Mechanical Overrev - The Plot Thickens

Alright, a little update...

I went to pick up my car after the shocking $2,500 estimate to repair the bent valve. Turns out the head was already in the machine shop and parts ordered. Ok, I said, well, at least it will be done quickly.

However, when stopping by the shop to see how it was going, I noticed that the engine had not been removed from the car. I didn't really get to see anything, but I could see the left side timing chain dangling in the breeze. Anyway, got the call tonight that everything was back together and running great. Turns out it was a bent exhaust valve on cylinder number 2.

Sure enough, the bill comes in at $2,400 and change. I thought ouch, but it was over and hopefully fixed right...lesson learned. While looking at the bill, I noticed 27 hours in labor! Again, this is with no engine removal! Help me out here guys, but that seems almost impossible. $150 in parts, plus $200 in machine shop, a few gaskets...etc.

My wallet was bleeding profusely, but I got in my car and started to leave. Upon starting, I thought I noticed the same vibration that had developed at the track. The engine seemed to be running very good, and the 5 cylinder miss was gone, but the vibration was still there. I neglected to mention this to you guys in my first post, since I thought the vibration was surely being caused by the miss.

So, when I got home, I left a message for the mechanic that the vibration was still there. I will have to deal with him on Monday....oh joy.

My question for you guys is do you have any idea what could be causing this vibration? Again, this is a '73 mechanically injected RS Spec 2.7 motor. The vibration is new, developed at the track after the missed shift, I presume. It is less noticable below 2,000 RPM's, but becomes pronounced throughout the RPM range up to red-line. The motor runs good, but this vibration seems to be holding the motor to approximately 80-90% of its original power. Could it be something in the Trans or Clutch? The missed shift was third instead of fifth at approx 120 mph. Seeing that the mechanic did not remove the motor to do the valve work, there was no opportunity for him to inspect the Trans or Clutch, not that he would normally do that anyway.

Sorry for the long post... just feeling a bit depressed about being $2,500 lighter in the wallet and still have 80% of my RS power!!!

Thoughts???

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John
73 911S

Dear friend,i feel for you i have been there before,and for some reason all of us that try to enjoy this cars are always victims of this mother**** ers,on my latest shop visit,i spent around $2,000 for some repairs,500 miles later i have to purchase two new rear tires,have the car re-align,and so on,so my point is that if your problem persist and you have that gut feeling is because something is wrong,which means trying to get it right and look for another shop.so you are not alone in this bad times.....

Is the vibration only there with the clutch under load? If you push in the pedal does it go away even though the engine is reved?

Mackgoo,

The vibration is the same whether the clutch is engaged or not. One thing that occurred to me last night (I haven't checked yet), is whether it could be either a missing/broken transmission or motor mount. Within one lap of the missed shift, I felt like something heavy and rubber bounced off the bottom tub under my seat. It also sounded and felt a little like a backfire through the intake, though, so I didn't think too much about it.

The best description I can give is that it appears to be as if the crank is bent. I am virtually certain that could not be, but it is that sort of out-of-balance condition that I am trying to describe.

Any other ideas?

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John
73 911S

How about at a stand still?

John,

I think you have just experienced what was hoped would be a quick fix, but in fact was just a quick rip-off, intended that way from the start by this so-called 'mechanic,' who has demonstrated his lack of ethics by now!

Was there any discussion of the vibration while he was planning his quick bent-valve fix?

I think a serious discussion of your bill with the owner of the shop is called for, if it is a different person, followed quickly by a visit and discussion with the BBB! Why do I have the feeling there will be a fat complaint/history file on this rip-off artist?

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Warren Hall
1973 911S Targa

Mackgoo,

The car does seem to idle a bit rougher than usual, and definitely vibrates when revved at a standstill.

Warren,

The mechanic (also the shopowner) was at the track when the incident happened. He was well aware of the vibration, but I also think he assumed it was a result of running on 5 cylinders.

I don't know what to do. I think I am going to talk to him tomorrow and tell him that I think he needs to fix this on his dime, or the remainder of un-used dimes I gave him the first time!! He may tell me that he can't do free work, at which point I will have to cut my losses. I live in Kansas City where there are exactly three Porsche mechanics... the one in question, another competitor who screwed up my mechanical injection beyond belief, and the Dealer!

Does anyone have any ideas where I might pinpoint the source of this vibration?

Thanks,

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John
73 911S

John,

I can certainly appreciate your frustration and pain, as I had a similar situation last year with a hospital stay and exploratory surgery that answered no questions about what was wrong, and left me with an irregular midline scar on the belly and a $12.7 K bill above that which insurance paid, that I will be paying off for another year! My trust in doctors was shattered, to say the least!

