Body to Frame Bolts

I have a question,


Why on a 1955 Chevy do they used 3/8-16 hex Bolts to hold the body on the frame ? When the Rubbers and sleeves are like 3/4" ID .


Thanks Sid

So you can move the body on the frame that small amount and still have the bolts go through the holes. Also this allows some of the mounts to be off in location.

Get the body as square as you can on the frame before you bolt it down, and watch the bolt torque, so you don't crush the rubber mounts.

Hard to crush it to far with stock units. There is a tube washer assembly with OEM stuff. Even the Poly kits have a tube and washer setup that limits the compression.

Still, the recommended torque is a bit less than what you'd expect for the bolt size. There is some compression of the rubber.

I don't recall the torque my instructions had, but it sure compressed the rubber a lot! Probably all bottomed out on the spacer insert (I think it had them?). I do remember that the difference in ride and handling was great. One of the improvements that ranks up there with a stiff front sway bar.

My recollection is that the torque is 25 foot pounds, where a standard bolt that size would call for 30-35 foot pounds.

The rubber is compressed some, but tightening it past the point where the washer is bottomed out on the sleeve doesn't compress it anymore. I think the reason they don't go to 35 ft-lb is that the bolt head and/or lockwasher would dent the washer too much. I've seen washers that had big dents in them. 25 ft-lb probably prevents that from happening, but still crushes the rubber completely.