HEI Conversion

by Paul "Inky05" Yacabitis
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     "HEI" is NOT a Hawaiian greeting. It stands for "High Energy Ignition" and refers to GM electronic ignitions. Just about all GM engines (from the mid-1970's up to the distributor-less era of the 1990's) were equipped with HEI distributors. This HEI is an elegant design, incorporating an electronic ignition module, magnetic trigger device and ignition coil into a single assembly. It delivers a hot spark for easy starting and long spark plug life. In fact, it could fire plugs with up to .060-inch gaps at low rpm.

      "Inky05" is not a new Stovebolter who's really jumped into the action. A welcome addition to the Stovebolt Collective ~~ Editor

HEI Conversion
How hard can it be?

Believe it or not, its easier than you might think.

      First off, you need to find a donor. The bone yards are full of early 1980's vintage Chevy's, many of which were powered by the ever-abundant 250 six cylinder. A distributor from one of these can be had quite cheaply, and is easily modified to fit your truck's 216 or 235 power plant. The GM "HEI" distributors have a coil integrated into the cap, making the wiring simple enough for the average five year old to accomplish successfully.

      Be sure to take the "hold down clamp" from the donor along with your "new" distributor. You will need it as well.

      It is important to note that the oil pump in a Chevrolet six cylinder engine is driven by a tang at the base of the distributor gear. This tang must engage the oil pump in order for the pump to deliver lubrication to the engine. Upon first inspection of the donor distributor, it may appear to be a "drop in" replacement, and the gear will engage enough to turn the rotor. However, the tang at the base will not engage the oil pump…

Modifications are necessary!

      The shoulder on the distributor housing needs to be removed in order to allow the distributor to enter far enough into the block to engage the oil pump. Although this may seem slightly intimidating, it can be easily accomplished with a coarse file in just a few minutes.

      Now that the shoulder has been removed, you need to make a new one for the distributor to seat against in the proper position. A simple split collar clamped around the distributor housing will suffice. It should be clamped in order to let the distributor go about 3/16" further into the block than the original shoulder would allow. The "hold down clamp" that you got with the distributor can now be used to clamp on top of the split collar.

      Once you have your "new" HEI installed, you should double check to make sure that you do, in fact, have oil pressure.

      Now get out that timing light and set it up right.  Oh yeah, be sure to hook the vacuum line up to the advance.

Paul Yacabitis
Bolter # 6793
N.E. Pennsylvania

"It's not that I haven't done it ... It's that I haven't done it yet..."

v. December 2005

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