old man neri

[QUOTE=911vet;4927587] What's the harm when they are too tight?

/QUOTE]

The theory is that if they don't close fully or don't close for long enough they can't dissipate their heat and burn out. That's what I have heard anyways.

As for the gasket thing, worry not, I have used the cheap ones and never had a problem. They were grey in colour if that helps.

Good luck and I hope all goes well when you turn that faithful key!

Droops83

Well like I said it's not really possible to ADJUST a 911 valve clearance too tight w/ the feeler blade, but if the exhaust valve clearance is too tight in any engine, Porsche 911 or not, you run the risk of burning the exhaust valve up since if the clearance is less, the valve spends more time open, that is, off of its seat. The valve seat is how the valve dissipates its heat, it acts as a heat sink. Plus, the valve is spending a bit more time hanging out into the very hot combustion chamber during the exhaust stroke if it is open longer, and it's getting even hotter than it should.

On pushrod 356/914 and old VWs, the valves tend to get tighter as time goes on, and this is why it is important to adjust them every 3,000 miles, so you don't burn an exhaust valve. Plus, if the intake valve clearance is too tight, it stays open longer, increasing valve overlap (the amount of time that both the intake and exhaust valves are open at the same time) which if bad enough can affect idle quality and low RPM running (though I do hear that back in the day drag racers who raced their solid lifter street cars would tighten down the intake valves before racing to get a little more overlap and high RPM power).

They can get beat up if it's very loose. A tiny bit too loose isn't bad, it'll just be noisy.


You'll probably be fine. Make sure the sealing surfaces are clean and you torque the valve cover nuts evenly, from the center out, not too tight and use aluminum crush washers and nylock nuts and you'll be fine. I just like the Wrightwood ones best, use them next time. They make a cool kit that has all the valve cover gaskets, sump gaskets for if you have a pre-'83 car, and all the nylock nuts and crush washers for the valve covers, and 2 crush washers for the drain plugs too.

911vet

Thanks for all the info. You explained it well.

I knew the torque of the valve cover nuts was to be 6lbs. Trouble is, I didn't have a good "feel" for how tight that was. After putting them back on, a friend told me I put them on too tight (he showed me how tight was right).

So... tell me what harm I might have done. I didn't crank them down as hard as I could by any means, but I definitely put them on tighter than 6lbs. Probably by quite a bit.

Is it serious enough I should remove them, get new gaskets and nuts, and start over? I haven't started the engine, so I can easily drain and reuse the oil.

Droops83

Well if they are all evenly a bit too tight it might be OK. The issue with overtightening the nuts is you could pinch the gasket and cause a leak, but this is more prevalent in cork or rubber gaskets. It is tricky to gauge how tight to make the 911 valve cover bolts since there are crush washers underneath, and they need to be crushed a bit, and that can throw you off. I stopped using a torque wrench on these long ago since I've done so many now I know how tight to make them, but if I were you I'd invest in a good set of torque wrenches if your are gonna be working on your car much (you'd want a 1/4" drive wrench that reads in inch-pounds to accurately gauge 6 ft-lbs, or 72 inchlbs). I probably wouldn't worry about it, start the engine up and let it warm up and make sure there are no leaks. If there are, do it over again, you won't lose too much oil if you have to take the exhaust valve covers off again.

911vet

So, is leaking oil the only real issue here? I don't think I got them "crazy tight" to the point that I could break one getting the nuts back off. And I put never seize compound on them (yeah, I know, they have plastic inserts but I did it anyway).

old man neri

Ya, I have been having a problem locating a torque wrench that can be dialed in to such a small amount. I did it by feel as well. God only knows if I was even in the right ball park.

I think the worse that can happen is you develop an oil leak. An oil leak out of a 911?...Shocking, I know. I certainly wouldn't undo everything and redo it without being sure you had a leak. Of course, that's just me, I'm lazy and rather drive my car. As for draining and reusing the oil...be very very careful of contamination. I think it's possible to jack up one side of the car, change the lower cover, and only loose a slight amount of oil per side. Might be a better way of doing it. Look at it this way, you may find yourself having to readjust your valves anyway. Fire it up, take it for a cruise. Find out if you are leaking and if your valves sound right and then go from there.

If you still have the older, non turbo style, exhaust valve covers I have heard they could warp if torqued down too much. Not sure on that one though.


Fire her up Shannon! (That is my completely uneducated advise)


-matt

911vet

I like your advice! Makes sense. You are right, I may need to readjust valves anyways.

And good idea about jacking up one side. Will do. (I won't reuse the oil that drains out).

My car didn't leak a drop of oil before all this. Seriously... I never saw one drop of oil on the driveway. So it will be very easy to determine if I've created a leak.

I have the upgraded valve covers. So maybe I didn't warp them.

Thanks for the encouragement. I think I can get some sleep now

Peter Zimmermann

I've just read this thread, at least most of it, and I want to offer some information that I hope clears up a few things. First, let's start with rocker cover nut torque. To expand a little on Chris' correct posts, and to correct an obvious error in other posts, the fastener studs/nuts for the covers are 8mm. The rule of thumb for 8mm hardware is 18 lb/ft. The spec "6 lb/ft" has never applied to rocker cover hardware, and stems from a typo in a Porsche spec book from many years ago. How that spec became gospel I don't know, but it is flat wrong. Most factory lit states that "all M8 bolts/studs on the crankcase and cam housings" should be torqued to 18 lb/ft (25 Nm), and that is correct. Now, there is an additional issue with the hardware, and that is the quality of the crush washers. There are two kinds; (1) Very silver-appearing washers made in Taiwan and other unknown places, and (2) high quality washers, sold by Wrightwood Racing and other quality sources, that are a dull gray in appearance and are probably still made in Germany. The #1 washer will collapse into the stud threads as the nylok nuts are tightened - you don't want those. The #2 washers will retain their shape, even to 18 lb/ft, and will be easy to remove the next time that the covers require removal - you do want those. About the gaskets, the intake covers can be done with the thicker gray gaskets, but the lower covers should be sealed with the green, or blue-green (sold by Wrightwood Racing), thinner version gaskets. It is not necessary, or recommended, to use any form of sealer on the gaskets, or anything at all on the fastener studs/nuts.

