Was I lugging it?

[poorshe911]

My extremely well maintained '83 SC has a bad wrist pin at 81K miles.
Isn't it way too premature of a failure?
Car had Mobil 1 since it was a baby. Was that the problem?
No over heat issues. Leak-down was great .. 5-7%
I was always careful not to lug it but .. what do you guy's consider lugging these cars?

I'm just trying to make some sense out of this failure.

Thanks

[redstrosekNic]

I try to keep the revs over 2800 rpm at all times. Sometimes it is hard to do this in a slow turn, when I don't want to harm the 915 by putting it into 1st. In that case, I accelerate super super gently.

One should also make sure to keep the revs under 3k until the oil is nice and warm.

[RSTarga]

I would think lugging would be harder on the bearings at the crank end not the wrist pins.

[lucittm]

What is a "bad wrist pin"? Are you referring to the bearing at the top of one of the connecting rods? Or is it the fit in the piston? Why is it bad? Has the bearing failed? Is the surface on the wrist pin worn past maximum specifications? What is the condition of the connecting rod?

There could be one simple reason for this or many depending on the visual conditions, measured values, the color of the components and the smell (signifying an over-heated condition). What number cylinder is this? Did you check the oil squirter? Many more questions like this arise when you ask "is it way too premature?"

Mark

[Flieger]

I second that. How do you know there is a problem with the wrist pin/bearing assembly?

[Drisump]

Can't say that I agree that the term "lugging" can be given at a specific RPM. These are very torquey engines and the car is quite light. In my opinion, if the car is breezing along with light throttle pressure, you're good to go. If you are down in the RPM range all the time though, you'll likely need an "Italian tune-up" periodically. Being in fourth and trying to accelerate hard from 30 MPH, now that's lugging. Cheers

[E Sully]

Could a blocked piston squirter cause this?

[poorshe911]

I had the wrist pin symptom verified by two places by very good mechanics. A stethoscope shows cylinder 4 to be the one with the rattle around 2800 RPM's and the noise goes away when the spark plug wire is removed.
Rebuilding over the winter.

[Flieger]

That sounds like a test for an exhaust leak. The greatest stress on the wrist pin in a normally aspirated engine generally occurs on the exhaust stroke when the piston is 'flung over the top'. Anyway, I don't think lugging it would make the wrist pin bad.

[ant7]

Hi,
Could also be a rocker shaft ???
Anthony.

[Brorag]

I keep the rpm's above 2K.