|Here is some interesting information about one of the more mysterious motors in our ID tables. There's been no doubt that this is a Pontiac mill. It appears in the 1975 Buick Shop Manual and has its own chapter for service. The rear axle table shows the intended usage was in the LeSabre and the Estate Wagon models.
It is entirely reasonable to see the Pontiac 400 being proposed as a California-only alternative to the 455. Who knows why the Electra 225 and the Riviera would have continued on with just the 455 for that state?
There are serious doubts that such cars were ever built however. There is no mention of a 400 engine in the sales brochure for 75. A Buick parts list from 83 shows no such engine used in 75. This parts list does show California and 49-state applications including 455s for California. There is even a Buick service bulletin regarding tune ups issued in September, 1975 that shows no such engine. The engine table attached to that bulletin shows every other combination under the sun that Buick supplied that year. No 1975 400s have turned up in messages on this site as far as I can remember.
Maybe some Buick engineers tweaked up the 455 to get it to pass California emissions after the shop manual was sent to the printers? Then the plan to install the Poncho motors was scrapped?
To my knowledge there is no data at all on a 76 application for this engine in a Buick. If anyone could guide us to some more resources for further information, it would be most appreciated. (You can post them on the web board.)
There are a few other non-Buick design engines (like the Chevy in-line sixes) that were used in the earlier years. These are not listed as such in the ID tables, mainly due to oversight. But maybe Bob C. can make the needed changes to show them as 'foreign' sourced motors.