Flywheel bolts – Loctite?

[bumble]

I note also that ARP is marketing a range of flywheel bolts. Does anyone have any experience with these? Do they solve a problem?

[Walt Fricke]

For stock motors, there certainly is no problem to be solved that I can see. Stock flywheel bolts do the trick.

For race motors, I still don't see a problem. ARP advertises their bolts as 200,000 pounds per square inch steel, and suggests a 12mm bolt be torqued to 112 lbs/ft.

I make metric 12.9 bolts to be 186,000 psi steel. Factory torque spec for the 12mm bolts is what - 110 lbs/ft? Same as the ARP.

For the 70.4mm 6 bolt crank I torque the factory bolts to 150 lbs/ft. They don't break, and hold the flywheel in place up to at least 8,500 rpm. So I'm not seeing a problem here either.

I don't see what the bolt head looks like in the ARP catalog. If it is the funny sort of multi-leaf clover head they show for flywheel bolts generally, one would need a special socket, wouldn't one?

Now, if they are less expensive, I could see using them. The factory 12mm flywheel bolts are not cheap (though given what they do, perhaps that is to be expected).

But maybe someone has actually tried these, as they make ones for our 6 and 9 bolt cranks?

[PFM]

Walt,

The ARP part number for the 6 bolt flywheel is 204-2802, the set can be had for $35.00, the install sheet says Loctite 242 on threads and ARP lube under the bolt head NO washers, torque is 100 FT/lbs.

The head of the bolt is as Porsche hardware.

No history yet on these bolts but will be installing them soon.

[Ken911]

I always use red loctite and new bolts. I have never had any problems with any thing coming loose or with removing the bolts. I also use blue loctite and new bolts on the pressure plate.

[Walt Fricke]

Well, I think that is a price break. Odd that they would say "no washers." Porsche didn't use no stinkin' washers in this application. Just a stainless steel? or otherwise hardened one piece, six hole part which acts like an imoveable washer.

Wonder why they specify Loctite? Oh, well. I do it my way and it works. You do it your way, and it works. We are both happy.

[1-ev.com]

interesting thread !!!

Any updates since last post? I see they changed website and bols are here http://arp-bolts.com/kits/ARPkit-detail.php?RecordID=1165

and here they are talking about 95 ft-lb http://arpinstructions.com/instructions/204-2802.pdf

also, why not use Loctite 242 on factory bolts? is this Blue one?

Thank you.

[Walt Fricke]

1-ev: Blue isn't strong enough. The 6 bolt, 70.4 cranks had a bad habit of coming loose in high rpm (~8,000 and above) race useage. Stock torque on these bolts is inadequate. I'm not willing to experiment with stock torque and red Loctite, as I suspect it is inadequate also. Nor with the 150 lbs/ft with no thread locker. I had two flywheels get loose before Bruce Anderson tipped me off as to what would solve the problem. If I built a race motor with ARP's bolts, I'd use 150 lbs/ft for torque on the bolts, and red Loctite. Those guys are engineers, but I rather doubt they have tested their stuff on an 8,500 rpm early 911 race motor over an extended period of time.

[Flojo]

spec is:
the 6-bolt version are M12 and torque at 140 Nm, dry, no washer
the 9-bolt version are M10x1,25 and torque at 90Nm, dry, no washer
allways use new bolts!


for spec-/street-/regular- used cars I never heard of using any kind of "loctite" and believe it's just out of fancy avalability and modern "fear" somehow not to trust spec advised torque (that has worked oh so well all these 30-40 years).

[Walt Fricke]

Flo - I agree that for a stock 6 bolt flywheel engine, the factory specs are perfectly adequate as to torque, and don't need a thread locker. The same is true for the 9 bolt later cars. I race one of those in a stock class, I rebuilt the 3.0 motor to stock specs, and it has had no problems with the flywheel coming loose.

However, the Porsche factory specifications are unquestionably inadequate for a race motor spinning consistently over 7,000 RPM. Porsche had no end of trouble with its 2.8 RSR motors, and never actually solved the problem other than pulling the engines after every race and using new bolts.

I had two flywheels get loose on my 8,000 RPM 6 bolt race motor with the stock torque before I learned how to deal with this. After that I've never had one get loose.

Someone else with experience using a high RPM 9 bolt race motor would have to opine on what more than stock, if anything, is needed for those. The wider hub is going to give a better geometry, I suspect, although the unfortunate coincidence of a 4th order node or whatever it is with the crank right on the flywheel mating surface might still be there causing problems.