Say it isn't so... (long)

[Ho Hum 74]

After 3 months of blood sweat and tears my '74 Carrera 2.7 MFI made it onto a track at Grattan Raceway in Michigan. I was so excited about having my first 911 on the track (previously tracked my M3 a bit).

The car drove the whole 200 miles there perfectly, only one glitch was filling up my tank too much and having some fuel p1ss out onto the floor.

I was in the first session of the day on Saturday. We went out and did about 10 laps. The car was incredibly strong. Grattan is a great track with about 6 blind apexes and elevation change and a jump for good measure. Abot the 10th lap we come down the main straight and I start hearing a loud tapping sound from my engine. Round turn one and two, give the exit sign and pull in. Get out the car and check the engine bay. Hold on, where's my oil cap? We find it sitting on the engine shroud, whew! So that's what the tapping sound is. Put the oil cap back on and the tapping remains. So we decide that the session is toast.

We take the car to the pit and call one of the on-duty mechanics. It's a BMW event so the guy was more tuned to BMWs but he's known to be a bit of a mechanical genious and actually services some 911s. He says that he thinks it's a broken rocker arm, spring or worse, a main bearing failure. Definitely a metal-to-metal sound. Ouch. I remove the valve covers for him to inspect. He goes though all the valves. "Your #1 cylinder intake valve's a little tight he says". How can he see that? We turn the engine over manually. He pokes his head up and says everything looks fine, could be a main bearing failure. How's your oil pressure? I tell him I've only had the car 3 months and it's always been lowish. If I'm at 3000 rpm it reads between 20 and 60. Is that low? I'm not sure. What is normal? I'm not sure if all the guages work well in the car either.

So after I put back the covers I start the car up again. Now here's the weird part: The tapping is not constant. If it was a piston hitting a valve then it would do it every time. Instead of tap tap tap tap it is tap...pause..tap tap...tap... etc. Until the RPM gets higher. After more investigation it seems like the sound is comming from the rear of the engine. There are belts there that drive the MFI and what else, I don't know. Oh well, my weekend is a total loss. I decide not to take it out again.

There are a few good sides to this: My very good friend insists that I drive his 325i on the track for the weekend. It was a total blast. Kept my mind off things. Another stranger from the club offers to trailer my car to my mechanic in Chicago. He's from Iowa! What an awesome guy. I drove his M3 home.

So the car's at my mechanic. My questions:

1. What is a healthy oil pressure?
2. Could I have some debris (marble), nut or other caught in the back side of the engine and the belts are picking it up?
3. Am I delusional and I'm probably looking at a total re-build?

Diagnosis should be this week. Hold thumbs.

Tristan

[silverc4s]

Tristan,
We will all be anxiously awaiting the compression & leakdown results. Here's hoping it's a minor glitch.

Was your 2.7 recently apart? You mentioned the low oil pressure, 20 to 60 psi @ 3000 rpm is not necessarily low. 20 psi is certainly low at that speed, it should be between 40 and 60 psi in the running range in my experience, at least. What oil have you been using? What filter? Do you have a front cooler? What type? What was your oil temp getting to on the track? Was it a pretty hot day? Boy! I ask a lot of questions don't I? Sorry, just curious about the development of your problem.

Cheers!

[Ho Hum 74]

Bill,

Thanks for the concern. The engine was rebuilt in 2000 to RS spec but the owner never fitted an oil cooler. I just put the front oil cooler in (Mocal 70 row with Aeroquip 12AN lines and Mocal thermostat) and replaced the oil with Mobil 1. Car was running below 180 on the track. Ran at 120 on the highway (low?). Pressure always seemed to be like 20 for 2000 revs 40 for 4000 etc. Track temps were in the low 70s.

Anxiously awaiting mechanic's call.

Tristan

[Ho Hum 74]

Got the call

OK, diagnosis is in. Not good I’m afraid. My car has either had a main bearing or rod failure. Engine has to be removed, torn down and inspected. My first taste of the 911 world has been painful.

At least it’s in good hands. Will keep you posted as to the progress.

[MotoSook]

Tristan,

The rule of thumb for oil pressure is 10-15 psi per 1000 RPM [or more commonly spoken of, 1 bar (14.5 psi)/1000rpm]. Sounds like your oil pressure is fine. On your rebuilt motor you should get at least 1bar/1000RPM.

Your oil temp seems to be a bit low. 120F on the highway is too low me thinks. But I'v never driven an RS Spec motor...sigh! Could be that your front cooler is doing a fine job, but your external t-stat should stay closed until 180F or higher, slightly.

You'll have to describe the ticking with more details. Valve noise is not too uncommon. Where exactly is it coming from? Chain housing? Valve cover..piston position? Top? Bottom?

Hope you get good news from the wrench.

Oh..and why aren't you doing the wrtenching yourSELF! Come on man...

[MotoSook]

You beat me to the post!

Damn..that sounds painful...sorry..who rebuilt the motor? Seems a bit premature for that failure...unless the PO ran hot a lot or the rebuilder cut corners..PO cut cost...

