#%@$*!!! Valve adjustment!!!!!

[gerard vaglio]

Arrrrrrrg!!!!!

I’m in the process of adjusting the valves on my sc... AND LOSING MY MIND!

The first time I did the procedure it took almost all day and I was a little conservative, adjusting everything a little on the loose side. When I was done the car ran fine but the engine didn’t have as much power.

So like a crazy person I decided to do it again. This time I adjusted everything tighter against the feeler gauge. Now that everything is snug the engine does have more power. Amazing how that works???

The problem is that I’m still getting a loud tapping from one valve. I’m fairly sure its coming from the drivers side on the top which is good because I don’t have to drain the oil to remove the valve cover and fiddle with it.

But I’m confused about how to proceed though.

If the valve is very snug against the gauge already why is it tapping so loudly? Is it safe to adjust a valve a little tighter to quiet it down?

Some details:
The engine has 140,000 miles on it, has never had any work done to it and generally runs very well. Before I adjusted the valves there was a slight tapping but not as loud as the tapping I’m getting now. It sounds like only one valve is making the noise. The last time it had an adjustment a Porsche mechanic did it and told me there was one valve that he had a little trouble with but didn’t want to over tighten so he said I might hear a little tapping which I did but it wasn’t bad enough to be annoying.

So, can I tighten further then snug against the feeler gauge?

[Zeke]

That would not be the best idea. You have to have sufficient valve clearance to prevent burning the valve. Something else is wrong and I'd look into it further or get it over to a shop fairly soon for analyisis of the problem.

[Eagledriver]

I believe the spec is 004 plus or minus 001. So I set mine to 003. Less noise and more power. Obviously you have to be careful to not go under the 003. This is done cold. The clearance gets bigger when the engine is warm or hot.

[john walker's workshop]

the trick is to be able to get the feeler gauge to go in and out right between the point where it slips in and out fairly easily and where it traps the gauge enough to kink it. use a twisting motion to work it in and out. any time it slips in or out without the twisting effort, it's probably too loose. two or three twists in or out without kinking the gauge is good. you could also have a broken outer valve spring, common on SCs. if you can push in on the rocker fimly and make it move, the spring is broken.

[markwemple]

Correct me if I am wrong, but isn't the clearance .004 only. No plus or minus. And, that as the engine heats up, things become tighter. That's why the engine is noisier at startup. (not the pro here but do believe I am correct on these)

[gerard vaglio]

Thanks for the suggestions. I'll look at the springs as well and see if that is part of the problem.

Since the engine has been running so well for so long (before my adjustment that is) I tend to think I'm doing or not doing something thats contributing to the problem.

While I'm figuring this out does it hurt the engine to drive it with a loud tapping?

[markwemple]

I wouldn't. If you don't know the cause, assume the worst! (then have a beer once you find out it was no biggie)

[island911]

Originally posted by markwemple
Correct me if I am wrong, but isn't the clearance .004 only. No plus or minus. . . .

± .002 . . .on my 81 SC, anyway.

[RazorRacer]

I've noticed my valves tapping more since I tried to adjust the valves. I had it redone at the Swiss Garage. It may be that you notice the valves more because you are now listening for it.

[aigel]

+/- .002, it's printed right there on the sticker on the inside of the enigne lid. I think it is the same for all these engines, at least up to 89.

Don't attempt to go tighter. If it makes a noise, it is more than 4 thousands. You may have just plain messed up.

George

[350HP930]

I'm suprised no one has mentioned yet that your valve guides could be shot.

At 140K miles I would bet that is the case. If you have a properly adjusted valve that still makes noise that is usually always the cause. Also take a careful look to make sure the cam lobes and followers look OK since they are usually about the only other thing that creates valvetrain noise on a properly adjusted system.

At 130K miles on my turbo the exhaust guides were so shot that the valve heads could move back and forth almost a millimeter when open.

[ubiquity0]

Originally posted by markwemple
Correct me if I am wrong, but isn't the clearance .004 only. No plus or minus. And, that as the engine heats up, things become tighter. That's why the engine is noisier at startup. (not the pro here but do believe I am correct on these)

Doesn't the clearance increase when hot??? My engine is 'tappier' warm than cold.

[markwemple]

My understanding is that metals expand therefore the whole system should tighten up. The .004 is to allow for the expansion rate. The no plus or minus must be through all the non-factory books I have read like BA's, as I do remember it being stated that you want it dead on at .004. Atleast that is my goal. Heck, when doing a bug engine I go for exact, why not on a porsche too!

[island911]

Consider that the .004 is to allow for the differences in expansion rates PLUS wear (valves slowly seating further in, between servicings. )

[markwemple]

Forgot about the wear factor. So I guess that .004 is optimum when new. (like when I adjust my valves for the first time on my rebuilt heads!!)

