Valve adjustment nut torque... What torque do you use?

[HFR_Racer]

Hello everyone..

I'm adjusting my valves and am highly interested on what torque should be used for the adjustment nut. I used 20 ft-lb as suggested in another thread on this site and I stripped threads off of one of my adjustment screws.

Honestly, 240 (in-lb) 20 ft-lb seems like alot of torque here since the jamb nut is only 1/2 thickness. I was thinking that 120 in-lb (10 ft-lb) is pretty tight. I don't feel that I can get much more without stripping threads from the adjustment screws..

I am highly interested in your opinions as well as the factory torque spec.

I've seen another thread on Pelican that mentions 12-13 ft-lb.

[Walt Fricke]

Well, I use tight plus a hair. Works for me. The box end wrench handle is short enough that I doubt I could get 20 lbs/ft if I tried that hard.

[HFR_Racer]

Thanks Walt..

I should have asked in the engine forum first. That would've saved me a damaged adjustment screw. I guess it's time to remove a rocker shaft. I hope that I can remove only the center rocker shaft and that I don't have to remove an adjacent one as well.



I checked the service manual and found no torque spec. I'm sure I've got the other adjustment nuts too tight now. I'm going to go back through and re-adjust / re-check / re-tighten to ensure that I didn't strip anymore.

[Walt Fricke]

Wayne's book on 911 engine rebuilding does not give a torque spec, at least not that I could find. I think he covers valve adjustment in 101 Projects, but I can't find where my copy of that went. Anderson doesn't mention torque for these. My Bentley for the 3.2s is silent on these.

The normal method of tightening these nuts is to hold the shaft in position with a big screw driver, and to tighten the nut with a box end wrench. Short of using a crow's foot, you won't be able to use a torque wrench for this anyway. And you'd need something a bit offset, as the valve cover studs get in the way.

This is an M8/1.00 bolt. Per a chart Maryland Metric has on their website/catalog, if these are 8.8 grqade, they can be torqued to 38 N/M, which is 28 lbs/ft. If 12.9, 52/38. This is higher than one sees in specs for these parts, though. If one were to go by that alone, you wouldn't expect that 20 lbs/ft would distort threads on the nut or screw or the rocker. I've accumulated maybe 50 spare rockers in various conditions and stages of being reconditioned, and for sure sometimes it is very hard to get the screw part out of the rocker. I take that to mean it is the rocker threads which distort. Perhaps that cast metal, in a place where it can't conveniently be hardened, is the weak link and the source of distortion? However, you striped the adjuster threads.

[HFR_Racer]

Yes.. That is one strong M8 jamb nut.. I would've figured that the jamb nut threads would've pulled out versus the adjustment bolt. I would say that the torque figure would be ok if you use a full nut, but since it's a half nut I would imagine that the torque value should be reduced. I'm highly confident that if I put 20 ft-lb on the jamb nut for all of my rockers then 90% + will fail the threads. Therefore, 20 ft-lb is no good for me..

Also, you can easily torque these using a torque wrench. I simply used a 3/8" drive in-lb torque wrench with a 6" extension. I probably could've used a 3" extension but my knuckles would be pretty close to the valve cover studs.

I'm not at all sure why your thinking that a torque wrench can't be used on the jamb nut for the valve adjuster bolt??

[Ronnie's.930]

Originally Posted by HFR_Racer

Yes.. That is one strong M8 jamb nut.. I would've figured that the jamb nut threads would've pulled out versus the adjustment bolt. I would say that the torque figure would be ok if you use a full nut, but since it's a half nut I would imagine that the torque value should be reduced. I'm highly confident that if I put 20 ft-lb on the jamb nut for all of my rockers then 90% + will fail the threads. Therefore, 20 ft-lb is no good for me..

Also, you can easily torque these using a torque wrench. I simply used a 3/8" drive in-lb torque wrench with a 6" extension. I probably could've used a 3" extension but my knuckles would be pretty close to the valve cover studs.

I'm not at all sure why your thinking that a torque wrench can't be used on the jamb nut for the valve adjuster bolt??

How do you hold the shaft/screw steady with a screwdriver if you have a socket over the jam nut?

[Walt Fricke]

Ronnie - my point exactly. Thank you.

All the books show a picture (some of these pictures I am sure are simply copied from some other book) of a box end wrench on the nut, and a screw driver in the slot on the screw.

To be sure, after one had gotten the nut "tight enough," I suppose you could put a torque wrench with a socket over everything, and give it the final twist to some set value. Then check the clearance one final time, and cross fingers it hadn't tightened up.

Nuts sold as jam nuts are typically reduced height. This suggests to me that the engineers who can figure such things out have determined that for jam nut purposes (keeping another fastener from loosening) a full depth nut is not needed. This does support the point that less torque would be appropriate. The Maryland Metric table did not include jam nuts, and I should have noticed that.

Otherwise you are reduced to using a crowsfoot, with an extension for clearance.

Tain't worth it, Macgee.

[lindy 911]

A torque wrench with an extension is no longer accurate. The extension becomes part of the torqued connection and will flex and absorb part of the applied torque. I have a very accurate technique; it's called "third knuckle white". Pull on your boxed end 13 mm Snap-on wrench until your third knuckle turns white, then stop. If your forth knuckle turns white it's too tight. Other wrench brands will have differing results.

Sorry to be a smart ass but the nut is just a jamb and is not clamping any components that would require an even pressure clamp like a case through bolt or perimeter bolt.

