i have an olds short block the casting is 396021ff8 the pistons read l2323 .040 i think that is the overbore but im not sure. the motor is an old mondello piece if any one could help i can provide some more helpful numbers. thanx

 

That casting number is for a 1972 - 1976 455.
Not sure about the pistons but I would guess they are 0.040" over.

 

If my memory is correct, that piston part # is a TRW (Speed Pro) forging, flat top, .040" oversize. Good slugs. Ha-that's a good one considering you have just about 357 cu. in. now. Get it- 357 slugs!

 

having the same problem found an old book on cars but trying to verify which i got 425 2 bld or 400 the only this is a oldsmobile 66 cutless w on the bock and m on vin # m is for 425 4 bbl that not what is under the hood

 

400 nor 425 were avaiable in the 66 Cutlass. Only 400 was available in the 66 442. Check Olds FAQ on line for the info on the 66.

 

IRIS,
Yogi442 is correct. In 1966 thr Cutlass and F85 got the 330CID V8, the 442 got the 400CID V8 and the big cars got the 425CID V8.

Olds did not indicate the engine option in the VIN number. The engine code was stamped on the engine on the front of the right cylinder head.

It is possible that the engine is not the original engine and if what you ment by VIN is the engine code on the engine keep in mind that you will need the engine casting number and the engine code as Olds used the same codes from year to year.