[thstone]

Thanks for all of the great thoughts! Here are a few responses to some of the questions...

Originally Posted by PaulE

Can you just do races closer to home, or within your AAA towing range until it lets go?

Yes, that is a possibility but I would prefer to maintain the racing schedule based on my racing goals than having to work around a potential engine failure.

Originally Posted by PaulE

Can you assess the likelihood of collateral damage to your car if the engine lets go on the track-eg oil or coolant spill in front of a rear tire that could cause a spin?

Its almost impossible to know what might happen when it finally fails so I'd have to say 50/50.

Originally Posted by jcslocum

Is there a typical failure mode that can be inspected for wear/potential failure?? Maybe with a boroscope? Oil test, etc...

As someone else mentioned, there are 30+ failure modes and only a couple could be inspected.

Originally Posted by 10/10ths

Let her blow up. Fun times. Builds character.

Well stated and right to the point!

Originally Posted by 78F350

For you, I don't see this as a monetary equation. The cost of your replacement engine is insignificant in the balance of what you have spent on preparing the car for the next race day. It is a maintenance item and has completed it's expected service life. My guess is that the more significant cost is the loss of a race day due to a failure that could have been prevented.

Yes, you accurately described the situation. I like your statement about "expected service life", that makes a lot of sense and is a good case for replacement.

Originally Posted by 78F350

So, what do you do with the old engine? I assume that it is still more cost-effective to buy used rather than rebuild. There is a finite number of 2.5s available though. Hopefully there's a shop out there to gather them up as cores and rebuild them for the street.

The old engine could be rebuilt or sold as a core for someone else to rebuild. It is more cost effective to buy used than have professional rebuild but DIY engine rebuild is probably cost competitive.

Originally Posted by 911monty

I lost count, what was Jake up to 36 modes of catastrophic failure? Your replacement engine has about the same probability of failure at any time. Maybe more since it's untested. If current engine shows no significant loss of power then I'd do compression and leakdown and go from there since emperical evidence indicates most fail from some issue long before they wear out. The ones that don't fail run for 300k (Jager anyone?? and how many out there we don't hear about) and definitely skew the data.

My list has 31 failure modes and Jake probably knows of several more that I've never heard of. And you are correct, the replacement engine is a complete unknown but it was running well when it was removed from the donor car so it will run, the question is how long.

Originally Posted by The Radium King

time for a trailer. your track car no longer has to be street legal (you have your targa for that, yes?) the inconvenience of blown engine is reduced. depending on size of trailer and tow vehicle, you could even bring your spare engine with you - lots of guys there willing to help with an engine swap in-situ.

Yes, I use the 911SC Targa as my daily driver; the Boxster is only used for racing (including commuting to/from races). Your suggestion of a truck and trailer is an good solution.

But I have to admit, I really like the romanticism of being able to race a car that is driven to/from the track but maybe that time has come and gone. Something to seriously think about.

Originally Posted by seningen

Assuming you have an off season -- I'd replace it. But, you are replacing with a unknown time bomb if its a junkyard used engine.

Yes, there is a racing break from mid-December to early February which would provide time to do the swap. I don't think of a used engine as a time bomb since it was running perfectly when it was removed from the original car. The question is will it last 40, 60, 80, or 100 hours.

Originally Posted by seningen

Then take the now in-car "used" engine -- and do a rebuild of it so that you have a back-up just in case. I haven't checked in awhile -- but it's probably $2k in parts to rebuild (depending on how crazy you get)

Doing a DIY rebuild is a good idea and would be a fun project. The cost would be competitive with another used engine.

Originally Posted by seningen

What have you experienced in the past as failures? Bearings? Rod bolts? lifters?

My personal experience for 3 engine failures is a failed lifter, failed lifter carrier, and a failed crank bearing. None of those failures released any fluids onto the track.