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1941 firewall to frame mount

Started by falcongto@hotmail.com, March 16, 2021, 08:34:38 PM

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falcongto@hotmail.com

Question for all the resto gurus out there.  I'm redoing my 41 61 series and noticed something odd with the body mounts.  The body mounts all have rubber pads except for the bracket that connects the firewall down to the frame at the back of the engine bay (see attached Fisher body manual pic shared from other board member).  I've not separated them yet but it appears to be metal on metal with not even a thin rubber pad.  Why would GM isolate the body from the frame everywhere else but here?  I'm needing to know because I'm reconstructing my lower frame mounts under the A pillar and have to plan for the pad thickness with the new fab work.  That led me to notice this odd mount just in front.  Any thoughts as to what GM was thinking with this?

The Tassie Devil(le)

I would hazard a guess that the engineers wanted the body physically bolted tight to the Chassis in at least one plane, then the rubber mounts allow the rest of the body/chassis to flex.

At the Firewall, that is the best place to hold the body tight and in alignment, as the front that moves forward can flex at the extremity, as does the back, and the hood to Firewall/Cowl alignment remains perfect.

My '37 Chev Coupe was fixed the same way.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Brad Ipsen CLC #737

You have observed correctly.  On the 60S the front two mounts are bolted with only an anti-squeak pad and no rubber.  The bolt torque on all but the front mount is also very low with normal torque spec on the front bolt.  Also special light lock washers are used on all mounts except the ones on the front.  The torque was so light that a normal lock washer would not be effective.  On the convertibles this is all changed.  All mounts have no rubber but only anti-squeak pads and bolts have normal torque.  Also lots of shims to get correct alignment of everything.
Brad Ipsen
1940 Cadillac 60S
1938 Cadillac 9039
1940 Cadillac 6267
1940 LaSalle 5227
1949 Cadillac 6237X
1940 Cadillac 60S Limo