Lessons learned?: Buying a "used low mileage engine"....

[Brian Porsche Tech]

After reading this entire story across both threads on my day off, I feel obligated to point out several things that don't add up.

As others have said, buying any used engine is a complete crap shoot, and the only way I would ever buy a used engine is if I were planning to rebuild it. I'd say BUYER BEWARE in full caps! 95% of the people who will sell you a used engine will not give you a warranty, and if you get screwed, well you got screwed and have zero recourse. The only way you'd have any recourse is if the engine was stolen. Remember, factory Porsche motors come with a 2 year unlimited mileage warranty!

To whoever suggested that anyone wanting to verify the history of a used engine lookup the VIN #, that's excellent advice, but remember that carfax will only tell you so much. Also, you won't be able to get the VIN from the engine case #. If you are buying a used engine from the guy who took it out of his car, you can certainly talk to him and ask him to contact Porsche to release service records for the car. However, there is no way that you will be able to lookup the history unless you are the legal owner of the car. You can't just call PCNA or any Porsche dealer and say "hey, I'm looking at buying engine case number bla di bla, can you tell me the service history?" as Porsche and their dealers have a strict policy of only releasing information to the legal owner of the car. More than likely you'll never be able to get this info, and if you get a buddy to break the rules at a dealer, he risks being fired for doing that for you, so I wouldn't even think to ask that kind of favor.

Now, with respect to this story, there are several things that don't add up. First, it doesn't matter if the engine has 20k or 60k, if you got less than 3% leakdown, especially cold, you've got an excellent engine. These engines don't wear out their bearings, and if you're replacing the IMS bearing, which is the one big weak leak, anyway it's really a moot point.

It's not surprising at all that the cam timing was off. I made the same goof myself at work years ago when we replaced a head on one of these, as the service manual leaves out a critical step when setting the timing. Was rather frustrating to have to go re-do all that work! All the techs that I know have added notes to the service manuals for things like this now.

Now, the claim that the head bolts were torqued to 10 lbs, this is practically impossible. First, you're not supposed to use a torque wrench backwards! Even if you did, backout torque is not indicative of anything when referencing tightening torque. If whatever "idiot" that built this motor got as far as getting the case halves and bearing carrier, and reciprocating assembly back together I'd say he's no idiot. If he torqued the head bolts to 10 lbs, what do you think he did with the rod bolts and bearing carrier bolts? I'd say anyone who got this far is at least reasonably mechanically inclined and would understand the importance of following recommended torque spec during assembly.

Second, if the head bolts really were torqued to 10 lbs, that engine would have had a leaking head gasket within the first 10 seconds after initial fire up, with all of the usual symptoms of exhaust gas in the coolant and oil/ coolant intermix. There is absolutely no way that that engine would last multiple hours over several days on an engine dyno, and then during street driving, only to leak when first on the track.

Likewise, if the engine had a cracked head, you'd also have oil/coolant intermix immediately after startup on the dyno, and certainly during street driving. If the engine was torn down with a cracked head, then it happened on the track, not before. Let's get our stories straight here folks, and not throw blame on someone where it's not deserved.

By the way, to whatever shop claims to have an engine dyno for M96 engines, what setup are you running, and how are you able to accommodate the various 2.5, 2.7, 3.2, 3.4, 3.6, 3.8 engines with variocam and variocam plus, across 5.2, 7.2 7.8 and 7.8X DMEs and their associated maps? How have you gotten all these DMEs to function without their matching immobilizers? I don't know how you'd get data anyway, since the PST2 or PIWIS (if you have either) will not work without the CAN bus present.