I am looking at a 78 CDV with a 425. The person who owns it states that he bought it several years ago, drove it minimally, and one time when he started it, there was a fairly heavy knock. Yesterday, I went to look at the car. It has been sitting in its current position for 3-4 years, and has not been run. Since heavy knock to me sounded like a bearing, I said, what harm would it be to try to get it running? Well, we put in a battery, I cranked it until the oil light went out, and it started after about two tries, stalled a few times, but finally began running smooth. There is a definate knock. It sounded like it COULD be a rod, but it wasnt THAT bad. I dont know how to tell. from the top of the engine, it sounds like the top of the engine. From the bottom, it sounds like the bottom. As the car warmed up, the owner was amazed becuase the knock had all but gone away at idle, and as you sped up the engine, it did get worse, but I think I'd drive it and just wait and see. My question is whether or not there is some way to tell, and could a bent push rod or a lifter thats not getting oiled cause a louder knock that might sound like something worse than it is. The car has only 59K miles on it.

One trick is to remove the spark plug wires one at a time and see if the knock changes. This would indicate a crapped rod bearing.

There is a chance it may just may be carbon in one of the cylinders. At that low mileage a bad rod is unlikely unless the engine was really abused.

Try some of the tips offered by others for carbon blasting. Tranny oil down the carb, or even water has been known to work.

Good luck.

Ok, So I did go over and do the thing with the spark plug wires. The knock never changes, the engine just misses on the appropriate cylinder. So I guess thats a good bet that its something up top, which of course is a good thing. The knock is getting less and less. Now there is a transmission issue, and I'll post that in a new thread becuase I fear that it will go unnoticed in this one. Thanks for your help. I will try next to clean the engine using some of the methods mentioned.