Questions and Answers
Trying To Get His Bearings
Q. I guess I'm confused on the location of the thrust-bearing. I thought this was a crankshaft bearing. Is it located in the middle or on the end of the crank? I have a couple of rebuild manuals, but I guess I'm still confused. In the specs charts on tightening main bearings, it will say thrust on number seven or whichever for various engines. I don't think I've seen an engine with seven main bearings. So how are they counting the seven. Do they just start at the front of the crank and count both rod and main-caps till they get to seven, and that's where the thrust bearing is? I'm mixed-up somehow. It doesn't matter what type engine, some say thrust on number 2, some number 5, or some number 7, so how are they counting, from which end? I hope what I asked wasn't too confusing.
Thanks,
J.D.A. That's a good question to ask, sometimes there is confusion about it.
Let's start by defining some of these terms. A connecting rod bearing is just that, the bearing between the connecting rods and the crankshaft. A main bearing is the bearing that goes between the crankshaft and the block. The thrust bearing is a bearing that limits the back and forth play of the crankshaft.
Typically, a four cylinder engine will have five main bearings. One on each end and one between connecting rods. An inline six cylinder engine will have seven, in the same arrangement. A V6 engine will have four main bearings and a V8 engine will have five.
The thrust bearing is a special main bearing that is usually installed towards the middle of the crankshaft. In the V6 engine diagram, you'll see that the second main bearing from the front is the thrust bearing. In the V8 engine diagram, it is the rear bearing. Now this does change from manufacturer to manufacturer, and engine to engine. Sometimes it's in the front, sometimes in the back or the middle. It depends on the situation and where the engineers feel it will be best. That's where you're getting confused.
