Valve Cover Bolts

[J. Huber]

Those three on top. How tight should they be?

James
63 230SL

[TheEngineer]

one mkg = 7ftlbs and you better get a torque wrench that has maximum setting of 30ftlbs or so. If you use your big torque wrench, it is most likely inaccurate at low range.

[J. Huber]

Thanks. Unfortunately, the only torque wrench I have is my right arm...loose, sort of loose, tight, and really tight...

I noticed the bolts looked sort of loose -- they were. I started to take a ratchet to them but thought I'd ask... How tight is 7 lbs? -- just to get me to a mechanic...

James
63 230SL

[ja17]

Hello James,
Over tightening these valve cover bolts can damage the valve cover gasket. Severe over tightening may cause the valve cover hold down brackets to squeez inward, touching the camshaft causing a mysterious tapping noise in the engine.
I have a good Snap-on "click style" torque wrench, however I could not resist buying another at Harbour Freight. It was chrome, in a case, 1/2" drive rachet and was the "click style". It came with a lifetime guarantee. It was on sale for $9.95. I have been using it for two years now. I keep checking it with my $300.00 Snap-on torque wrench and the Hrbour Freight one is still accurate! They also had inch pound torque wrenches which would probably work fine on the valve cover bolts.
In any case if you have no tgoque wrench, most experienced mechanics develop a feel from experience. just snug the bolts up using several passes. Do not overtighten. Go back later and look for leaks and tighten a bit move if needed.

Joe Alexander
Blacklick, Ohio

[tuultyme]

Where is a good place to get the copper(?) squash washers that go under these bolts?  Hardware or regular auto parts stores do not carry them.  Or are just any washer OK to use?

Bruce; 268Blaugrun(green) 1970 280SL; IL

[J. Huber]

Well, I decided to just give them a turn until they grabbed. They were maybe a 3/4 turn from snug. What's interesting is the cover has not been off for at least 4 years. So could they have just worked loose or were they that way since then? Hard to say.

I also shot over to the auto parts store to see about torque wrenches. They had the ratchet-type that had a range from 10 ft.lbs and up and another that said 120 inch lbs... Also some banjo-looking thing. If I did the math right, aren't the first two about the same? Since they didn't go as low as 7, I didn't buy one. Do they make one that goes that low? The parts guy, said 7 ain't much -- just a snug turn.

Thanks.

James
63 230SL

[A Dalton]

Small , low torque fasteners use an Inch/Lb. torque wrench, not Ft /Lbs....
 Ft/lb = 12 in/lbs.

[Naj ✝︎]

JH,

 

quote:What's interesting is the cover has not been off for at least 4 years

The bolts are trying to tell you something:
About time you had the cover off and valve clearances checked etc.[:p]

naj

65 230SL
68 280SL

[Benz Dr.]

I've NEVER used a torque wrench for this job. It's a feel thing and the rubber gasket will slowly squeeze down which makes the screws go loose. I tighten the screws until they're fairly snug which I'm sure is a lot more than 7 ft lbs, but failure to tighten it down will cause it to leak particularly around the screws - new seals or not.

The covers are often warped as is the top of the cylinder head so it's pretty important to keep the valve cover with the head if possible. Old gaskets always leak and tightening the screws won't help much.

Only thing I use a torque wrench for is cylinder head screws, brake calipers and wheel screws. I don't use a dial guage to set end play on the front wheel bearings and yet I use all kinds of fine instruments to make very small measurements which can't be done by feel.

Most of the torque specs are not high enough around the engine and so you have to do these things by feel. No doubt an inch pound torque wrench would be usefull in some places. However, you can't go by these things all the time. Manifold nuts have to be more than the book while oil pan screws are often less.
 Any screw going into aluminum should be done with a small 3/8 or 1/4 inch drive ratchet and always by feel. Hold the handle close to the ratchet head and feel for how the screw is turning. If it's binding you have to start over as it may be cross threaded. If it's not feeding in it could be stripping the threads out. If it's turning well and then stops with a bit more of a turn you have to stop too. Any more and you could break it off. Spark plugs should ALWAYS be started by hand and done by feel - unless you want to strip out a spark plug hole. 22 ft lbs is pretty tight and some will pull the threads out if you go that high when they're marginal.

The same goes for removal. I try it with some medium force and if it won't move I use light taps with a hammer. If nothing moves I use a variety of methods from impact gun to a long piece of pipe or heating the screw. This depends entirely on the size of the screw and what material the screw is threaded into. Aluminum will usually give you the most trouble.
 I find stuff like WD40 to be useless as a penatrant but once it starts to move then you can use something like that. A bit of penatrant as it's cooling ( after heating it up ) will soak in and help removal. Some things like king pins are just hacked out without mercy - you're not going to save anything anyway.

Daniel G Caron

[Naj ✝︎]

Thanks Dan,

That is good torque-talk  

naj

65 230SL
68 280SL

[Ben]

When I was an apprentice mechanic I stripped and sheared plenty of bolts until I developed the "feel", even using torque wrenches properly set. As Dan points to, the torque wrenches are good in certain areas and help when you dont have the experience but they are a guide only !

Thankfully I havent stripped a bolt in a while, although when rebuilding my 113 engine I replaced as many as I could and cleaned out all threads. I still managed to shear the little hollow bolt near the water pump housing. It was original and didn't enjoy being moved, it snapped straight away ! I had to carefully drill the guts of it out and re-tap. I am alo living with a broken bolt on my thermostat housing. I decided to check the operation of the 'stat during the summer and soaked the threads for a day or two with WD40. The first bolt snapped instantly so I left the rest alone, it doesn't leak and according to the gauge the 'stat works !

BTW "PlusGas" is the best penetrant I have ever found, they use it alot in the airline industry and it beats WD40 hands down !

"Leave well enough alone "

Regards,
Ben in Ireland.
'64 230SL 4sp.

[Naj ✝︎]

I'm a 'plus gas' user as well.
The WD in WD40 stands for water dispersant and thats the only thing its good for!!

naj

65 230SL
68 280SL

[J. Huber]

Thanks everyone. Now, Naj. I keep staring at your comment about the bolts telling me something... half of me says it was tongue in cheek, the other says you really mean it...

When is it time for someone to take a peak at the valves? I confirmed mine were last adjusted in March of 2000. The engine has run very strong since then. (and to be honest, the lack of mechanical troubles in recent years has allowed me to throw lots of money towards the suspension and other things).

By and large I am fond of Ben's adage to "leave well enough alone..." but just curious what you all think.

James
63 230SL

[Naj ✝︎]

Hello James,
My take is, valve clearance generally decreases with wear and use. If not checked at regular intervals, you could end up with burnt valves.
Recommended interval is 'E' service every 12k miles.
naj

65 230SL
68 280SL

[Benz Dr.]

Valves on gas engines tend to open up over time and to much valve lash will really wear the cam lobes.
Diesels tend to close up over time. Never found this to be anything other than what I've seen.

Daniel G Caron