Engine question; how can I tell for sure if my engine is a W31 or a plain 350? It has the 4 bbl Q-jet and cast iron intake, but that could have been an easy swap. The heads have the "5" casting. I've read that there were only two Olds 350s in '69; a 2 bbl with 9.0:1 compression and a 4 bbl with 10.25:1 compression. I suspect my Cutlass's engine originally had a 2 bbl. I can't remember the seriel # above the timing cover, but I recall it having three consecutive 5s in it.
Any comments/advice?

- GoldOlds

 

The only way to tell for sure is to find a numbers-matching block installed in a documented W-31 car. The W-31 (expecially in 69) used the same castings for the block, heads, crank, and intake as any other 350. Except for the larger than normal harmonic balancer, the differences are all internal. Larger valves, 308 degree cam, and flattop 10.5:1 pistons (your book is wrong about available 69 motors, by the way). The carb and distributor numbers are different for the W-31 also. All of this stuff is bolt-on, so there's still no way to prove it was a factory-built W-31 (though if it has all the parts, it should run the same).

There is an easy way to prove it's NOT a W-31, however. Check the VIN derivative located on the front driver's side of the block. It should be a nine character stamped number. The first character is always a 3 for Oldsmobile division. The second character is the year and will be a 9 for a 1969 motor. The third character is a letter designating the build plant. All W-31 motors were built in Lansing, which would be designated by the letter M. If this third character is anything other than an M, the motor CAN'T be a W-31. Of course, Olds made lots of non-W motors in Lansing, so the fact that it IS an M doesn't prove anything, but a non-M can disprove it.

 

Thanks, Joe, much appreciated. Where can I find a list of the available hp/tq ratings and codes for all the different Olds 350s in '69? I'd like to know what sort of performance this engine started off with. It doesn't look or sound very heavily modified - cast iron intake, plain ol' Q-jet, no headers etc. With the exception of the Taylor wires and Edelbrock breather and valve covers, it looks bone stock.

- GoldOlds