Author Topic: Where's the date code on a 403 Oldsmobile? (Read 4420 times)

Maxthe222 · « **on:** December 30, 2021, 08:05:01 PM »

Hey gang,

How do I actually determine the date code a 403 Oldsmobile block was cast? If the VIN has been re-stamped or has faded away, how can I tell? There is a clock on the back of the block, there's random numbers on the heads besides 4A, but what on the intake is the date code here? The number 279? Isn't that just the day of the year the intake was cast? How do I know if it was a '77, '78 or '79? This does have the vertical 77-78 water intake, but that could have been changed at some point.

olds403 · « **Reply #1 on:** December 30, 2021, 08:52:36 PM »

There are two 403 blocks 403 and 403X. On the block by the dizzy hole is the block 3 digit date code.’
The vin is on the drivers front under the cylinder head. You can not figure out if the block is a 77 78 or 79.
At 45 years old - finding a good block is hard enough. The cylinder heads are date coded and if still on the block you can figure out the year. Hope that helps

langss · « **Reply #2 on:** December 30, 2021, 10:04:39 PM »

Quote from: olds403 on December 30, 2021, 08:52:36 PM

There are two 403 blocks 403 and 403X. On the block by the dizzy hole is the block 3 digit date code.’
The vin is on the drivers front under the cylinder head. You can not figure out if the block is a 77 78 or 79.
At 45 years old - finding a good block is hard enough. The cylinder heads are date coded and if still on the block you can figure out the year. Hope that helps

Just for the sake of curiosity, what does a running 403 go for.