[Alvin]

On 1973 and 1977 A-body Pontiac LeMans, etc.; are the 400 Pontiac engine motor mounts, stands, etc. the same?

[camerjeff]

Sorry but no, 64-74 A-bodies use the same type,

https://secure.amesperf.com/qilan/Search_Web

75-77 use What I always called the "Captured " Style.

http://www.autopartswarehouse.com/de...QWSEM2292.html

[Brian Baker]

What Jeff said. By '77 they used the "triangulated" style mount that was used on the F-body since '70, where the 3 bolts holding it to the block were in a "triangle" and the frame side of the mount was a "clamshell".

[Alvin]

Thanks for the replies and info.

I found this concise Pontiac engine block motor mount information from Wild About Cars Online and wanted to share it.
Join for access to the full library here: http://www.wildaboutcarsonline.com

1970 Block (s)howing all five potential motor mount holes (above). Red indicates 1964 up and A-Body mounting holes. Green arrow shows hole added to allow fitment in Firebird. Blue arrows show holes eliminated in later blocks.

This complete Pontiac engine code ID article can be here:
http://wildaboutcarsonline.com/cgi-b...=9990390327777

[Alvin]

Originally Posted by Alvin

Thanks for the replies and info.

I found this concise Pontiac engine block motor mount information from Wild About Cars Online and wanted to share it.
Join for access to the full library here: http://www.wildaboutcarsonline.com



This complete Pontiac engine code ID article can be here:
http://wildaboutcarsonline.com/cgi-b...=9990390327777

Originally Posted by Half-Inch Stud

Me thinks a Green Arrow is needed for that Upper-Middle hole.

Me not aware of the Rear-most Hole Ever going away (1964-1983 301, but maybe it did on the 265)

So I ask is the Text really correct?

Modify & Correct as you feel is valid. Feel free to comment at the website: http://wildaboutcarsonline.com/cgi-b...=9990390327777

Motor Mounts

1955-58 blocks did not use side-mounted motor mounts, but were mounted from the front of the block and at the rear. Starting in 1959 side motor mounts were used with two holes. as was the common practice in GM. In 1970, all blocks had 5 motor mount holes on each side, but they were not always tapped. The additional holes were to allow installation in the new Firebird/Trans Am frame. The 1977 to 1979 V8s did not have the rearward motor mount holes at all, making it very difficult to install the late blocks in a 1964-77 Big Car or a GTO and Tempest.

[johnta1]

The 3 holes that aren't pointed to by the red arrows, are the ones that were added for the 70 Firebirds.

The later years block that only had 3 holes used the ones not pointed to by the red arrows.
(basically the older 2 bolt mount holes went away)

[Brian Baker]

Text is incorrect pertaining to blue and green arrows.

[Alvin]

Originally Posted by Brian Baker

Text is incorrect pertaining to blue and green arrows.

K. What IS the correct text for blue and green arrows? Thxs

[Brian Baker]

Originally Posted by Alvin

Thanks for the replies and info.

I found this concise Pontiac engine block motor mount information from Wild About Cars Online and wanted to share it.
Join for access to the full library here: http://www.wildaboutcarsonline.com



This complete Pontiac engine code ID article can be here:
http://wildaboutcarsonline.com/cgi-b...=9990390327777

Forget about the blue arrows completely. The red arrows are for the pre-'70 A & B body (and G?) and post-'70 up to about 1975. The 3 mount holes that form a triangle (that have no paint removed from around them like the red arrow holes do) are for '70 and up F-body, which eventually became the mounting holes for the entire Pontiac lineup by 1977. Some speculate the mounting hole height on the later 3-bolt hole only blocks (in respect to the oil pan rail) is different from these 5-bolt hole blocks, but I have not seen physical proof of it.

[Alvin]

Originally Posted by johnta1

The 3 holes that aren't pointed to by the red arrows, are the ones that were added for the 70 Firebirds.

The later years block that only had 3 holes used the ones not pointed to by the red arrows.
(basically the older 2 bolt mount holes went away)

Thanks for the reply John.

Originally Posted by Brian Baker

"…The 3 mount holes that form a triangle (that have no paint removed from around them like the red arrow holes do) are for '70 and up F-body, which eventually became the mounting holes for the entire Pontiac lineup by 1977..." (original image below)

Props for your clarification Brian.

To be clear: You are referring to the 3 holes circled in beige in the revised photo (below), yes? Thanks.

[Brian Baker]

That's right...the 3-holes with the "squares" around them are for the '70-up F-body. I don't know when the change-over started from the 2-bolt mounts on non-F bodies to the 3-bolt arrangement, but the consensus is 1975, and by 1977 all blocks had only 3-holes regardless of what body they were going in (my Can Am for instance has a 3-bolt mount block and shares the same type mount as the F-body).

[Alvin]

Originally Posted by Brian Baker

That's right...the 3-holes with the "squares" around them are for the '70-up F-body. I don't know when the change-over started from the 2-bolt mounts on non-F bodies to the 3-bolt arrangement, but the consensus is 1975, and by 1977 all blocks had only 3-holes regardless of what body they were going in (my Can Am for instance has a 3-bolt mount block and shares the same type mount as the F-body).

Thanks for the heads up!

[johnta1]

In 1975 all the mounts became 'clamshell' type, which used the 3 bolt mounting.

[Brian Baker]

Originally Posted by johnta1

In 1975 all the mounts became 'clamshell' type, which used the 3 bolt mounting.

Point I was trying to make was pertaining to the block casting. I know the 3-bolt clamshell mount started showing up in models other than the F-body in '75, but the '75 blocks were still cast with 5 holes. The '75 455 I had in the Discomobile had 5-holes. By '77 the 5-holes were gone, the original block in my Can Am only has 3 holes.

I imagine Pontiac did this for instances where service replacement blocks would still fit in earlier models with the 2-bolt mount...but might be interesting to find if there were any non-F body cars produced in '75 still using the old 2-bolt mount...never say never.

[johnta1]

By '77 the 5-holes were gone, the original block in my Can Am only has 3 holes.

I have some 77 TA engines that still have the 5 holes.
Probably the big car engines went to 3 hole.

I think when Pontiac started to drop the 400 production all the engines went to 3 holes.

[Brian Baker]

Originally Posted by johnta1

I have some 77 TA engines that still have the 5 holes.
Probably the big car engines went to 3 hole.

I think when Pontiac started to drop the 400 production all the engines went to 3 holes.

See? Never say never.

Did you mean when they dropped the 455 production?