I am putting a buick v6 3.8 into a model a frame (stock C channel, boxed). I am using stock motor mounts. ( not same as SBC and not same on both sides ) with a fabricated (from 1/1/2 x 2/1/2 rect) cross member to connect to frame. I would like to have the xmember as bolt-in rather than weld in. Two options I am looking at are : 1. an open side up piece of C channel welded to inside of frame rail. Xmember would sit in this and have a vertical bolt holding it in. From a welding point of view the C piece would be welded directly to frame (along bottom, up sides) plus horizonal gussets from side to frame or welded (along bottom, up sides) to a separate plate having a triangular shape.(plus gussets again) This plate then welded to frame along top side and along diagonal sides. This latter option considered as I have read to avoid vertical welds on the rails, or at least C rail, but boxed ? 2. use a rectangular plate with a smaller rectangular hole in it into which the xmember is welded. This plate would would then be bolted by 4 bolts going through the frame rail. Would consider using step bolts or anti crush tubes although the area actually is double walled with inner rectangular piece as frame has a front clip (mII) installed. hopefully this drawing shows what I mean. http://web.ncf.ca/da229/pics/motorxmem.jpg Comments or suggestions? Thanks
With a boxed frame, you really don't need a crossmember for the engine, if there's a stout suspension crossmember in front of the engine. Just weld brackets to the frame on each side that are long enough to reach the motor mounts. With an open channel frame, you'd want a full crossmember under the engine, because the weight of the engine would twist the channel if you just stubbed out from the frame for the mounts. Now, for your ideas that you presented: If you put thru bolts thru the frame, you'd be better off with a tube insert welded into the frame for each bolt. So building a "shelf" (your C channel) to lay the crossmember on at each end might be less work.
I got the idea of the crossmember from seeing one for the engine available from Speedway and CE for that engine. Neither seemed right for my motor placement. Now having fabed mine I realize that if I cut away the centre part , then what is left would serve as the side brackets, if welded to the rails. I want to stick to having the crossmember bolt-in as I think putting engine in/out by unbolting it will be easier than trying to do bolts through the mounts on motor. What is advantage of welded bolt tubes over unwelded or step bolt?
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