[Oldsguy]

the 455 can be recognized easily by a couple of things. The easiest is the oil fill tube which is located on the top/passenger side of the engine casting directly above the timing gear cover. The tube is about 8 inches long and has a cap on it which turns a quarter turn to lock similar to the old style fuel caps. Another way is the water neck by pass which is located on the front of the thermostat housing, on early models it was a short straight tube only an inch or less long, on later models it was curved, at any rate a short section of rubber hose was clamped between it and the water pump, this allowed a certain amount of water to circulate through the block even before the thermostat opened. Most all if not all Olds V8s had this. These are only two ways to tell an Olds Big Block from other GMs, but the Olds Small Blocks also had those two features, to tell a BBO from an SBO look at the heads. On the driver's side head on the lower left corner (as you look over the fender at it) you should see a letter cast into it. This indicates a big block 455, 425, 403 or (I think) 400. If there is a number or a number with a superscript letter then it is a small block. Also, the 455 measured about eleven inches from the top front of one head to the top front of the other head (width of the intake manifold basically) The small block was about nine inches. The best way is to get the engine code from the top of the engine block located on the flat shelf opposite the oil fill tube as you look at the front of the engine. If you get this number I will try to decode it for you, this will tell you everything you need to know about the engine. Good luck.