OCTOBER 2015 QUestions ...

1) Where do Corvair cases/heads/parts come from?  Are they all from the 1960's?  How do you confirm that they are "airworthy.

There are a few ways that we use to confirm the use and airworthiness of a particular corvair engine part.   We will tackle the two parts you mentioned above today.   The majority of the heads and cases are from cars built from 1964 to 1969.  For those building their own engines there is a listing of the model number most appropriate for aircraft use.  We have a list of those in our Teardown Manual

Initial condition:  If you are tearing down an engine core that came from a running engine and/or the engine turns over easily, good compression, and clean, there may be higher odds of finding core parts in good condition.  Once stripped down, you can begin the cleaning of the individual parts and start looking for....

CASE:  Once the case is apart and the engine model code is verified to be usable for the conversion get your cleaning supplies (purple power spray bottle and a stiff britle brush) and begin soaking and cleaning the grime off the case.  I will soak the parts and come back every fifteen minutes and spray down the part for the whole day and toward the end of the day wash the parts off.  This lets the spray soap do its work.   Other options are taking the case to NAPA or similar machine shops and having the case professionally cleaned...  As you clean the case you will notice more about it.  On the case we look for hammered out main bearing saddles (not to typical) and highly scored cam bearing surfaces.  The other thing we look for are damaged lifter bores.   We have run into many cases that have factory repairs, welding or lifter sleeves, but the quality of the work will be good.  If you have concerns shoot us a picture.  We have orginal drawings and dimensions so we can check out bearing saddles for out-of-round and more.   For the most part the cases hold up real well.   Head studs can be bad, bent, corroded and more and we have to remove and replace them. 

HEADS:  On the end of the heads is the casting number.  Verify the appropriate head for the engine you want to build.  We typically use any of the late model 95 HP or 110 HP heads.  However, we have capabilitied here to modify some early heads for custom work and have several engines flying with them.   Again, it is best to dissassemble the heads and valve assemblies for a proper cleaning.  We look very closely at the combustion chamber for any signs of corossion and overheating.  (pitting or deap imprints from the head gaskets)  We usually have to set up our mill and flycut the chamber bores slightly to reset the gasket area.  If the heads are really nice and the seats look good will will normally leave them in place.  If there is any question about the seats we replace the intake seats with deaper seats.  New bronze guides and a three angle valve cut with new stainless valves and springs bring the heads back to good condition.  If requested we also mill off the original carburetor pad and weld on intake pipes for our manifold.   We process lots of heads here at the shop.  It is not a job for the untrained....dont let that stop you from learning though :)


SEPTEMBER 2015 Questions....

Do you recommend regular oil analysis for the Spyder engine?
An oil anysis is typically a situation where you send an oil sample to a lab and they respond with results of amount and types of materials found in the oil.  If the copper content is high it may be a sign of premature bearing wear.  If bronze is high - maybe guide wear and so on.   I have not done these types of tests because I usually open the filter after an oil change and look at the pleats - or wash the material onto a clean paper and look it over.  By running a small magnet over the material you can determine if there is metal wear.  Non-ferous material can be checked by color and type of material.   I find that an analysis will only find something I can spot in the filter inspection.   I dont recomend using oil analysis before the first 100 hours because there is a lot of initial break-in wear that will give you false results.  If you establish a base line and monitor from there then it is a good procedure.  Because of the kind of flying and maintenance I do I don't perform oil analysis on my planes.  One reason is becasue sometimes I change the kind of oil I am using to check cooling and lubrication properties and its hard to have a base line when you change the oil type midstream.

 Is it reasonable to convert the 100HP Spyder to the 120HP version?  Do you have any details/recommendations for such a conversion?

There are some major differences between the two engines, however, it is an easy conversion.  Take the 100 off the mount and bolt the 120 on!   The 120 has a new, counterweighted and stroked crankshaft, new design rods, and new design pistons.  Is is much more cost effective to build a 120 and then swap out.  We will pro rate any of our engines for exchange or come up with a equitable exchange with any customer of ours or even with people changing from a competitor design to ours.   All of the auxiliary or FWF parts are similar between the two engines and don't have to be changed.  What can you expect as part of the exchange?  You will probably have to change out the propeller or change pitch but not absolutely necessary (depending on installation).  Expect that CHT's would be slightly higher on climbouts - however you could get to altitude more quickly and then throttle back to cruise configuration where temps will stabilize.  Any given power setting will give you higher performance however remember that the airplane will perform the same at same RPM (with same prop).