I am not certain how well anyone can 'suggest' possibilities for the vibration source with anything but guessing, at best. My 'guess' is something to do with the intermediate shaft or cam chain drive, but it's just a hunch.

My best suggestion would be to use a stethoscope around the engine to see if anything can be detected. If it is possible to do the troubleshooting in a closed garage with the exhaust routed out side with flex hose clamped to the muffler outlet, do so! The type of mild steel flex hose I am talking about used to be available at auto part stores, years ago, but I haven't seen any recently.

If possible, put the back end up on jack stands, and be sure to use the stethoscope on the transaxle, too, because you NEVER know, unless you check! I have heard of transmissions being damaged on a missed shift, too, and yours may be one of them! Since the input shaft is turning while the transmission is in neutral and the clutch is released, there are lots of parts in the trans turning over when you run the engine in neutral ... a bearing may have been damaged by the overrev! [Second Guess] Good luck!

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Warren Hall
1973 911S Targa

[This message has been edited by Early_S_Man (edited 10-01-2000).]

Since there are so many guesses flying across this bulletin board, I might as well add mine: How do you know that one and only one valve was bent during the over-rev?

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Bob Thayer
1971 911T
rthayer@hdrinc.com

Stinky,

Not a bad question. The only "assurance" I have is my "mechanics" commentary on the great condition of the "surrounding" cylinders, i.e. numbers 1 and 3. He was trying to "save me some money" ($2,500 for one side), by just checking into the left bank. Supposedly he did a compression check on both sides and only number 2 was suspect.

The vibration that remains does not "feel" like a mis-fire or 5 cylinder running, it feels more like an out-of-balance situation. Again, kind of like rolling a slightly bent rolling pin down the kitchen table really fast.

Thanks for guessing! All ideas are good ideas. Will keep everyone posted as to the outcome of this.

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John
73 911S

Update, but still not right!

Hello friends, I wanted to give a little update since we chatted last and ask you
about my latest dilemma.

Background:
1) Bent valve on number 2 cylinder supposedly repaired by local shop after mechanical overrev at track. Head machined, etc... $2,500.
2) Got the car back, and the miss was gone, but bad vibration persisted.
3) Mechanic pulled the motor to inspect suspect clutch and found that the damper springs in pressure plate were bent. Replaced clutch disc and installed "alloy" pressure plate.

Next: Noticed a lack of power while driving away from the shop, but the bad vibration was gone. Drove it for a couple of days and noticed that there was still a noticable hammering in the left bank of the engine. Also noticed that the car still seemed "heavy"... missing 20 HP or so. Also noticed that a "miss" or "stumble" had re-appeared. Also noticed that my valve covers were leaking onto my exhaust. Needless to say, I was very frustrated. So, refusing to go back to this mechanic, I did some digging myself. Just to keep things in order I will list them below:

1) Looked at my invoice from the mechanic to see what all he had done.
2) Noticed that I got a new set of $120 spark plugs that I had not asked for.
3) Called and asked him about the spark plugs, the left bank hammering, the leaky valve covers and the 20HP loss.
4) Mechanic says not to worry about the "RS" spark plugs, no response about the hammering, but said regarding the power loss, "when we got the valve repaired and compression restored, the engine was running so good that the idle was high. Instead of adjusting the air flow screws in the stacks, we decided to retard timing!!!" That should address your HP loss, he said.
5) Odd, I thought. Why would anyone retard timing to correct idle?
Anyway, I decided to advance the timing to see if it would restore my power.
6) I didn't have a timing light, but noticed that the distributor was turned all the way clockwise to the end of its adjustment slot.
Remembering about where it was before, I moved it just slightly.... 1/8 to 1/4 inch counterclockwise and tightened it back down.
7) The power seemed to get better.
8) In examining my valve cover leak, I got underneath only to notice that my heater hose, and more importantly my mechanical injection hose were completely unhooked!!! Aha, there is my miss! Hooked them back up
and the miss was gone!
9) Everything is good at this point.
10) After driving it for a week or so, there seems to be a roughness to the engine that was not present before. I have since checked the timing with a timing light and set it to 32 degrees BTDC at 6,000 rpm. I would say the car still feels short approximately 20 HP. It almost feels like the cam timing is early or late or something similar. The exhaust makes a bit of a buffeting noise, almost like the bent valve, but not nearly as bad. Basically, it just lacks power and feels as though it is laboring. I refuse to go back to the mechanic, even for free, but am at a bit of a loss for next steps. Any insights would be appreciated. Sorry for the long post, but I enjoy reading details and hoped you would too.

Sincerely,

p.s. The "hammering" in the left bank turned out to be the throttle body shafts rattling due to wear. I.e., the rattle stopped when I grab the shaft lever near the left stacks. (Thanks for the stethoscope tip, Warren!)

