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Tech Tips :: C3 Related Tech Tips :: Retrofitting 73-up rubber body mounts onto 68-72

Information
The
rubber body mounts found on 73-82 Corvettes vastly improved noise and ride
over the solid aluminum mounts used on the 68-72 models.

It is
possible to retrofit the later rubber mounts on 68-72 and reap the
benefits of a better ride, less road noise and less risk of fiberglass
stress cracks.

I recommend buying a body mount kit as it also comes
with all new bolts, washers, nuts and shims. These kits can be had for
about $150.

1. start by placing the rear of the car on jackstands
(rear wheels off the ground) and remove the spare tire carrier.

2.
You now have easy access to the rear bumper brackets. There 2 in the
center that go to the license plate area of the body, 2 that go to the
innermost bumper mounts, and 2 that go to the outer bumper mounts. The
rear section of the body is very strong and contrary to the front it does
not have to be supported during the lift.

3. Disconnect the antenna
grounding strap.

4. Disconnect battery cable where it mounts to the
frame.

5. Loosen parking brake adjustment as much as it will go.
The adjustment is in the transmission tunnel, before the cable splits off
to the wheels. You do not have to completely disconnect the
cable.

6. Now for the front. Start by removing the front grills.


7. Remove the one bolt holding the corner bumper bracket to the
frame extension. The frame extension is the large piece of flat steel that
goes from the front of the frame horns to the bumpers. There's one on
each side.

8. Remove 2 bolts on each side holding the frame
extension to the frame. Remove frame extensions.

9. IMPORTANT! The
next step will disconnect the whole front of the body from the frame. YOU
HAVE TO SUPPORT THE FRONT OF THE BODY AT THIS POINT. The weight of the
front is enough to collapse the body if you don't!!!

10. Place a
floor jack under the center of the front body transverse beam. This is the
steel piece just infront of the radiator.

11. Remove 4 bolts (2
each side) holding the body support to the frame. 2 of these bolts were
hidden by the frame extension bracket removed in step 8. The other 2 are
just rearward from the bolts removed in step 8.

12. Now it is time
for the bodymounts. There are a total of 8 mounts. They are referred to as
#1-#4 (left and right). #1 is behind the side gills, infront of the
firewall. 70-72 owners have it made as the gills remove for easy access.


13. #2 is behind the kickpanels. Remove the sillplates and then
the kickpanels. The bolt is now accessible.

14. #3 is behind the
door. Remove the rear wheels and then the access plate on the front of the
rear wheel well. The bolt is now accessible.

15. #4 is behind the
rear wheel and visible after the wheels have been removed.

16.
Remove 2 bolts to loosen the master cylinder. Tie the mastercylinder to
the alternator so that it clears. You do not have to disconnect the
brakelines.

17. Remove the bolts holding the steering column
rag-joint together. Don't forget the safety studs.

18. Remove
the rocker panels.

19. The body is now separated from the frame
9atleast as much as we need to lift it the required 4").

20.
Place 2 more floor jacks, one on each side, approximately 2/3 back under
the doors. Carefully test the rigidness of the birdcage rail by lifting
slowly. On mine I had problems with the rail bending, so I had to move the
jack back and forth until I found a rigid enough section.

21.
SLOWLY lift on all three jacks. As you lift, look in the engine
compartment, under the car, etc to make sure everything is moving
freely.

22. You will have to lift until you can just see the top of
the frame under the doors.

23. Now you can remove all the old
mounts. Note any shims that are found. Be aware that shims can stick to
the body. They have to be removed as the new mount won't fit with a
shim in the way.

24. Mount the new rubber mounts according to
instructions. They do not all go in the same way. If shims were used on
the old mounts, you can tape the shims to the new rubber mount. Use
masking tape. This, by the way, is how the factory did it for ease of
installation.

25. All mounts should slide through the holes in the
body. If they don't, you may have misaligned panels. On mine, all fit
except #3. I had to dremel the holes until the mounts installed properly.


26. Lower body down.

27. Re-attach the front end first,
using the highest possible attachment. This is done by lowering the front
until the bolt holes line up, install bolts (but do not tighten), lift
front as high as it will go and then tighten bolts.

28. re-install
all items removed in the earlier step, except the steering column
rag-joint.

29. The column will not line up as the body now sits
~3/8" higher than with the solid mounts. Loosen the column where it
attaches to the firewall, and also the upper bolts.

30. Push the
column down in the engine compartment until it lines up. tighten mounts
and re-install rag-joint bolts.

31. Enjoy the new ride!!!

 

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