When to rebuild..
 

I have a 1984 911 with roughly 250k miles. Original engine/trans. It has mostly sat for the past 4-5 years while I played with other toys. But now I have decided to freshen it up over the the winter. It has a few oil leaks that is otherwise running fine. So should I pull the motor and rebuild it or just fix the leaks and keep driving it until it starts smoking or requires a rebuild? I know first things first I should do a compression check but assuming that is OK does anyone rebuild just due to age or wait until its necessary?

Colby

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Well when you fix the oil leaks, with very few exceptions, you DO take the motor out. At that millage I'd be sorely tempted to address a host of other things. Valve guides & seals are the reason many people, myself included drop the motor. Addressing oil leaks is up there too. Then its up to you whether you want to re-ring the bores, address the rod bolts and bearings and of course clutch, etc. My guess is you end up with a full rebuild =)

The oil leaks are from the oil return tubes so those can be accessed from underneath. It is running fine, not smoking, consuming oil, etc. But it is the original motor with a ton of miles. Do high mileage motors just slowly wear out or could something let loose that would be catastrophic? I don't want to blow $10k on an unnecessary rebuild but I don't want to not do a rebuild a destroy the motor later.

Colby

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300K + and it just keeps on running....
 

My 1980sc has over 300,000 miles and the engine has never been opened.
It runs great.
It does not burn any oil and has plenty of power.

I fixed all the oil leaks and replaced all the gaskets, sleeves and O-Rings in the CIS.
I also replaced all dried and cracked hoses.
I did all this work without dropping the engine.

However,
If I had to do it again I would definitely drop the engine and the transmission.
That being said if you rather not drop the engine all the work can be done with the engine in the car.

For what it's worth:
I have the original non pressure fed chain tensioners.
I do not have a pop-off valve and I do not have any broken head studs.

I would not rebuild until the engine gives you a reason. Oil consumption is the usual reason.

-Andy