[1965tripleblack]

Should I use LocTite on flywheel bolts?
Pressure plate bolts?

 

[72sbc427]

I do. I use red. It was recommended to me by the Centerforce tech I purchased my stuff from. But to be safe, it doesn't hurt to ask the manufacturer of your parts.

 

[TCSS1970]

Factory used lock washers. ARP said to install with oil to there torq setting with no lock washer. I did what ARP said since I used there bolts. And by the way the factory ones looked like they were the originals from 1973 and were still tight as the day they were installed.

 

[Tom Mobley]

usually don't use loctite on a bolt that tightened with a torque wrench.

 

[1965tripleblack]

I used red for both. Reason I asked the question was that the ARP flywheel bolts' instructions recommended moly grease or assembly lube (their own brand, of course!), or motor oil. The PRW flywheel instructions stated that LocTite should be used for the fasteners. Pressure plate from RAM had no recommendations, and neither did the ARP clutch bolt kit.

I assembled the whole thing last Thursday, and have engine/trans back in the engine bay.

Obviously, I see that there is no "right" way to do this.

I used the lower torque values, as if the LocTite has the same lubricity as motor oil.

Joe

 

[79943]

I personally think that in an application where a fastener is going to see the type of thermal cycling, vibration and shear stress that it will see in a flex plate or flywheel bolts that it is a good idea to very carefully set the torque AND use Loctite. What the proper torque will do in addition to holding the fastener in place is to transfer some of the stress into tensile on the bolt rather than all shear. The loctite can add a 25% increase in what is needed to detorque that bolt. At least Loctite 272 does when it is cured because I just had the opportunity to have some testing done at work last week that demonstrated that.

 

[1965tripleblack]

Permatex ThreadLocker Red 27100.
States that it "may require heat" to remove.
Been using it for years and never once needed heat to remove.

 

[JJ'65]

I personally think...

What the proper torque will do in addition to holding the fastener in place is to transfer some of the stress into tensile on the bolt rather than all shear...

Interesting observation. Is it the case that the stresses are by design transmitted in shear in the applications referred to? I would suppose that the fasteners would be tapered or interference fit if that was the case; but I don't know. Who knows?

My $0.02

 

[Tom Mobley]

pressure plate bolts are shouldered, the flywheel is countersunk to accept that type bolt. The bolts sort of act as dowel pins, all the load is in shear. The threads sort of act to keep the pins from falling out. flywheel/flexplate bolts aren't that nice, they're real short, not any length to get a stretch going. Those are about the only bolts I'd be tempted to use loctite on. Neither of these bolts are a source of problems on Chevys.

 

[79943]

The thing with using the proper torque on a bolt is that the intent is to create a clamping force such that it is holding the two parts together thru the tensile strength (linear) of the bolt rather than just the cross section (shear) of the bolt. This can be the case regardless of the geometry of the bolt, i.e. tapered or shouldered or whatever. As long as there is a head there to create the clamp. That is the true stength of the bolt, its cross section, which increases both tensile and shear stength as the diameter increases, however, the tensile strength is always much greater than the shear.

 

[charbilly2001]

Factory used lock washers.

Actually the factory used "Star" washers that dug into the flywheel and held the bolt in tension but it's a small point. I guess you could call them lock washers.

 

[oldtimr]

Actually the factory used "Star" washers that dug into the flywheel and held the bolt in tension but it's a small point. I guess you could call them lock washers.

Seeing as how they are available in 3 flavors
internal lock
external lock
and combination internal/external lock

and they are available for left hand engagement as well

yep, you could call them a lock washer. But they ain't a spring style lock like a regular one, they are multispringededed. Like you said they gouge the pee outta stuff.

I put antisieze on flywheel bolts, tighten them to about 80 to 90% US(Ultimate Strength, which is just shy of yield strength). Bastards ain't coming out, nor stripping.

Loctite has ruined lots of threads, on removal. At least on cast it does. Good steel it usually is ok just a pita to clean.

edit: I may be FOS on the left handed star washers but man I sure seem to remember something about em from way back in the cobwebs. Seems like you could just flop it over for left handed but there's some little technicality with doing that?