8mm 1.25 pitch lock nut

[john schlemmer]

hi everyone, any body know if these are ok to use for fasting cam tower to cylinder heads on a 3.0 911 engine? thanks john

[KTL]

Sure you can. The original installation calls for regular hex nuts (and six barrel nuts) with spring/wave washers under the nuts. So you can do away with the spring washers and use the lock nuts instead if you like.

[Flat6pac]

If you're talking about "prevailing torque" they are not user friendly as they lock on the threads distorting the threads.
I put a bottom end together, broke a stud with them and had to open again to remove the stud and replace. Got most of the hundred on the shelf.
Useful on the worn exhaust studs.
Waves washers and regular nuts is the way to go.
Bruce

[KTL]

Use nyloc flange nuts. Under $10 for a box of 100.

McMaster-Carr

[Flat6pac]

Putting nylon inside the motor?
Nothing that I build....
Bruce

[theiceman]

Just as a point of interest I wanted to replace the regular nuts and washers inside the case where the timing chain housing fastens on ( two each side ) I went with the deformed thread style locknut, as I too was uncomfortable with nylon inside the motor. As pointed out you do have to keep in mind that you lose some of your torque to the thread fastener itself but for a chain housing I figured I was okay.
Not sure about a cam housing, I might stick with the plan on that one.

[boosted79]

Use the original nuts and wave washers with Loctite blue, good for 300F. If you have 300 F there you have much bigger problems.

[theiceman]

Originally Posted by boosted79

Use the original nuts and wave washers with Loctite blue, good for 300F. If you have 300 F there you have much bigger problems.

which post are you referring too ?

[KTL]

Well I stand corrected. Forgot the "wet" areas inside the cam housing (three per cylinder) would do better w/out nylocs. That said, the prevailing torque nuts in oiled enviros are not a bad way to go. The oil penetrates the threads and less likely to break a stud taking off the nuts.

On the exhaust studs in the heads, screw that I won't use the prevailing torque lock nuts. That's just asking to break a stud or at minimum back out a stud (not the end of the world, I know). The weight of the exhaust hanging on the studs keeps the regular nuts from coming loose. And the other fastenings not vertically loaded by the weight of the exhaust (crossover pipe, cat & muffler joints) rust quickly enough that the lock nuts are pointless.

[chris_seven]

Doesn't it depend on the type of Locking Nut?

A Typical Kaynar in an M8 x 1.25 has a prevailing torque of around 4 lbsft and shouldn't cause too much damage to threads.

Philidas nuts are de-pitched and shouldn't damage threads slightly more than a K nut but again have a prevailing torque that can be quite high.

Binx Nuts are also de-pitched and seem to cause more damage than a Philidas nut depending on the strength of the stud.

Stover nuts have deformed threads and tend to be more aggressive than Kaynars.

All locking nuts will cause some damage and using a washer with a locking feature may be a consideration if this is critical.

Schnorr or Belville Washers may be an idea.

[boosted79]

"which post are you referring too ?"

chain boxes, I would not hesitate to use Loctite 290 (green med. strength) for the cam towers, they are flooded with 200f oil. If you can't remove the nut with hand tools then heat it with a heat gun. you have to heat to 250C (480F) to break it loose, if the cam towers get that hot then you also have other problems.

[theiceman]

okay fair enough , I think the cam towers would get well above 300F as they are bolted right to the head but who knows . Point is they did a pretty good designing this so it all should work. I did read somewhere that the chain box nuts were converted to the deformed thread type lock nuts in the later years, I just cant remember where.

[Flat6pac]

The prevailing torque nuts came into factory vogue around 86 or 7. They were used on the perimeter of the case as the only place I have seen them. That's why I ordered some to use on the perimeter, tried and didn't like them.
Bruce

[boosted79]

I'd be surprised if they operate that hot, maybe on a very hot shutdown due to heat soak from heads into the towers. Otherwise I'd think there would be evidence of oil coking inside the towers which doesn't seem to be evident, the oil flow is enough to keep them relatively cool. On diesel's you always let the EGT get down to 300F before shutting down to prevent oil coking on the turbo bearings. Another reason why I won't use the cam oil line restrictors, IMO.

