Sorry, I may be wrong but there are easy ways to tell. If the valve covers have 5 raised ribs running front to rear and 6 bolts, if the intake manifold has a gap underneth with a tin cover over the lifter valley like a Pontiac, if the oil fill tube is bent to the right side it is a 394. If the valve covers do not have any ribs and have 10 bolts, if the intake forms the cover over the lifter valley, if the oil filler tube is straight up and down it is a 425.
The VIN on oldsmobiles prior to 1971 did not indicate the engine installed. The engine code for a 1964 394CID 345HP Starfire/Jetstar I is JS. It should be stamped on the left cylinder head over the center exhaust port (if the engine has been apart it may be on the right head). The engine code for the 1965 and 1966 425CID 370/375HP Starfire/Jetstar I is NS. It will be stamped on the front of the right cylinder head. You may also want to check the engine casting numbers The 394 Block number is on the right rear of the block and will be 585786, The 425 block number will be on the flat spot behind the water pump to the left of the oul fill tube - it should be 381917 or 386525 with a casting code A.
There are a couple of other things that may have happened. Some states titled cars in the year they where sold or manufactured not the model year - So you may have an early 65 - or - someone may have changed the engine at some point.
By the way you may want to get the service manual for the car. It will give you the correct specifics for the car. The web sight you selected is wrong. It does not even have the correct data for my 1966. It lists the 360HP engine that was only available in 1965 and did not list the 375HP engine. It also shows the 345HP 400CID engine for the 1964 442. Everyone knows that the 442 had a 310HP 330CID engine in 1964 and the 400CID did not come out until 1965.
Send me your email address and I will send you some photos of a 425.
jdorour@bellsouth.net
John
[ November 01, 2005: Message edited by: jdorour ]</p>