Wednesday, February 3, 2010

Solved! - A Standard Engine for Homwbuilts

The final piece of the puzzle fell into place when DuraFix altered the alloy of their aluminum brazing rod. The new rod allows us to apply the Fat Fin modification without fear that the extended fins would crack

For those who have not followed the development of this engine, it' specs are as follows:

2332cc displacement (142cid). That is, a perfectly 'square' engine having a bore AND stroke of 84mm. Rod length is 142mm (5.6"). Compression ratio is 8.5:1.

( - 13 February 2010 -
My thanks to the several of you who caught this error. The 'square' engine would b 84 x 84... or perhaps 94x94... but it would NOT be 84x94. [My interpretation of the Standard Engine is one having a Bore of 94mm and a Stroke of 84mm.] So please accept my apology for this gross mis-statement of fact, for which I've no excuse... although I may be able to come up with one, given enough time :-)

The propeller is installed on the clutch-end of the crankshaft. You may fabricate the required spool & propeller hub yourself using the dimensioned drawings contained in the HVX Files or you may purchase them from Great Plains Aircraft Supply Co (GPASCo).

A 20A. alternator is installed coaxially on the pulley hub. The guts of the alternator are taken from a Harley-Davidson motorcycle. A kit of parts, including the required regulator, is available from GPASCo.

The engine conversion includes the HVX modifications. A swaging tool for installing the Toyota valve seals may be fabricated from the drawings or purchased from Mike Sample.

There are a wide variety of carburetors that will work with this engine. Least expensive is the Tillotson Model-X whereas most convenient is probably one offered by GPASCo.

The engine uses either single- or dual-port heads and may use either single or dual ignition. Unless dual ignition is required by local authorities, single ignition is recommended.

The lightest and least expensive ignition system is the stock Volkswagen system based on a mechanical-advance distributor (ie, the -009). This system uses regular ignition points which should be replaced every 100 hours. The system my be improved by eliminating the points using a solid-state points replacement module, or converted to a Waste Spark system using the CompuFire DIS-IX, although the latter is significantly heavier and about 4x more expensive.


The above defines the basic engine. Engines of other configurations will work but the key factor is overcoming the Volkswagens inherent thermal limitation as dictated by the fin-area of the cylinder heads. The 'Fat-Fin' modification provides an elegant solution to the thermal limitation by increasing the fin area.

-2 February 2010