What to know/hear valves need adjusting on a 3.0L

[liberty43]

Bought an 81' 911 SC this winter and never noticed the 'tick-tick-tick' chatter until this summer when I started driving with the windows down. No documentation on when the valves were last adjusted. So my questions are: What is normal valve chatter? What might tell me they need to be adjusted other than "every 2 years or 10K miles?" Lastly, if they haven't been done in a long time is it imperative to get them done asap? Thanks

[E Sully]

The valve chatter is always noticeable. It is important that the gap is set correctly. Too small a gap could burn a valve. I would suggest getting the gaskets and feeler gage and spend a couple hours getting to know your engine. Maybe there is a Pelican near by so you can listen to another engine to become familiar with the normal sounds the flat 6 makes. They are not quiet like a water jacketed, hydraulic lifter engine.

[liberty43]

Thank you Ed,

I had a 87' 911 prior to this and cut my teeth on a Bug, so I'm cozy with the chatter. But it seems a bit loud and was wondering if this meant time to adjust. No loss of power and idles fine though. But I'll take your advice. Thanks again!

[Flieger]

Valves get tighter and therefore quieter with miles.

[liberty43]

T.O!

Thanks for the reply... and wow, you've got my favorite 911 right down to the color (color?).

[Flieger]

Thanks. Our Porsche engines make a lot of noises- like a symphony. It is hard to tell without experience where the particular sounds are coming from. Even tiny exhaust leaks can make lots of noise. This commonly happens if the heat exchanger flanges are slightly warped.

Usually the driver is just being too worried.

Whereabouts is Magalia?

[liberty43]

I whole heartedly agree. I hear everything. It can be both dreadful and joyful (mostly joyful).

[liberty43]

Oh, in the foothills of the Lassen National Forest east of Chico.

[Flieger]

Nice photos in your garage. Looks like some stunning scenery and good roads. If you are ever in the Malibu area, let met know and we can go for a drive through the canyons.

[liberty43]

No the roads are terrible here, just awful .

Thanks for the compliments, I will let you know the next time I'm down there, me loves the "Canyon!" And same, if you ever want to tour the Sierras, let me know.

[Hodgey]

Originally Posted by Flieger

Valves get tighter and therefore quieter with miles.

Flieger.....how does this happen then?

[dshepp806]

Originally Posted by liberty43

Bought an 81' 911 SC this winter and never noticed the 'tick-tick-tick' chatter until this summer when I started driving with the windows down. No documentation on when the valves were last adjusted. So my questions are: What is normal valve chatter? What might tell me they need to be adjusted other than "every 2 years or 10K miles?" Lastly, if they haven't been done in a long time is it imperative to get them done asap? Thanks

The interval is probably 15K miles. However: nothing wrong with checking them more frequently..or, should something still cause "chatter": investigate rockers, etc.

I'd get them adjusted,..and have them pay special attention to any rocker arm related items (positions,..leaks, etc.), funky lock nuts or foots.....might as well inspect it all when the covers are off....

Adjustment of valves? A given....irregardless of any history.

Best,

Doyle

[Canada Kev]

I sounds like it's time to do them now. Not because they might be making excessive noise, but because you don't know when they were last done or have any idea of their current state. For me, it would just be a simple peace of mind thing.

The car looks pretty good, BTW.

[Flieger]

Originally Posted by Hodgey

Flieger.....how does this happen then?

The valve needs to form a complete seal to its seat in order to transfer heat into the head and prevent valve stem melting (mostly on the exhaust valve). The complete seal also keeps all the combustion pressure in the chamber to do work on the piston.

Because of this seal and high temperatures, the valve head microscopically welds itself to the seat every time it closes (once the engine is not stone cold). When the valve opens again, it rips some metal away from the seat/valve interface. this causes the seat to erode, even though it is very hard. The process is faster with higher valve accelerations and seat pressure.

Due to the erosion of the valve seat/head interface, the valve starts to sit deeper in the head. This means the stem is now closer to the rocker arm and the clearance has decreased. If this is allowed to go on too long, the valve timing will drift enough that the valve will not be closed long enough for heat to transfer properly and the valve cna overheat and drop the head into the engine.

[rusnak]

I agree with those who say you should adjust them.

I just spent half the day adjusting mine, changed the cap and rotor, fuel filter, etc. And it never fails: each time I wonder if it's really worth the trouble and each time I'm amazed at how much more torque and power the engine makes.

[BK911]

Originally Posted by syzygy

I sounds like it's time to do them now. Not because they might be making excessive noise, but because you don't know when they were last done or have any idea of their current state. For me, it would just be a simple peace of mind thing.

The car looks pretty good, BTW.

+1.

What is the worst that could happen if you adjust them? They were already adjusted and you wasted a couple of hours, but now you know.

What is the worst that could happen if you dont adjust them? Boom.

Easy decision.

[Flieger]

I did not mean to not adjust them, I just wanted to say that valves will be noisier when the gap is opened up during adjustment.

[CharlesJones]

Originally Posted by Flieger

Valves get tighter and therefore quieter with miles.

I really don't mean to be argumentative at all, but surely the valves get looser with miles? Everything I have read says they get noisier and looser over time due to rocker and cam lobe wear and the slight backing off of the rocker grub screw. Also, after adjustment an engine yields more power, which presumably is because the valve is open for longer due to the play in the rockers being reduced. If they got tighter with miles I would thought the engine would have reduced power after valve adjustment.

[Flieger]

This is the story I hear from my mechanics and I am sticking to it. There is less wear on the cam area due due to the lubricating oil film (provided you use Brad Penn) . As for the grub screw, well, I gues the locking feature on them is good enough.

Originally Posted by Flieger

The valve needs to form a complete seal to its seat in order to transfer heat into the head and prevent valve stem melting (mostly on the exhaust valve). The complete seal also keeps all the combustion pressure in the chamber to do work on the piston.

Because of this seal and high temperatures, the valve head microscopically welds itself to the seat every time it closes (once the engine is not stone cold). When the valve opens again, it rips some metal away from the seat/valve interface. this causes the seat to erode, even though it is very hard. The process is faster with higher valve accelerations and seat pressure.

Due to the erosion of the valve seat/head interface, the valve starts to sit deeper in the head. This means the stem is now closer to the rocker arm and the clearance has decreased. If this is allowed to go on too long, the valve timing will drift enough that the valve will not be closed long enough for heat to transfer properly and the valve cna overheat and drop the head into the engine.

[rusnak]

You guys have a very interesting debate going on here for sure.

I recently was asked to adjust the valves on a friend's 911SC that had been driven too many miles without a valve adjustment. I found probably two valves way way way too tight, three too loose, and one just a little too tight. The ones that were too tight were like two full turns too tight. I thought the valves would have hit the pistons and blew up the rockers, but who knows why the engine still runs to this day and passes smog now. Chalk it up to flat topped SC pistons maybe, I dunno. I guess the clearance is more than 2 mm?