I not too long ago installed an O-ringed hot-rod head. I fastened it by way of a stud kit purchased from PDR, who purchased it from Haisley Machine who apparently made the "Kit" using A1 brand studs, nuts and washers.

The studs were installed and re-torqued as per the written instruction provided in the kit by Haisley including liberal application of the ARP assembly lube.

Ran it like that with a single PDR HX35 hybrid @ 38psig boost (max) and a little W/M. Worked just fine for a year (without looking at dates).

Installed a conservative Twin-Turbo deal that with my current fueling produces right at 65psig boost with roughly 1350*F EGTs. Injection timing is perhaps North of 2.25mm lift. 406hp / 840ft/lbs.


A week later my friend in the top/left of the following image introduces himself. Last week his cousin (bottom/right) showed up.






By way of the printed instruction, the first nut popped at 125ft/lbs (hot).

The second popped at 135ft/lbs (cold).

In each case just checking things under the hood presented with evidence of a head-gasket leak. The first with antifreeze/gasses jetting out from around the broken stud assembly. This most recent with bubbles in the radiator reservoir. Replacing the damaged goods and pulling it all back up to 135ft/lbs cold fixes the leak.



Comments?

 

I think they're selling junk hardware, David.

 

I would like to see more "meat" on those nuts; they look awfully thin to me.

 

Actually, the comparable ARP version is slightly smaller in height.

 

Makes you wonder why some drag cummins builders use only stock head bolts................

 

Nuts and bolts are really pretty basic stuff. Sure, some may be very specially designed to do things like hold heads on engines. But if they are properly made with the right materials and correctly installed, all they do is just sit there and hold things together.

Those are junk.

 

ARP is the only way to go, only $400.00!

 

Yeah, that's just lousy hardware. The truck is not a radical application, there is no reason for them to be failing like that other than poor materials/manufacturing error.

The "out" for A1 that I can think of is the possibility that your torque wrench is way out of whack and you are applying a lot more torque than you think you are. But given your thoroughness I'd imagine you've checked that already...

 

Yeah well, with the first nut popping at 125, I figured such could be the case so I purchased a digital torque wrench that sports a % of error at 1%. The range is up to 150ft/lbs in one tenth of a ft/lb resolution. I'll find the brand/specs when I get home. Suffice it to say it's a VERY nice wrench.

Said wrench was used to pull them back up in repairing the 1st mess. Again in pulling them up Saturday.

 

Cross-check the wrench with the old one, just to be sure.

 

Same here BK. As I'm not intimate with how much room there is to work with, not sure why they couldn't bump them out to the next metric size and add some beef?

 

14 mm studs??!!??

 

Evidently A1 is producing their own nuts now. My A1 studs, purchase a couple years ago from Scheid, came with ARP nuts.

 

12mm.

That's how Haisley's 1st edition of the "Kit" came. Now all A1.


Note the failures are occuring well after the installation.

 

Those look like pretty standard nuts- probably made by SPS or the like. Might be an MS / NAS / NASM spec out there. What strength material are they rated at? 180 ski? 220 ksi?
On torquing the bolts. If I have all the information, I can calculate an angle method instead. The problem isn't just in the acuracy of the torque wrench, but other variables. Looking at NSTC-0803 they list the torque wrench scatter as plus or minus 35% !! You can tighten that with angle OR you can use a crow's foot to tighten and do stud elongation.

ARP and Military hardware is lot tested unless it is a major safety issue- say a wing attach bolt or a helo rotor bolt. So, they make a run of 10,000-100,000 nuts and heat treat. Test 6-12 and if they pass, the lot is good.
Only way improving reliability in nuts is to do something like mag particle inspection on each nut and stud.

Michael