[KTL]

The Stover or "top lock" nuts seem to me to be fairly tame in grabbing threads. Sure they require some considerable torque to thread onward, but they don't seem to harm the threads too much. I've used the Kaynar/jet nuts on similar sized brake rotor bolts (actually 5/16-24 fine thread) and they bite into the threads pretty hard, stripping off the thread plating. I chose to use lubricant to protect the threads during assembly.

I don't think these nuts really have a problem with coming loose. They certainly don't need threadlocking compound. That said, i've often found that the wave washers lose their effectiveness over time. Obviously the washers should be replaced if old. But my point is that over time their spring effect relaxes and that's my justification for using a lock nut vs. the washers since the locking nut retains most of it's locking effect. Nylocs are probably the exception here as the nylon degrades over time. I simply figured that a flanged lock nut takes care of both the locking and avoidance of a separate washer. Though i'm pretty sure the need for a washer here is minimal.

I think the studs that the towers bolt to are under a good bit of stress, most likely from heat cycling? I've found quite a few of them over the years that won't take the required 18 lb-ft of torque, which is not a lot of torque. I was surprised to find them wanting to pull out of the head. Not sure how often people check these studs, because i've not heard much mention of them over the years. Maybe i've just run into some towers that have been over-torqued and pulled the threads in the heads.

As an aside here, to me the cam towers are the most finicky part of the engine. They have so much going on in them that they really should be treated with care more than they typically are. Its one of the most abused parts of the engine in terms of poor cleaning and preparation, along with heat affect.

Put a tower on a flat plate some time and surface it. It's twisted in all directions, which indicates to me that it is dimensionally unstable. All three large sealing surfaces (heads + two valve covers) are often very uneven. So too is the cam bore end surface for the camshaft thrust plate, and that's why that gasket can easily leak. Not to mention some of the damage that occurs from people driving out the rocker shafts. Then there's the cam bores and the spray bars........ Like I said, this part of the engine has a LOT going on with it and should be carefully inspected & cleaned.

[john schlemmer]

the cam towers on the engine in the car leak so bad , the car caught fire. that's why I/m asking about lock nuts. one would think here would be a thin aftermarket gasket avaliable for this stage of assembly. thanks all for the in put john

[john schlemmer]

forgot to mention, the car didn't get hurt . I put it out fast. john

[SCadaddle]

When we built my SC engine 4 years ago, I paid a visit to a friend that owns a fastener supply company. Showed him the usual nuts that hold the cam towers to the heads and he handed me a bag of about 100 of them, gratis.

We start assembling things and before we can get some of the nuts to the proper torque they start stripping out, verified by removing them and examining under a jewelers loop. Start looking at the rest of them in the bag. Appears the manufacturer drilled the holes too large before threading the nuts and there is very little consistency in the lot. Call my friend and ask him where he sourced the nuts in question----"China, they ALL come from China nowadays."

Needless to say we sourced new nuts from a reputable known source that supplies such to be used in this application.

[KTL]

Well keep in mind that the gasket affects the height of the cam tower relative to the chain housings. So that can affect how the cam bore aligns with the bore in the chain housing. That said, there are spacers or shims that engine builders have made to compensate for machining of other parts like the heads or the cylinders. Because if you cut the heads or the cyl tops too much, the cam housing doesn't sit far enough outward to align with the chain box. Hence the use of the shims, which also act like gaskets because I think they're typically made of copper.

If your housings are in OK condition but just a bit "twisted" i'd have them machined. It's not a lot of $ to have someone put them on a surfacing table and get them flatted out. cgarr here on the forums can do them for you. Here's a video of how they're generally done. https://www.youtube.com/watch?v=aWLsKUJCy0A

[theiceman]

john check out the ultimate sealing thread , its actually quite good and discusses sealing products and gaskets.

Kevin If you fly cut the heads you will shift everything closer to the case , but then if you put your base gaskets and shims in the bottom of the cylinders you sould be back where you started. Either way I found enough room in the chain housings regardless around the cam . its not really a "bore" but just more of just a hole with a big gasket and oring . But you are correct , you can add a thicker gasket or shim from the chain housing to the case or remove it all and just use sealer depending what you need.

I would suggest leaking of the cam towers in general is a failure of the sealant bond and has virtually nothing to do with the fastners used.