Keeping the Oil in the Engine

This tech tip is based on information and photos supplied by Norman Nock of British Car Specialists in Stockton, California and Malcolm Terry of Marion, Indiana.

Originally published in the Austin-Healey Magazine, January 1990


One of the standard signs of the aging Healey is oil puddles—on the garage floor, driveway, or any other place the car is stopped for more than a few minutes. Most often, that oil is coming from the crankshaft aft of the rear main bearing and/or, in the 100/4s, from the gearbox shaft at the front of the gearbox.


Fig. 1 The spiral groove in good condition

The problem is that British cars of the50's did not use oil seals for the crankshaft and gearbox shaft. The housing that the shaft ran through had a spiral groove in it that was designed to "screw" oil in direction of the spiral as the shaft rotated. The first photograph (fig. 1) shows a scroll, or spiral groove in good condition.


This action moves any oil within the gap between the crankshaft and block forward into the oil return passage in the main bearing cap or rearward back into the transmission. However, this design depends on close tolerances between the shaft and housing. On a new engine, this concept was satisfactory, but who owns a new Healey engine? Over years of driving, the bearings, shaft, and housing wear. increasing the clearance, reducing the return effect, and eventually allowing oil to escape due to gravity and pressure.


Fig. 2 Original gearbox housing and modified housing

There isn't an easy fix to this problem. In the first place, the engine or transmission has to be out of the car, with the crankshaft or gearbox shaft removed. In the second place, the correction requires a good machinist who knows Healeys. It isn't something you would do just for its own sake, but if you are rebuilding the engine and transmission, or have them out of the car for some other reason, it is worth fixing, or insisting that your rebuilder fix this problem by putting an oil seal retainer on the engine and transmission and installing seals.


Top view with seal. Modified housing on left.

In the second picture (fig. 2), Norman Nock shows the original BN1 gearbox front housing and one that has been modified by having a competent machine shop weld a retainer to the housing. The third picture (fig. 3) shows the top view and the oil seal. For seals, Norman recommends Motion Industries#CR10515 or National #9376 which are available at any good parts house.


For the crankshaft. Malcolm Terry uses rear main seals available for big block Chevys. This seal will fit the 100/4 engine block without modification, though the seal does require slight modification of the rear mounting plate to fit the six-cylinder engine block.


Seal and rear mounting plate on six-cylinder block.

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