Solving Delco Main Bearing Problems

| October/November 1991

  • Old Delco bearing
    On left, old Delco bearing with inner and outer races. On right, new bearing with inner race and new doughnut filler bushing.

  • Old Delco bearing

4001 Fox Run Road, Powhatan, Virginia 23139

I have several Delco one cylinder, 32-volt light plants which I have been wanting to restore. They all seem to have a common problem with the main bearings. Invariably, the ones I have found have been discarded and exposed to the weather for many years, and of course, have filled with rain water. This, I have found, seems to enter the engine and follow the valve stems down to the crankcase, settling beneath the oil and building usually to a depth equal to or greater than the main bearings. At this point some water and oil may seep outside around the main bearings, but by now the damage has been done. The steel roller bearings are almost always pitted and ruined beyond use, and the worst part is that the races or bearings are no longer available today.

So, after some time looking at all these engines with their parts lying about, an idea struck me. Why not use a different bearing (heavy enough to carry the load, but not physically smaller), and construct a doughnut spacer of steel to make up the difference in size of the outer race? After checking again with National Bearing in Richmond, Virginia, I found an inner race which fit the shaft, with the same width as the old bearing. All I needed to do now, was machine a doughnut filler to replace the outer race and to make up the difference in size. Then, I allowed five additional thousandths in diameter for a snug fit in the end bell. (See photo).

Well, I picked up the bearings and inner race, made the spacer, and I'm happy to say that this worked well and solved the problem. The Delco engines are finally going back together again, at least until the next problem arises!

This technique of adapting bearings by using spacers might prove useful on other machinery as well. If you need to order the bearings mentioned above, I purchased mine from American Bearing, (804) 353-4407. The part numbers are: bearing HRBC SRF55 and inner race HRBC IR 7275C.