Conversion - T2 Huggins

Rev - Nov 11, 2017

 By Jan Zumwalt (EAA #66327)

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Many alternative VW conversions have been tried over the years. One of the most popular conversions in the 1960-1980 period was the Huggins conversion. Many of it's features can now be recognized on modern conversions.


The Huggins conversion used either the stock crankshaft (no modification required) or a custom tapered crankshaft. If a tapered crankshaft was going to be used, the case required machining.

/data/content/menu-conversions/huggins/vw_mag_mount.pngCylinders & Heads

As part of the Huggins Conversion, rework of the VW engine was necessary so it will accept Corvair cylinders and pistons. The job is really simple if you have a good machinist who is also a sympathetic friend. His first task is to counter bore the crankcase to receive the base of the Corvair cylinders. The cylinder heads received the same treatment so that they would accept the tops of the new larger cylinders. Other internal changes in the engine were the reaming of the bronze bushings in the VW connecting rods to match the Corvair piston pins, and installing new valves and longer push rods. All other changes were external and minor in nature. And, as a final touch, a heavy duty oil pump was installed.. . just to be sure.

Note: In the early 60's thru late 70's there was a lack of big bore after market cylinders and pistons for the VW and so the Huggins conversion used Corvair cylinder & piston parts. Now days, there are inexpensive big bore parts specifically designed for VW use. JE, AA Performance Products, and SCAT, are just a few of the popular manufactures of big bore "stroker" parts.

Oil Leak At The Prop Hub

Any oil leak is annoying but one at the propeller hub is especially messy. An oil leak at the hub may be caused by an improperly installed slinger ring or one poorly modified. Taper shaft engines such as the Huggins conversion require the retention and use of a modified VW slinger ring. The standard modification consists of 6 saw cuts spaced around the inside circumference of the slinger ring. Properly done, this creates three equally spaced metal tabs that must be bent inwardly at least 1/8". The purpose of the tabs is to wedge the slinger ring firmly between the shoulder of the crankshaft and the aft side of the propeller hub. Such an arrangement properly executed insures that the oil slinger will turn with the crankshaft and the propeller hub.

Some modification drawings indicate that the tabs need only to be bent in as little as 1/16"... this may not be enough to cause the slinger to be wedged sufficiently so that it does turn with the engine. Much depends on how deeply your propeller hub penetrates.

Should you have an oil leak that could be attributed to such a condition you might be able to correct the problem without a complete engine teardown.

In one case, we were able to effect a fix without any disassembly other than the removal of the propeller hub. After the hub was removed, it was found possible to reach in and bend the tabs a hit more. To accomplish this feat, two small screw drivers were inserted into the saw cuts, one on each side of a tab, and pried apart causing the tab to be bent forward. This was done equally to each of the three tabs. The net effect apparently was sufficient to correct the problem oil leak.

Oil Leak At The Crankcase Oil Seal

The large black rubber-like oil seal that is pressed into the counter bore around the flywheel center is supposed to prevent oil leaks. Most of the time the seal does. However, there are two builders who learned that sometimes it does not. One builder who had a chronic leak found that the spring-like wire inside the seal apparently was too loose. He twisted it a bit making it fit tighter around the inner lip of the seal. This cured his problem.

Another builder bothered by an oil leak from the aft end of the engine removed his seal to investigate and found that the internal spring-like coil was missing from his seal. It had been a newly purchased seal but the builder did not know that the coiled wire was missing from it. A new seal solved his difficulty. (Oh, yes, he did not get a refund on the other one although he tried.)