Day after day, we get calls from people who have a Cad motor but are unable to tell what year/model they’re looking at. Since many Cadillac 472 and 500 engines use the same block, and the later (425 and 368) engines look similar, as well, you’ll have often to have a look deeper than the block casting numbers to finally determine which species of torque animal you have there. For a printable PDF engine ID guide, please visit the tech section of our web site.
Block ID:
The first step is to ID the engine block. The block casting number is found at the rear of the Cadillac engine, between the intake manifold and transmission bell housing, right next to the oil pressure sending unit. The casting number is the raised, cast in number on the passenger side. Note that the ’68-’69 (and a few rare ’70 472s) use a block that looks identical at first glance, but bears different casting numbers (ending in 6238), has smaller oil passages and does not have clearance for a 500 crank (rod bolt notches in bottom of cylinder bores). Fine for a mild street engine, but unacceptable for a serious performance engine.
Piston ID:
Crank ID:
Cylinder Head ID:
From ’68-’73, the heads were of the 76cc small chamber design. These heads have one of 3 casting numbers. All ’68/’69 and ’71-’73 cars were equipped with a smog pump from the factory, while the ’70 cars were not. The ‘250 and ‘902 heads are equipped with built in smog rails, while the ‘950 heads were not. Not all ‘250 and ‘902 heads were drilled for smog rails, if they were installed on a non-smog ’70 car, even though the extra material is in the casting.
The 120cc ‘large chamber’ cylinder heads were introduced on the ’74 472/500’s and continued through 1976. These heads have one of 2 casting numbers (‘493 with smog rails cast in and ‘552 without).
The 96cc 425 heads are very similar to the large chamber 472/500 heads, and even use the same valves, springs, etc. Many people claim that it is a good idea to use these heads on a ’74-’76 472/500 short block, as it will raise your compression to 10:1. While this is technically accurate, it is not actually a good idea for several reasons.
The aluminum heads we have available at this time for the 472/500 engines, and have a modern, closed chamber design, with 72-80cc chambers, and have raised ports with oversized valves.
For those of you considering power above all else, head flow is extremely important. Other head choice considerations include compression ratio choice. There is a high compression piston (10:1), we have in production at this time, for the 120cc heads. As for flow, the 76cc and 120cc heads flow within a few percent (all 5 castings) with stock valves and no port work. The ‘423 heads flow significantly less. When ported and equipped with oversized valves, 76 & 120cc heads perform well. Our un-ported aluminum heads outflow ported iron heads.. The aluminum heads also have much more room for porting than the best iron heads, so they can be ported to flow much better. The power limit on the ported iron heads is well beyond what most bracket engines are built to make.
Other engine ID notes:
’68 – mid ’70 engines used the first generation heat operated choke, with an exhaust passage around the front of the carb. These intakes have a cast rectangular box-shaped choke well. Mid’70-’73 engines do not have the heat passage around the carb, and have a round choke well with what looks like a freeze plug in the bottom of it. Many ’68-’70 engines also had no EGR valve. All OEM 472/500 carbureted intakes are dual plane. Note that while electric chokes and HEI distributors were ’74-up only from the factory, it is not un-common to find them retrofitted to early engines.
Most parts outside of the block, crank, pistons, and head castings are interchangeable between the ’74-’76 472/500 and the ’77-’79 425 engines. Some parts require other parts be changed at the same time for compatibility.
Finding a 500 can be difficult due to the lack of external identification. While all ’70-’76 Eldorados and all ’75-’76 cars (except the Seville) came from the factory with a 500, it is generally very difficult to tell if the engine is original on a 30+ year old vehicle. As for the difference between a 472 and 500, there is very little. In most cases, if they are the same year, they will be absolutely identical except for the crankshaft and pistons. For instance, there is no ‘472 head’ and ‘500 head’. The head style is determined by the year, not the crank. The pistons must match the crank/head combination, or you can run into all sorts of trouble.
Year | CID/L | VIN | Description | Block # | Bore | CR | Head # | Chamber | Crank # | Stroke |
---|---|---|---|---|---|---|---|---|---|---|
68-69 | 472/7.7 | Early / High Compression | 1486238 | 4.300 | 10.25:1 | 1486250 | 76 | 1486424 | 4.060 | |
70 | 472/7.7 | R | Early / High Compression | 1485200 | 4.300 | 10.0:1 | 1486250 1497902 1495950 |
76 | 1486424 | 4.060 |
70 | 500/8.2 | S | Early / High Compression | 1485200 | 4.300 | 10.0:1 | 1486250 1497902 1495950 |
76 | 1496793 1495094 |
4.304 |
71-73 | 472 / 7.7 | R | Early / Low Compression | 1485200 | 4.300 | 8.8:1 8.5:1? |
1497902 | 76 | 1486424 | 4.060 |
71-73 | 500 / 8.2 | S | Early / Low Compression | 1485200 | 4.300 | 8.5:1 | 1497902 | 76 | 1496793 1495094 |
4.304 |
74 | 472 / 7.7 | R | Late / Low Compression | 1485200 | 4.300 | 8.25:1 | 6024493 6024552 |
120 | 1486424 | 4.060 |
74-76 | 500 / 8.2 | S | Late / Low Compression Carbureted or FI (Analog Port) |
1485200 1486200 |
4.300 | 8.25:1 | 6024493 6024552 |
120 | 1496793 1495094 |
4.304 |
77-79 | 425 / 7.0 | S/T | S: Carbureted T: FI (Analog Port) |
1609110 | 4.080 | 8.2:1 | 1609112 1609423 |
96 | 1609142R | 4.060 |
80-85 | 368 / 6.0 | 6/9 | 6:Carbureted 9: DFI (TBI) |
C:1615255 F:1620734 |
3.800 | 8.2:1 | C:1615188 | 1609142 | 4.060 |
Cad Company