[Wil Ferch]

911 Engine usually opens up valve clearances as it gets hot....not tighter...

Valve clearances should be done when at "ambient" conditions. Say 68 degF ( 20 degC). Hmmm....that means if I do my valve adjustment in my very cold garage in winter....maybe "spec" would be "0" clearance at 20 degF ????

the .004 is on the engine label of my 85 too..but no +/-

--Wil Ferch

[island911]

Originally posted by Wil Ferch
. . ..
the .004 is on the engine label of my 85 too..but no +/-

--Wil Ferch

"no +/-" . . what the. . .?

Ah, it's a Carrera.
. .. everybody knows regular Carreras are less tolerant that the World Dominating SuperCarreras.¹ MUHAHAhahahaha. . ..

1) AKA- 911SC, SC. Offer may expire without notice. Not intended for export to Cuba. This has extreme fun factor, but is not a toy. Choking hazard avoided when used properly. Not labeled for individule resale. Limit one to customer. See your Doctor before use.

[avi8torny]

Originally posted by Wil Ferch
911 Engine usually opens up valve clearances as it gets hot....not tighter...

--Wil Ferch

I thought the clearance gets TIGHTER when the engine is hot.

Did I miss a meeting or did thermal engineering change since my days at Notre Dame

[island911]

I think both happen.

Thermal expansion: Aluminum(head) out-paces steel(valves) . .. but the exaust valves see more heat.

[Wil Ferch]

All of us look up to certain "guru's" on this list and others. On the Rennlist pages, "the man" is usually Walt Fricke. Here is *one* response from him that supports my own contention that valve clearances open up as you get warm
-- Wil Ferch
-------------------------------------------------------
List: 911




Date Posted
7/18/2001

Posted By: "Walter Fricke"
Message:
Scott's memory of the factory procedure is spot on - we are told by the =
factory and other manuals to adjust the valves on a cold engine, and =
accordingly that is the practice I have always followed (other than in =
exigent circumstances). VWs were the same.

Someone else verified my memory of the one time I checked what happened =
when the engine heats up - that the clearances actually open, at least in =
our 911s, as they heat up. Scott got me thinking, though, about why there =
isn't a "hot clearance" spec which would yield .004 when it cooled down, =
so you could do it either way.=20

One likely reason would be that a cold engine is probably in a pretty =
consistent range, say 50 to 90 degrees F. A hot engine might vary a lot =
more in the temperature of whatever metal parts count, so there might be =
more variation in what the clearances when it cooled down were. There is =
hot and there is really hot, and just warm, and so on. You certainly =
wouldn't want a negative clearance at any time, so unless you had a chart =
and measured how hot something was, it would get complicated, and what =
about the last valve you did as things cooled, etc.

But this raises a different question: why do you need 0.004 (or the =
decimal equivalent) of cold clearance? Is this because if the engine gets =
really really cold (say minus 40 degrees F), the clearances will close =
more and you might end up with valves which wouldn't close?

If that is all there is, a gambling man might think he could gain some =
power by setting his cold clearance at say 0.001 for the summer racing =
season. Or even set them (for racing engines) at some small positive =
value, so as the engine was carefully warmed up you would get a really =
minimum clearance at operating temperatures. Though that sounds like =
you'd be better off getting a cam with a few thousandths more lift and a =
touch more duration, assuming your class rules allowed changing cams.=20

The only other thing I know about clearances is that my cam grinder =
(Elgin) specified the standard 0.004 clearance for their 310 grind I used =
in my 2.3, but 0.008 for their next larger 315 grind I have in the 2.7, so =
that is what I set my race engine at. It isn't even obnoxiously noisy =
(considering its use, of course) while idling. So Elgin sees valve =
clearance as having some relationship to cam profile, though why there is =
a relationship again eludes my understanding - if it is to compensate for =
too steep a cam ramp why not change the grind? =20

Maybe with overhead cams with rocker arms there is some kind of rocker arm =
bounce which occurs as the cam enters the base circle and keeps the valve =
a touch open, which can't happen if there is more room for it to bounce? =
Is it possible that while the valve to rocker clearance opens with heat, =
the valve to piston clearance decreases with heat?

However, these are academic questions, as I continue to follow the factory =
(or cam grinder's) recommendations and set cold and at the specified =
value.

Walt Fricke

>>> "Scott Booth" 07/17/01 02:50PM >>>
Walt suggests that valve clearances increase as the engine heats up, and
recommends the obvious experiment for verifying this...

For some reason (meaning I read it and forgot where, or was told it and
forgot whom) I think that this is the reason that we're supposed to set =
the
valve clearances on a completely cold engine (as in, let the car sit
overnight and adjust the valves without starting it in between). If we
adjusted the valves while the engine was warm, they'd be too tight =
relative
to the spec (since it's talking about a cold engine) at all engine
temperatures, and they'd be *way* too tight when the engine is cold. =
Since
tight valves can burn up (while loose ones are just annoying and
inefficient), it would make sense that it's important to follow the
recommended procedure.