The Stovebolt Site Forums The Shop Area Engine Shop Knocking noise

I have a 216 motor in my 49 p/u and think it's original. Now that I got it on the road, I noticed that the engine starts knocking loudly especailly after it gets hot. It will overheat a little and spit out some coolant and I have a pin hole leak at the top of the radiator at the filler neck. I'm really concerned about the oil pressure. When cool, it will be just above 15 psi. I have a 30 psi gauge. When hot, the pressure will fluctuate from there and then drop out almost down to zero especially when I'm stopped at a light. The temp. generally stays about 180 but will go up when the oil pressure drops out. The engine does not smoke or use oil and no antifreeze is in the oil. This knocking sound is really loud and I worried about losing the engine. How bad is it???

Sounds like it is time to drop the oil pan and look at the rods and mains. The drop in oil pressure indicates a bad main bearing. Driving this way will really mess up the crank. $$$

A loud knock is obviously not good and certainly could be a bearing. However, on the 216, the oil pressure that you notice is relatively normal. It is freaky, but sitting at a light with a hot engine, the oil pressure can drop to next to nothing in a healthy engine. You do need to figure out that knock. Good luck,
Steve O

the way you tell it it is most likley going to cost to repair so I would look for a later 235 and install...doc

Low oil pressure on these motors is often caused by bad cam bearings. But your running oil pressure is not too far off from normal. I suspect your noise is a rod knocking. Some folks suggest using a stethescope to listen to the engine, or a piece of fuel hose, touched to the motor at or near each cylinder. Others say you can pull the spark plug wires one at a time until the noise softens. If you catch the problem early enough you may be able to pull the oil pan and adjust the offending rod. Do you have a shop manual?? If not, get one. If your rods have not been adjusted too many times before there will (should) be some shims on the rod cap bolts between the rod and cap. You can take out 1 or 2 shims from both sides and put it back together. Even the shop manual calls the rod bearings "selective fit". It's really a trial and error method to determine if the rod is tight enough. It should not bind on the crank or be sloppy. You should be able to snap the rod back and forth along the crank bearing journal with thumb and forefinger. Hopefully the crank has not been scoured too much. Good luck.