A Second Crank Opinion

Special update!

I told Bruce Lindstrand what I found in the engine. He called his engine builder, Curtis Farley, and before Bruce had finished saying, “Low oil pressure,” Curtis told him that the #3 main bearing was pounded out. A clever deduction indeed, 007, but why? Mr. Farley outlined the three likely scenarios.

#1: Motor Mount Strain. The Ford “Kent” engine has motor mounts on either side of the block. If the frame of the car is crooked (all racecar frames are after a while), the engine will not be perfectly centered in the frame. Forcing the motor mounts into position can put a strain on the engine block, and the strain can be severe enough to actually twist or bend the block. I know we can rule this one out. We’ve pulled and reinstalled the engine about half a dozen times, and by the second time we learned the proper technique. You don’t record how many washers were on which engine mount and then force everything back into the same position. Instead, you loosely assemble the engine mounts, install the gearbox, and gradually and evenly tighten everything down. Eventually, the chassis and engine combination will “tell” you how many washers go where. Everything gets centered as well as possible, and strain is minimized.

#2: Insufficient Oil Supply. The Kent engine has an odd oil gallery design. The oil pump feeds into the right side of the block, but the oil has to pass to the left side of the block before it goes to the main bearings. The gallery which feeds the #3 main is notorious for being too narrow and is easily clogged by debris. You could say the engine has a heart attack. The good thing about this scenario is that it is easily fixed. A threaded plug on each side of the engine block can be removed so that you can look through this passage. Any blockage will be obvious and easy to remove, and the oil passage can be drilled out to allow more oil flow. The oil pump plumbing can also be rearranged to feed the main bearings more directly, but that may be a bit extreme.

#3: The “Mystery of the Collapsing #3 Bearing.” The story goes that every once in a while, despite meticulous assembly, a Formula Ford motor never develops oil pressure (or else the oil pressure quickly drops). Everything checks out, but the #3 main bearing is trash. If this condition is found before the engine is run, it may only need new main bearings to live a long and happy life. Nobody knows what causes the bearing to collapse, or why the replacement rarely fails. Although the fix does not involve any machine work, I don’t like this scenario at all. I’d much rather be able to positively identify the cause of a problem and take steps to prevent it from happening again.

Unfortunately, his professional opinion is that reusing the crank would be a bad gamble. Bending the crank has weakened it. Even if the machine shop could regrind it to compensate instead of bending it back into shape, it is still not likely to stay in one piece.