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John
73 911S

John,

It sure sounds to me like your shyster mechanic is sloppy, incompetent, and careless, as well as being crooked and a liar!!!

I suspect he messed up your cam timing on the left bank when he did your valve/head repair ... probably did it by eyeball and never even messed with a dial indicator in his haste to get it out the door and to get your $2500 fast as possible!

To check the timing you only need a cheap Chinese indicator from Harbour Freight, and either a 'Z' mount (Pelican) or magnetic mount. Doesn't require getting at the cam sprockets, so don't worry about having to pull the muffler or rear sheet metal. Engine should be cold enough to adjust the valves, remove intake valve cover, turn over engine till at TDC firing point for cyl # 1, position dial indicator on cyl #1 intake valve retainer or convenient point of reference if using 'Z' bracket, and preload indicator 0.4" and zero. Turn oover engine exactly one crankshaft turn to TDC again and you are at the overlap TDC for cyl # 1. Read gauge. It is supposed to be 5.0 to 5.4 mm, 0.197" to 0.213" ... and should be within 0.001" to 0.002" of the reading on cyl # 4, but I am betting it is not, so you may want to order a cam chain cover gasket set and cam holder, pin removal tool, and crowfoot ... just in case! Good luck!

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Warren Hall
1973 911S Targa

[This message has been edited by Early_S_Man (edited 12-07-2000).]

Satisfying to know that Warren is a Harbor Freight customer (my assumption). And yes, we do love details, so thanks.

I concur with your and Warren's assessment of the "mechanic." Just wish I knew enough to help with the diagnosis.

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'83 SC

MY thoughts.The first clue was when you said he didnt remove the engine from the car.

I live in Kansas City as well and would like to know who it was!I'd also like to see this trick of changing the valves without taking the engine out.

Amazing story. I can save you some
money on tools Warren said to get.
The cam pin tool is not needed, it is the same thread as a common spark plug. Use a spark plug instead of buying the cam pin tool.
What about the fellas at ImagineAuto? I thought they were near KC, I would recommend them in a heartbeat. I can not fathom
doing a valve job with the engine in the
car, though I did hydraulic tensioners and
chains once while the engine was in the
car. Never again!

Bill
72T

*** Update ***

I feel like a real slug taking this long to get things sorted out, but I wanted to provide the final chapter to this mishap that has plagued me for the last 6 months.

You may recall that a missed shift in my RS Spec Coupe resulted in a mechanical overrev at a track event. You can read the rest of the history above, but basically after spending $2,400 to repair a supposedly bent valve, and $1,200 to replace a clutch plate with a bent sprint, my car was returned to me with disconnected MFI and heater hoses, stripped distributor hold-down stud, profuse oil leaks from both valve covers and transmission, and worst of all, still missing about 20 horsepower.

Well, vowing to dump that mechanic for good, I dug into things myself. I repaired all of the peripheral things mentioned above, and proceeded to verify the cam timing. Sure enough, on the left hand bank, where the "work" had been done, the cam timing was off by more than 1/2mm!! Not sure if you are aware or not, but that is a lot when we are talking in terms of precision timing and the valves opening and closing at the exact right times. It is enough to make your car feel like one or two plug wires are disconnected!

It is now dialed in correctly, and my RS Spec motor is pulling extremely strong once again. The moral of this story is that you should not implicitly trust your mechanic. They have questionable motives to start with, and are really just interested in getting your wallet to leak.

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John
70/73 RS Spec Coupe

John,

I really appreciate your excellent updates. This has been a very educational story, albeit a very expensive one as well.

I trust very few mechanics. Of course, they overcharge folks, but I am mostly afraid of their incompetence. There are folks on this Board who believe I know quite a bit about cars, and I'm not sure they are correct, but it is rare indeed for me to feel like my car is better off on someone else's hoist. And part of this is my observations of mechanics and their techniques. They are in a hurry and they are not working on their "baby." they are working on YOUR "baby."

Your baby is safest in your hands. John, it sounds like your skills are greater than those of this professional mechanic. And your degree of care and diligence is FAR in excess.

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'83 SC

JANDREWS,

I read your story and hopefully there are better times ahead for your RS....maybe post a pic or 2 so we can all have mental images.

Please do tell us the name of the shop, it might save someone a headache down the road.

If you're in Kansas City, you might try Stephen Kaspar at Imagine Auto (www.imagineauto.com) ... he did some work on my 87 930 last year and he's very well known on the Rennlist. He's in Olathe. He also had a beatiful 72 911 that he did an RS spec motor on, so he's knowledgeable about those cars as well as the turbos that he specializes in now.

Vic
88 Carrera