[srelaz]

Hello, I am new to Pontiac and wanted to know more about the motor mount hole locations on the blocks.

Wikipedia is saying that the Pontiac V8 came about in 1955 and lasted through 1981. Do all the Pontiac blocks use the same three motor mount bolt hole locations on the sides of the block for all those blocks produced from 55 - 81?

I would appreciate your help!

[GTO Noob]

Well PY sells motor mounts that 64 - 74 exc 455's and conversion brackets for motors 76 -79 to fit into older cars so I would say that there probably is a difference. I'm sure somebody more experienced than me can comment on this

[Will]

1969 and older share a two-bolt arrangement, so there will only be two bolt holes in the '69 and older blocks.

In 1970 the Firebirds began using a new 3-bolt mount while some models still used the older style 2-bolt mount plus the new blocks had to be able to be used as service replacements for older cars, so all '70 blocks have 5 bolt holes in them and can be used with either mount.

This arrangement continued until mid-year '77 when the old 2-bolt mount holes were eliminated. However, I've seen numerous pictures of '77 - '79 blocks that still have the bosses cast into them for the holes, the holes just weren't drilled so it would still be possible to drill and tap the holes for the older mounts in a '77+ block.

'78 was actually the last year that Pontiac manufactured a traditional Pontiac V8 - the 400. The 400s used in the '79 TAs were holdovers from the previous year's production.

The 301 and 265 V8s which were produced into '81 were a different design and share only distributors and timing covers with the earlier engines. I doubt they have bosses for the older style motor mounts in the blocks, and who'd want to install one in an old car even if they did?

[Shadowjack]

Once you get back before 1965, the differences start adding up. Don't know the details, but the mounts are not the same for the very early engines, plus a lot of other things were changed incrementally every couple of years.