top of page

Engine Restoration - Part 1

Updated: Jul 19, 2022

The Simplex, Crane model 5 engine is extremely large and heavy. Our team designed and fabricated a portable engine stand that could rotate the engine a full 360 degrees using a chain drive gear reduction.



The first steps of our restoration of the engine were to clean the oil pan and crank case. Our shop has a large commercial bead blast cabinet. We did not feel that it was appropriate to use the bead blaster on any interior engine compartment or component. Therefore it was necessary to clean all these areas with solvents and a wide variety of brushes and air tools. Since this engine has a full pressure oil system, it has an elaborate system of interior oil passage. All of these passages required careful and thorough cleaning.


The engine oil pan after initial cleaning and inspection

The pan after completion of cleaning

Since older cast aluminum has a tendency to be very porous we decided to coat the interior. We used Glyptal as it is impervious to oil and it improves circulation of engine lubricant.

Exterior of engine oil pan after restoration

Picture with crank shaft still in place


After removing all six pistons, connecting rods and connecting rod caps we then removed the three main bearing caps. As mentioned before, nearly every part on a Simplex automobile engine and drive train is stamped with numbers from the factory. As an example, each connecting rod cap, main bearing cap, their bolts and nuts were stamped to assure exact reassembly.

After removing and cleaning the crank shaft we found it to be in extra fine condition and it required only polishing, no more than two thousandth of an inch was removed on any surface. A Simplex Crane crank shaft is made from the highest quality forged steel and is constructed in sections, pressed and pinned together. The bearing babbitt was in amazing condition. All the outside diameters of the crank shaft journals were carefully measured with a quality micrometer. After cleaning, the main bearing caps and the rod bearing caps were bolted back in place. A telescoping bore gauge was used to measure the inside diameter of each. After all measurements were taken, each cap was surfaced by polishing them on a thick sheet of plate glass which was covered with abrasive cloth. After polishing, each cap was torqued in place and the inside diameter was re-checked. Once the inside diameter was small enough we could then resize the babbitt, scraping it by hand to less than one thousandth of an inch clearance. Later, proper main bearing and rod bearing clearance would be achieved by "running in" the engine.


A main bearing cap during refitting

Hand scraping the babbitt was a delicate and tedious process


After the crank case was thoroughly cleaned the inside and outside diameter of the camshaft bearings were measured and found to have little or no wear. Also, the height of the intake and exhaust cams was measured and found to be within tolerance. The camshaft was then sent out for polishing.


The camshaft after polishing

Camshaft showing the oil pump drive gear

142 views0 comments

Recent Posts

See All
bottom of page