1974 EB, 302. Ran into an issue replacing my timing chain set. Replaced with a Melling 3358SA kit for a 74. Ran engine for 15-20 minutes then pulled pan to replace rear main seal which was leaking. (I had previously replaced but screwed it up). When I went to clean up pan to replace, I found fresh aluminum shavings in the pan. Well, unknown to me sometime mid 72 Ford went from a 1 piece fuel pump eccentric to a 2 piece and the cam timing sprocket changed with it. My engine had the original nylon toothed sprocket and a one piece eccentric. If you put that eccentri on a a 74 type cam sprocket, (which is what the year is of my truck and what I ordered), it sticks out too far and rubs on the inside of the timing cover carving it up in a circle. You can't hear it, and it did not affect its running except for putting aluminum into the engine. The only way I found it is because I screwed up putting in the rear seal the first time and had to take the pan off again.
I checked the code on the block, D2OE. 1972.
So, my question is, was the engine replaced at one time by a previous owner, or was this engine put in at the factory from stock the plant had?
You are misinterpreting the significance of the Ford Engineering number prefix. D2OE is not definitive without context. D2OE-6015-AB is the whole number. It signifies that the Part Number for the item was allocated from a PLM database and assigned to a drawing. The owner of the drawing would have put the number on the casting of the block for identification. When you decode it properly, it means that the part number was pulled with the intent to install the part into the 1972 year model Intermediate Car Engine group, with a root number of 6015, which is a block, in the first intended version, with one significant revision to the original drawing.
It is entirely possible for a part number to run for dozens of years without a significant revision, so the part number can be used for decades. Or, the part can be changed significantly in the next model year. Some parts can be functionally identical, but used concurrently. The C5AE-6015-E is a block for a 289 that was used at exactly the same time as the C6AE-6015-C they just came from different foundries. The B6AZ-11450-A starter relay ran from 1956 until well past the 1977 Bronco. At least 25 years. The C7AW-B rear axle housing is found in every 67-77 Bronco.
But if you have some context, you can divine some things about some parts. I happen to know that the D2OE-6015-AB was a fairly short-lived block part number. It was revised in 1974, and became the D4DE-6015-AA and D4DE-6015-BA. The D4DE block ran thru 1977. So the D2OE was only serviced in the 72 and 73 model year. But I only know it, because I study it...and I can certainly be wrong. I have a limited sample size, and I can only go by what I experience, and what I observe. And I've never heard of a D3xx small block ford. (not counting the 351W)
If your 74 Bronco has a D2OE block, then someone changed the engine.
The D2OE was not installed at the factory from "stock the plant had." The random use of old parts is a mythical tale that has been perpetuated by people with an incentive to lie. It's nonsense.
