolts. The new ones are black (not stainless steel), and are much stronger. If you have shiny bolts, you should consider replacing them next time you touch the oil cooler adapter for any reason. The replacement bolts were easy to source locally, but I had to order the O-rings (50-pack; O-Ring, Viton, 16mm ID; http://www.amazon.com/gp/product/B00..._detailpages00).