[dar83501]

I just bought an Olds Big Block to drop in my '87 Oldsmobile Cutlass Supreme (yes, it will fit...I'll MAKE it fit).

This engine is definitely an oldsmobile big block, but my research on figuring out what exactly it is has thusfar been pretty inconclusive. If anybody can help me out, I'll describe what I know about the engine, and what casting numbers I've found on it below.

This engine was rebuilt approximately 20~25k miles ago. I was *told* it came from a late 60's car, and is a 455. The engine has several contradictory things about it which confuse me as to what it actually is.

-Flywheel bolt pattern is a 6 bolt, and using calipers it appeared that two of the bolts were offset roughly 1/4" or 1/8".

-The engine had "B" stamped heads. The 455 didn't come with B heads, the 425 did. I do know they are interchangeable however, and it is very likely when the engine was rebuilt, that they placed 425 B heads on it if it is indeed a 455. I have heard they are nearly identical to C heads. The numbers on the heads and the numbers on the block do NOT match.

-There's an Edelbrock Performance 455 Olds intake manifold on this engine. This doesn't mean much, because the 425 and 455 are the same block.

-The following identification numbers have been found, and my understanding of them:

1.) On the back of the block, behind the flywheel, on the bellhousing, upper right hand section, is the following:

F 3
A

The F and A appear as they are, and the 3 is offset and tilted towards the F.

My understanding is that all oldsmobile 455 blocks were marked with "F".

I have no idea what the "A" and "3" signify.

2.) On the back of the block, below and to the right of the distributor, the following is marked:

5

241

CFD

My understanding is that the 241 is Julian Code for 241st day of the year, making the block's manufacture in August or September some time, but I have no idea what the "5" or "CFD" stand for. These numbers/letters appear as above.

3.) On the front of the block, centered directly above the water pump, is what I understand is the engine casting number. it reads:

389244D.

The "D" on the end is quite large.

According to my research:

the "3" stands for Oldsmobile Division of General Motors

the "8" stands for the last digit of the year the motor was produced, making this a 1968 motor.

the "D" stands for the production plant, which I believe in this case was a plant in Georgia.

I also understand that the last six digits correspond with a chunk of the original vehicle's VIN.



All my research on the casting number "389244D" has resulted in a supposed 425ci motor.

This doesn't make sense to me, because I thought the 425 engine was dropped in '67, and the number on the casting would make this engine a '68.

My theory behind this, is that the motor was produced towards the end of '67, to be placed in a '68 vehicle, making it a 455. When the engine was rebuilt, they decided to replace whatever heads were on it with B heads from a 425.

Any clarification or help would be greatly appreciated!

Edit: I forgot to mention, one possibility I have thought of is that this is actually a 425ci engine, with a 455 crank and flywheel. I have not removed the flywheel yet to check for markings on the crank.