Where is the car now (shop?).

[Ho Hum 74]

Souk,

There's a good chance the car ran hot after the rebuild as there was no external oil cooler fitted. I'd rather not go into why I still bought the car...a bit of bad move on my behalf. The guy I bought it from ended up to be the kind of guy who would cut corners. Ironically I was tempted by the RS engine in such a light car. It felt so awesome on the track.

Car's at Fischer Motors in Barrington. I'd say I'm done until next year. I was so looking forward to Road America in October. Damn.

Tristan

[MotoSook]

Fischer has a good reputation. (no personal experience)

Good luck and keep us posted.

[silverc4s]

Tristan,
The diagnosis fits the symptoms. Sorry to hear this so early in the engine's life. Positive spin: the rods / crank / pistons / valves, etc are likely not damaged, so the rebuild can be focused on the bottom end.

I hope it works out well for you. ;-)

[Wayne 962]

Originally posted by Ho Hum 74
Got the call

OK, diagnosis is in. Not good I’m afraid. My car has either had a main bearing or rod failure. Engine has to be removed, torn down and inspected. My first taste of the 911 world has been painful.

At least it’s in good hands. Will keep you posted as to the progress.

Hmm, I'm a bit suspicious. I don't know how you would ever be able to make this diagnosis until you tore it apart. Be aware of the overzealous mechanic looking for the engine rebuild. I wouldn't take their word on it. There's no way any reputable mechanic would make this statement without tearing it apart first...

-Wayne

[silverc4s]

Isn't that what they are recommending???

[silverc4s]

Wayne - Agreed, but isn't that what the shop is recommending???

Edit> Sorry, I gues I am stuttering today!!!

[Wayne 962]

He said he was told "My car has either had a main bearing or rod failure."

There's no way they could tell without tearing it apart, so they can't make such a blanket statement. I would guess this needs a bit more investigation - unless you really want to part with $10K...

-Wayne

[silverc4s]

Wayne,
I really want to get your point here; this is an area that I have personally overreacted in in the past.

Are there some additional things that should be checked before tearing the engine down? If it is making these kinds of noises, any added running time would cause potentially greater internal distress, right?

What to do next??

[Ho Hum 74]

Wayne,

Good input. I believe that's exactly what they're going to do. Take it out and take a look. I maybe wrote it down wrong in the post that they were definitive. Definitely he said it could be anything but it sounded like a piston hitting a valve and that he'd have to take it apart to see. He mentioned that it could be a number of things and that's when the main bearing / rod failure came up. Then after that info is discovered we'll decide what to do moving forward.

These people have been good to me so far and everyone I talk to in the PCA in Chicago assure me that they are expert and trustworthy folks. Plus they are enthusiasts, not pure businessmen and have a long line of cars waiting so I don't think they're just after my $$.

Tristan

[Early_S_Man]

Tristan,

I, too, am skeptical of such a quick diagnosis ... main bearings don't usually knock, and rod bearing knocks aren't intermittent! My suspicion is valve train problem ... rocker shaft loose and working 'out' ... broken valve spring, rocker adjuster loose/broken, etc.

My suggestion, since you have already decided the car is lost for the rest of the year ... is to have the car trailered home, and do the investigation work and disassembly work yourself! Take your time. Get the factory manuals, both of Wayne's books ... ~ $400 or so, another $500 in tools, and begin the learning process about your engine and car! It will be a much more comfortable process than waiting for more and more expensive phone calls!

The only thing you have to gain is experience, knowledge, and confidence ... at the cost of your own time! The members on the board can assist in your learning process, too!

[Ho Hum 74]

Warren,

That's a good suggestion and I'd love nothing more than to build my own engine. I stripped down and rebuilt a Beetle engine once and it was a lot of fun. My problem is that I already have spent so much time on this car, time away from my family and to put them through an engine re-build would be tough. Plus, I travel every week so I would only have 1 or 2 nights a week to do it. I agree I would learn a lot from the experience.

Tristan

[Rot 911]

How about investing in a auto stethescope (spelling?) and at least try to find out if the knocking is coming from the top or bottom end.

[HarryD]

Originally posted by Ho Hum 74
Warren,

That's a good suggestion and I'd love nothing more than to build my own engine. I stripped down and rebuilt a Beetle engine once and it was a lot of fun. My problem is that I already have spent so much time on this car, time away from my family and to put them through an engine re-build would be tough. Plus, I travel every week so I would only have 1 or 2 nights a week to do it. I agree I would learn a lot from the experience.

Tristan

Tristan,

I feel your pain. When I was contemplating a rebuild, I orginally wanted to DIY but due to job and family needs, I hired it out. Don;t feel bad if that is the right choice for you. However, before you commit to a rebuild, be sure you have verified that something simpler is not needed. You or your wrench can do this.

[MotoSook]

We have a lot of wrench turning Pelicans in the Chicago Burbs Tristan!

I would do as Warren suggested. It can't hurt..hell..you may get the car on the road sooner than you think too!