I've been doing quite a lot of work to my car over the Winter and just now on the home stretch, getting closer and closer each day to getting it back down off the stands.... Throughout my ownership, I've had this most annoying "squeak" coming from (I thought) behind the dash someplace that would occur during low speed operation on uneven surfaces (stone driveway), and over bumps/expansion joints. So, while I was taking my cooling system apart, I came upon a aluminum-to-aluminum contact point that when bumped with my fist, sounded just like the the squeak coming from behind the dash... It happend to be between the filler panel at the front of the hood opening that the tabs on the back of the radiator slot into. What follows is a crappy cellphone photo description of what I'm talking about and how I saught to correct it. Jury is still out as to whether I've achieved success, but I'm fairly confident..
This photo shows the filler panel at the front of the hood opening. On the left of the panel, you can see the little slot that accepts a tab on the front, top side of the radiator:
This photo shows the tab on the front top portion of the radiator before I wiped it off. You can see that there is a little residue present from the aluminum-to-aluminum contact:
To correct this, I added a very thin strip of adhesive-backed foam rubber that I purchased from McMaster-Carr. I would recommend doing this step when getting to the point of installing your radiator if the 427 set-up is the same as it is on my 289 - I'm not sure why it wouldn't be from photos I've seen:
This pic shows the foam rubber in place:
One final photo showing the foam rubber sammich. No squeaks coming from this area again..:
My hypothesis is that with the ease of sound travel through solid objects, the squeak coming from this area made it's way through the frame and my subsequent perception was that the origin was somewhere behind the dash. I can tell you that I also had the dash out of the car over the Winter and there is nothing back there (save for downtubes to tunnel aluminum already mentioned) that would create the annoying-to-me squeak I was hearing.
Hope this helps you or someone else. I'll probably add this to my "ownership log" for #2124 once I confirm for sure the squeak is licked.
- Allen.