Lindy

[john walker's workshop]

you guys actually use a torque wrench on rocker nuts???

[GrantG]

Originally Posted by Walt Fricke

The normal method of tightening these nuts is to hold the shaft in position with a big screw driver, and to tighten the nut with a box end wrench. Short of using a crow's foot, you won't be able to use a torque wrench for this anyway. And you'd need something a bit offset, as the valve cover studs get in the way. .

Stahwille torque wrenches have box wrench attachments (among many others). They are my favorite torque tools. Not saying this is necessary, but I think this is the best solution for someone who thinks it is...

http://www.stahlwille-online.de/index.php?amac=03030002000e&sid=003ce291c682a316564ea12e3e02f47a&lid=2&mid=2&shid=&scmd=plist&pcid=4893&cid=5022

[Walt Fricke]

John

Not I, said the little red hen.

Don't on valve covers or oil drain covers or chain housing covers or or intake/exhaust manifolds or engine /transmission carrier fastemers (other than the four big bolts) or what holds the engine to the transmission or lots of things. Never had a problem.

Case bolts, through and perimeter, rod bolts, head nuts, cam carrier nuts, flywheel bolts, pully bolt, CV bolts, and most transmission stuff - all that gets torqued. Except for the few where it is inconvenient, like the case bolts in the bell housing. Something like the white knuckle system seems to do fine there.

[HFR_Racer]

Great input everyone.. I replaced the two-(2) valve adjustment screws that I stripped out along with the rocker shaft seals. All is good now.

Yes, I used a 6" extension on a torque wrench. The deviation in torque is not significant. I verified that the adjustment screw didn't move after the final torque was applied. I used 10 ft-lb as a final torque for anyone that is interested. I also removed excess oil from the adjsutment screw and nut prior to torque.

I find it humorous that the original poster of the 20 ft-lb torque value chimed in as well. Save me $40 bucks next time and don't post erroneous information please.

I truly appreciate all of the great information on this forum. Next time I'll await further confirmation of information. I figure that this was easy since many of you have likely performed a valve adjustment in the past.

HFR_Racer

[JJ 911SC]

Just finish my first (ever) valve job.

After reading this thread yesterday, I check 5 different sources (Wayne 101, Wayne Engine Rebuild, Bentley SC, Bentley Carrera & Haynes.

None give a torque value so I went with Walt advise; tight + hair using using the 13mm Jam Nut Valve Adjustment Tool. Work like a charm.

[HFR_Racer]

Very nice tool.... $45 bucks seems a bit steep though.

[JJ 911SC]

Originally Posted by HFR_Racer

Very nice tool.... $45 bucks seems a bit steep though.

Afer reading a few horror stories and local shop charging $500 + for the job, $45 is peanuts...

This was my first adjustment (never seen a "live" valve before), went around in less than hour.

Half that time was to find where and how to get the blade in oand out on Intake # 1

Since I had 5 spare blades, I did not brake the original one (reverse Murphy Law)

[KTL]

I had an adjusting screw on one of my rockers in the '87 that went funky. You could only turn it in so many turns before it would bind. That's an example of what happens when you over-jam the jam nut.

Plus, as mentioned by Walt, when you overtighten them you can't get them out of the rocker arm when the rocker is removed from the engine. It's either the threads got booged by the jam nut or the slot in the adjuster stud has expanded the width of the stud. So you end up popping the adjuster foot off of the stud to remove it from the rocker.

Snug/mild resistance is plenty good enough for these jams. Gorilla tightening not required!

[redstack]

reviving an old thread.
I just spent half a day doing three valves. the whole lock nut thing was kicking my asp. I had a great Porsche dial indicator from the fellow who rents out his lift for those who ask nicely. But it took me over an hour on the first exhaust valve. The lock nut wouldn't move easily so I would fight it the whole time.

But I am so glad that I did the job as one valve was very tight. So I was getting better and hope for improved time as I go. Then there's the whole check them again thing.

[chris_seven]

Originally Posted by lindy 911

A torque wrench with an extension is no longer accurate. The extension becomes part of the torqued connection and will flex and absorb part of the applied torque
Lindy

Lindy, I don't agree as you can't really destroy a force at the level we are discussing and the elastic deformation in the extension will have no real influence.

I would agree that the twist will make angle measurement impossible but the applied force will be unaffected.

If the extension is too long and affects alignment then measurements may also become inaccurate.

Thin Lock Nuts are interesting products.

In general there is no formal specification for this type nut although they are commonly manufactured from a Grade 4 material, in general the softer the nut the better it works but within sensible limits.

It isn't common practice to specify a torque for this type of nut as they are only used to prevent loosening due to vibration and if preload was an issue they would be used in conjunction with a full strength nut which would be used to apply the correct force.

For this application preloading of the adjuster isn't required.

In general these nuts only need to be tightened to a 'snug' fit which I realise isn't entirely helpful but there isn't really a good answer.

I would tighten them by around half a turn from their 'closed' position which should be good enough and much easier to see.

It may also be more consistent in terms of the effect on the tappet clearance due to movement whist tightening the lock nut.

[mreid]

Originally Posted by lindy 911

A torque wrench with an extension is no longer accurate. The extension becomes part of the torqued connection and will flex and absorb part of the applied torque.

Sorry to be a smart ass but the nut is just a jamb and is not clamping any components that would require an even pressure clamp like a case through bolt or perimeter bolt.

Lindy

Your first paragraph is not true. The second is completely true.