Hey you guys, I have a question about "old faithful" -- my '87 daily driver with 135K miles and no smoke, low emission readings, low oil consumption, high oil pressure, etc.

It's time for a valve adjustment.

I have never used synthetic, have changed the oil every 5K miles (myself) and have the valves adjusted every three oil changes (done by others). This schedule has been kept since the car was almost new.

Over the years, I suspect some of the adjusts were done by amateurs and some were done by real pros. Within those 15K mile intervals, sometimes the valves slowly start to rattle and sometimes they remain quiet -- like this time. (I know the 3.2's valves increase in tolerance with heat, as opposed to most engines.)

The Porsche dealer I have been taking it to for the last few years has an older wrench in there that really knows his (old air cooled) stuff. He did the adjustment the last time and after 15K miles, as I stated above, the engine still sounds great.

Here's my question: is it absolutely imperative to have the valves adjusted every 15K or should I just do it if I start hearing clatter?

Thanks

 

the valves do not always need to be adjusted...but they do need to be checked. Not a difficult task to do yourself once you get all the stuff out of your way. You even get to buy yourself a NEW TOOL! Albeit not a very fancy one, the valve adj. tool is a big help. Good luck

 

True. In addition, a valve that is too tight will be quiet also. These can be worse than loose valves.

 

Bob,

It IS imperitive that you check valve clearances at the prescribed intervals. When valves wear, more often than not, they get tighter since it is the valve seats/faces that "burn down" (so to speak) and this results in the valve clearances getting smaller. Moreover, too much clearance creates more noise than damage (within reason), but too little clearance can really do damage.

Edward

 

Of course you guys are right.

I've adjusted lots of valves in my day, but I know this one takes some time and patience to do right. It'd also be nice to have it up on a lift. I know how it'd be the fist time I tried it too: after it's all back together, I'd worry, with every little click, pop and rattle that I hear, that I must have gotten something wrong and the engine's gonna grenade.

Oh well, better check to see if that old guru is still at the Porsche dealer.

Thanks.

 

Hi. Here's a follow-up that you may find interesting. I just got my car back from the Porsche dealer here in San Diego -- the same one I have used for years and years for valve adjusts (cost $270 plus a free rental car -- I think it's a good deal). The old "guru" P-wrench in there -- the guy who did the valve adjust last time -- said many of the valves were a bit too tight. Hmmm. Seems that they were usually a bit too loose. Tight explains the quiet engine. He said worn valve guides or pitted/worn cam lobes may be the reason why they tightened up (FYI, the engine has 135K on it, with fastidious maintenance, no abuse, and has never been apart, except for a new clutch).

Thing is, the service manager said in reply: "If it is worn valve guides, why does the engine sound so good, use oil the same as it always has ~800/1200 miles per quart, never smokes, passes emissions with exceptional numbers, and has dry and tan plugs?" Good question. He said "Just drive it and enjoy it!" and figured the service bay may be hungry for work right now (tax time and all).

Anyway, the BEST news is that I immediately noticed a significant increase in midrange power! First time I have felt such a difference after a valve adjust. It seems to idle smoother as well. It could be the new summer-season fuel, but I doubt it. Those valves must have really been tight.

Any thoughts?

 

If there was worn guides or worn cam the clearence would have looser not tighter. They are giving you a bunch of it. Most 911 will have worn guides when they have this many miles. If the car dose not use much oil, and does not smoke too much at start up, don't worry its OK.

 

First, I do not profess to be a guru, so do your own research. It is my understanding that valve guides and adjusting the valves are apples and oranges. Think of valve guides as surrounding the long shaft of the valve
as a seal and lateral wall guide. It wears out over time and cannot be adjusted, only replaced. When one has the "it smokes when I first start it in the morning, then goes away after a few minutes" story....it is often the valve guides. The valve adjustment is on the tappet between the cam and valve. The adjustment clearance is the space between the tappet and valve tip. Too close and the valve dosesn't close all the way, too far and it doesn't open all the way. Someone please correct me if I'm wrong.
I bought the tools, but just replaced my flywheel, clutch, front seal, etc so I had the valves adjusted "professionallY while the were there.

regards,
Steve

 

Yes your correct on everything RBC. If you adjust the valves too tight where you put pressure on the valve and tappet you can get partital opening, and too loose will not realize the full potential opening on the top of the cam. The statement I made is that if a cam is worn down then the tappet will won't ride as high on the cam and then be loose on the valve.
As far as valve guide worn will make the valve loose then can have the then offset on the tappet and cause more looseness. Yes guide ware cause smoking, but extreme ware will cause smoking all the time.

 

and keeping a proper adjustment (neither sloppy or tight) will help negate or reduce valve guide wear. I think it's prudent to follow the factory specifications for this in everything from the 3.2's on up. If you are inbetween the 15K interval and you start hearing them - get em checked.

 

How do u hear them? I am a novice in these things... and the 911 engine is certainly not a "quiet" engine with the fan spinning all the time. What type of noise should I be "looking for"? I adjusted the valves and I fear I left them a bit loose...