Now I'll offer an opinion about the alternate adjustment method. My original thought is "Why?" Why re-invent the wheel? If go/no-go is your desire, get some .005" shim stock, and follow up your .004" setting with it. If it goes in, the valve is too loose. If it doesn't go, but the .004" shim does, you're probably good to go. During the time that I ran my shop I trained a number of apprentices. I found that it took an average of about 20 valve adjustments to achieve success on a car. It's a feel thing, there must be drag on the gauge as it's removed, and the gauge must be able to be re-inserted. I was taught by two factory-trained master mechanics who moved to the U.S. in the mid-'60s and opened an independent Porsche-only shop, called G&M Motors, in Culver City, CA shortly after arriving here. From the start of 911 production Porsche decided on the best, most fool-proof, most efficient method of adjustment - there is no alternate method discussed in factory literature. The crucial part of feeler gauge use is the condition of the shim - as soon as it becomes damaged in any way it must be replaced.

As the 911 engine cools, what is called an oil-lock forms between the elephant foot and valve stem. It is standard procedure to "break" that lock, by wiggling the rocker arm, prior to performing an adjustment.

The method that calls for forcefully tightening the jamb nut until the adjustment screw follows it is, quite frankly, sheer idiocy. All that will do is destroy the threads on the hardware (I know, I've had to remove a number of rocker arms no longer serviceable, chase the threads and install a new elephants foot/screw). The jamb nut should be loosened, an adjustment made, the nut snugged down, and gauge removal/install done. Repeat as many times as necessary, when the adjustment is correct final tighten the jamb nut, while holding the adjustment screw, and check the clearance one last time. As Chris stated, "adjusting" a valve too tight is not an issue because gauge removal is impossible, but too loose will cause premature rocker arm and cam lobe damage.

ne ohio 911

Chris, great advice thanks for the insight. I bet I spent 10-12 hours total when I did mine. I plan on going back in again this winter. Now if I am doing the math correctly, you mechanics are getting about $700 an hour to do a valve adjustment.

Amber Gramps

Pete, let's, just for fun, say that after 68,850 miles my valve covers have never been off the car. What would you do to the nuts to get them off if I took it to you for a valve adjustment? Some have oil on them, some have a green looking crust, some have a brown rust. I'm thinking of shooting PB Blaster on them and letting them soak a couple of days then hitting them with a were brush to clean the bit of thread showing. What would you do?

Peter Zimmermann

Douglas: Just unscrew them, the nuts that you will not be re-using will clean the threads on the studs. You will probably have a few lower studs pull from the cam housing; that's OK, just double nut the stud and remove the nylok nut from the other end. Clean the threads, spritz a little aerosol parts/brake cleaner into the threaded holes, change the double nuts to the nylok nut end and re-install the studs. You don't need anything on them, just screw them in until they bottom out. It's OK to use a wire brush on the rusty stud tips, but it won't help much. I'm sure that the covers must have been off, but if they haven't we've got a real scoop!

Droops83

Good to hear from you Pete, happy new year! Glad you could expand on what I said w/ your experience. I remember when I was first learning how to adjust 911 valves, Henry checked my work, but didn't say anything and let me put one all back together and start it, just so I could hear how noisy is is when they're too loose! I of course had to wait till it cooled down and readjust. But, that's the best way to learn something!

2.7RACER

The "backside method" was developed to address the problem of DIY mechanics difficulty with the traditional method of adjusting 911 valves.

As stated by Peter Z,

"During the time that I ran my shop I trained a number of apprentices. I found that it took an average of about 20 valve adjustments to achieve success on a car. It's a feel thing, there must be drag on the gauge as it's removed, and the gauge must be able to be re-inserted."

The "backside method" eliminates the "feel thing". If the valve is set looser than .0042" at the elephant foot/swivel foot, the .003" NO-GO feeler will slip between the rocker and the backside/base circle of the cam.

Simple, no "feel" involved. It goes in or it doesn't go in. No guess work.

Also no need to loosen the set screw to check the setting. The .003" NO-GO feeler slips into the radius of the rocker and cam, rather than the edge of the swivel foot and the valve stem.

A bonus is there is no need for a "special tool" and spare feelers.
A simple feeler gauge set available from any auto parts does the job and is not typically damaged with use.

The .0025" GO feeler protects against setting too tight. If it won't slip in if the gap is tighter than .0035" at the swivel foot/valve.

This method was never intended for the trained experienced shop mechanic, although it is simpler and faster.

If you are happy adjusting valves as you always have, fine, continue to do so.

If you can spend up to 20 times learning the "feel" continue to do so.

If you want to set your valves once and be able to run a simple check before you button it all up, try the "backside method".

dshepp806

By the book for me.......all of the P-wrenches I know use the standard approach of adjustment. Although the alternate approach does make sense,..still: I go with convention,..yeap,..20 times and it's old hat, I guess....that's what I'll continue to do.

Best,