Getting Started in 2013, Part #10, Piston and Cylinder options.


Reviewing the options to this point, I want to bring the comparison up to the point where every engine has a 5th bearing on it.  These 5 paths present proven options for builders to follow, Again, there are options for each of the five, but this is easier to keep track of with the numbering system. Right now, Phil Maxson has worked out a spread sheet and is keeping up with the series, but at this point I would still like to keep builders focused on the discussion here. We can resort to a spread sheet when we get a lot more information to juggle.

The Traditional terms we use to describe stages of completion are “Closed case”, where the 5 engines are to this point. “Short Block”, which is a closed case with pistons rods and cylinders installed, and “Long Block”, which is taking it one step further by putting the heads on. In the articles so far I have used the term “short block”  because I intend to take each of the five through that stage of completion in the discussion. Our DVD series aligns with these stages. Engine build #1 is the case closed, #2 is the pistons and cylinders, #3 is getting the heads on.

Engine options with 5th bearings:

Allan Able = $2,062

Bob Baker = $2,516

Chas, Charlie = $2,770

Davie Dog = $4,270

Eddie Easy = $3,157 


We are going to look at three piston and cylinder options and then apply each of them to each of the Closed Case systems above. That will give us 15 basic engine build paths.

Notice how the options expand geometrically as we get a little further along. 15 is actually something of a simplification, as I am not going to get into outdated displacements like 88mm, 90.5mm and 94mm bores. Don’t let the expanding possibilities overwhelm you. First and foremost, remember that it is the Corvair being adjustable to fit your exact needs. I am going to use the numbering system to make an easy to see, logical decision path, and I am going to highlight some common combinations like Allan Able building a .030″ over engine and Davie Dog  opting for a 3,000cc displacement.

Yes, other engines come with options, The Rotax 912 comes in the 80hp 100hp and Fuel injected models. In Industry slang, these very expensive engines have nick names. 80hp = “Trust fund kid”, 100hp “Hedge fund Mgr.” and the Injected motor is “MMG” (more money than God). Obviously Rotax’s pricing isn’t really aimed at keeping homebuilding within reach of working Americans.

If you think their pricing is steep, you need to get a look at the typical cost of maintenance repair and overhaul to really understand why I refer to these things as ‘disposable appliances.’ There will be a Rotax ower who reads this, who will write in to tell me that I am all wrong about this, that he is very happy with his 912 engine on his $134,000 imported European S-LSA plane. To him and his budget, it is a great motor because all he wants out of it is that it is an acceptable appliance. He isn’t interested in learning anything about it nor working on it. It is a good match for his shallow needs, and he has the required bank roll. On the other hand, a typical homebuilder, a guy who wants to learn build and fly, a guy who got into homebuilding to get his hands dirty, will find the exact same 912 and the ‘support’ system for it aimed at pleasing wealthy appliance owners, a very frustrating proposition.-ww

Here is the number system for the next stage of engine building:


Piston and rod group (1300)

1300- Piston set with wrist pins

1301- Ring set

1302- Connecting rods  -6-


 Cylinder group (1400)

1400- Cylinders -6-

1401- Base gaskets -6-

1402- Head gasket set


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