What year is my motor
 

I have a new question, based on looking under my hood with the Haynes manual in hand. In chapter 2 C-6, picture 7.8, in a sidebar to the picture it says earlier models have twelve bolts for the upper intake manifold, newer models only have six. My car only has six bolts for the upper intake manifold, so uhhh, what year did GM make this switch? Also, my motor has 3400 SFI stamped on the upper intake manifold. Any ideas to pinpoint what year this motor is?

Try looking on the drivers door for the manufacturers sticker.
-Smurf-

Not quite checkmate, because I know what is SUPPOSED to be there, but it isn't. If it was the same motor that came with the car, it would have twelve bolts for the upper intake manifold, but mine only has six, which GM started doing sometime after 1999, the year of the rest of the car. I was just wondering what year GM switched from twelve bolts on the upper intake manifold to six? Any ideas?

wat car did u get the engine from?

check the stamp on the upper left (i think) of the lower intake manifold.. should be an 00 or 03 or something.

99's definitely had 6 bolts. You can also check out the EGR port on the UIM that changed from 99 to 00.

Yes 99 was the switch to 6 bolts for the UIM.

The 99, 00, or 03 on the mani is the year of the mani, not neccessarly the engine itself

Ok, cool! Thanks for the assistance, gang. maybe it is the O.G. motor after all, because I know that on right side of the lower intake manifold, it is stamped 99. So much for the Haynes manual, ehh? Anyway, thanks for the help!

All 3400s have 6 bolts on the plenum..

The 1993-2000 3100 (VIN M, RPO L82) had 12 bolts