Nuts N Bolts , Nuts N Bolts - We're Screwed



Well after I've read all the Threads & Posts on HB installs and Looking at my own experiences. It is fairly obvious the larger drive pulleys that are currently popular , Have exceeded the design & intended application. The belt speed , Feet per Minute , The larger lever action of a much bigger Drive pulley. Then the very Harness engagement of the Blower Clutch. That clutch engagement is set by the ECU and looks at RPM of the engine, Throttle position , Engine load , Trans gear position & So Forth. NOT the increase belt speed.

The Clamping effect ? load of the bolt head underside and the pressure against the oil pump Sprocket is well exceeded. The Key that is used to engage the Oil pump sprocket sole purpose is to drive the oil pump assy. , but is used in conjunction to help index the HB. , Not drive the HB. It is only engages .310th ! Indexing purpose ONLY, PERIOD. And that has been show through pictures posted by others. So thinking it handles 10% driving load is not the design intent.. Pictures attached will show the load bearing surface's

Now adding a key will certainly Help. But is not the true fix. If you ever noticed after you have removed a HB , there is a oil film on the bore & snout. The oil wicks by the Key , down the key-way . This is a sign of a loose fitting HB. which is normal OEM fit of a .0015, snout to bore finish. And you know this because you can remove & install the HB with your hand and some light pry-bar action. Locktite Red Or Green ( Stud & Bearing Mount) will not help. The slightest Rocking Radial motion between the Crank & HB will loosen the Crank bolt immediately. This is not the fault of the installer , He installs it with the Mercedes Service spec . The true fix is a interference fit & Press on HB along with a new crank Bolt from ARP , to handle the much increased loads and add to a higher clamp pressure needed minimize the unwinding of the thread. What would be really KOOL , how about a Left hand Thread. LOL
Cheers _PTEngineering

 

Oh I saw a post some where on some Crank bolts have Blue Locktite on the Threads . This is True for N/A Motors , but they are a 10.9 Hardness , and silver in color. The M-113 K motor has no Locktie , Has AMG on the top of the Hex and 12.9 Harness
Cheers _PTEngineering

 

Thanks for posting this here to Pat, where it actually counts. Your opinion and expertise far exceeds most on this board, and I really appreciate your feedback.

What would it take to design the interference fit/press on design for our HB and crank? Once it is fitted, is that all she wrote, you would not be able to change out crank pulley again?

As I have already stated, if anyone has contacts at ARP that could propose a test run of the new and improved crank bolt Pat is talking about without having to prouduce thousands, let us know.

 

I'm on the crank bolt. Should have a low volume quote next week.

 

You day mang

Talk to PTE so you know the exact specs he is suggesting.

 

ATI is supposed to get info on a crank bolt also for me that would be just a torque bolt and not torque to yield. Looks like good things are coming for the bigger pulley crowd now.

 

ARP has been pretty clear about what they can do. Already sent them a new factory bolt and all the dimensions they needed. Once I get a firm commitment from them I will send the proposed dimensions out to Pat if ARP lets me.

Btw - if anyone wants head studs I can get them but they are a whopping $20 each! I'm sticking to factory bolts at that price.

 

Or perhaps using one of the "diamond" encrusted washers like GM began using on their Gen4 engines in 2009 to help with harmonic balancer grip.

 

Pat, one other thing I was thinking about was a stepped bore with a press fit only at the last 1/4" of the snout. This is so that you could still have .100" to align the key way and at least something on the snout tip where I would expect the most loading and movement to be centered properly. The other answer is dry film lube to get the fit.

 

This thread could also be titled “mind your nuts and screw to win.”

Solid intel from PTE once again. Thank you!

 

+100000000000000

 

Looking forward to seeing an ARP part number for a crank bolt...the question would then be how much torque would you use on it?

An ARP crank bolt may have saved those members who installed the Red Spoof Racing pulley.

 

I saw a post some where on some Crank bolts have Blue Locktite on the Threads

 

The E55 section is where I need to be on this forum. I've been posting stuff in the CL section and get right next to zero help on technical information. This stuff is great.

 

Pat...always cool to read your shop talk! Hope all is well!

 

That is for the M113K non-supercharged motors, they use that crank bolt for the HB.

 

Thanks for your efforts brotha, this will be major if we can get a bolt that can be tq down even harder for us big pulley guys. I like where this is going

 

Isn't that simply said as M113? Not M113K Non-supercharged...

 

 

geez, you guys are like scientists.......(no sarcasm, honestly)

 

Didn't want any onlookers to be confused

 

bump for update on the bolt being made by ARP.

any more word?

 

They are almost done. As soon as I have them I'll post up. Literally supposed to ship any day now.

 

something to consider. your going to a bolt that can be torqued more than oem. this is a press to fit application. so the bolt is pressing against the h/b and in essence squeezing it against the crank. with the larger pulleys not having a way to secure them from being turned with the bolt this will add stress to the keyway, and possibly damaging it. theres a reason the oem pulley has a special tool to ensure the h/b doesnt move when the massive torque is applied.
i have used patricks products and belive me when he speaks listen! .001 is were he starts and refines from there!

 

Ok, had to read the thread. You guys are correct. Slip fits, keys and long bolts won't hold heavy loads and can be a problem The best solution is a shrink fit where the hub is heated to about 250/300 degrees put on and allowed to cool. The hoop stresses are intense and give the power to hold. However I am sure you see the problem heating. Seals. Of course the front seal won't take the heat unless it is a mechanical/carbon ceramic type seal. All of this runs the cost up. I just worked on an Aircraft engine that has a flywheel opposite the prop. While starting the enginer the 4 bolts that hold the flywheel on sheared off flush. The solution was to (no said this would be easy) drill out the hardend bolts, Replace with higher grade steel AND drill to accept 3 additional 6 MM hardened steel pins. This required flywheel replacement and precision jig drilling. Ganted the Aircraft engine is VERY expensive and the results of inflight failure is a bit more of a problem than calling a tow truck.

This problem of crank pulley staying on can be solved but probably the best solution is the hardened bolt, key and locktite.

This means if you want to pull it this will be a major problem as you must heat the pulley and it will destroy the rubber dampers.

So short of these measures the hardened new bolt and key is probably the best metnod for a car engine. The Corvette LS engine had this same problem until the bolt was added. My LS1 does not have the bolt and I suppose one day the pully will give me the same issue you have on the MB. My E500 doesn't have enough HP to have this be an issue.