Saturday, December 25, 2010

Engine decisions

Yesterday, I had a quick mission to load up with cheap gas and then go see the IA at one of the shops I've used at Livermore, MaintenanceXpress.  I tested out the heater again on the way over, and of course it worked just fine.  Also I haven't seen a recurrence of the fuel gauge problem, but Chris thinks it sounds like a fuel sender issue.  For now it's not a safety of flight thing but might be worth overhauling the fuel sender at annual which is coming up in Feb.  On another note, I spent a fair bit of time discussing firewall forward options with Chris.  The metal I found in my oil screen was small and most of the advice I've gotten is to just continue to fly and monitor it, which I have been doing.  Nevertheless, I'm prepping myself for a firewall forward job and looking at various options.  Continental just raised their prices 3%, which puts a factory remanufactured engine just shy of 30k, and of course I have two.  Damn these things are ridiculously overpriced!  Airplane engines are basically big lawn-mower engines for crissakes! 

I could probably save a significant chunk of change going with a shop overhaul, but the issue I have is that it's a bit unclear whether I have the more modern "VAR" crankshaft (Vacuum Arc Remelt), or the older style "Airmelt" crank.  If I have an airmelt crank, Continental won't penalize me for it and will take the engine on exchange for full credit.  A shop doing the overhaul would need to replace the crank and charge me for it.  Replacing the crank would probably eat away any money I would save by going to a shop vs. the factory.  Here is the note I got from TCM.

Hello Adam.
We were able to pull up and check your crankshaft serial numbers.  Engine s/n 215733 was manufactured with a VAR crankshaft.  However, engine s/n 215734 was manufactured with an airmelt (non-VAR) crankshaft. 
There was not a way to verify this with the engine serial numbers alone, so I don't understand the statement made by your local shop.  Factory-Rebuilt IO-520-E engines with serial numbers of 215782 and higher were originally manufactured with VAR crankshafts.  Engines with lower serial numbers must be inspected.  (Confirming the crankshaft serial number is one of the ways to inspect this.  The serial number is imprinted on the flange of some crankshafts.)       
In any case, if you're going to purchase TCM factory engines it doesn't matter.  We will not penalize you for returning engine cores with airmelt crankshafts.
In regard to the core exchange, we'll send the new engines and ask that you return the old engine cores within 90 days.
TCM will not accept your engine cores until the Factory-Rebuilt or New engines have been shipped from our facility.  In any event, having both engines together during the installation is very beneficial to the mechanic(s).  There are quite a few things that must be transferred to the new engine (baffles, probes, exhaust, brackets, fittings, STC items, etc.).  In most cases, when a core is returned before the factory engine is installed, parts are left on it that should've been kept.  And once a core has been processed at the factory, the parts are irretrievable.  I should also mention that all TCM factory engines are packed and shipped in a special crate.  This crate must be returned, or there is a charge of $200 each.

So I'm still not 100% if what he is telling me about the VAR/Airmelt crank is correct, but if it is I could do one factory overhaul and one shop overahaul, or I could just do two factory overhauls.  That plus prop overhauls, various R&R, shipping fees, hoses, baffles, mount etc. and I'm probably looking at north of 80k to do both firewall forward jobs with factory engines.   Maybe 10-15k less if I can get away with shop overhauls.  I just put three new cylinders on the right engine last year so that will also factor into my decision.  I can save some dough to keep those and just overhaul them rather than get new jugs.  Either way that's tough to swallow when we're probably 3-5 years away from viable diesel technology and the future of leaded aviation fuel is unknown.  Decisions, decisions.

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