Thread: th350 to th400 swap

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i am putting a 454 and th400 into a 78 camaro that had a 350 th350 setup. the trans mount is about 5 inches too short. any suggestions how to make this work? i cant find a new crossmember for this app and i dont have the equipment to fab my own

With no equipment other than a hacksaw and a welding shop somewhere in town, here's how I'd proceed.
Mock up the trans at the proper angle (0 degrees down bubble on the carburetor pad on the intake manifold). Use wooden blocks under the end of the tailshaft, leaving room to bolt the crossmember to the trans mount. Hacksaw the stock crossmember into 3 pieces, cutting it so as to leave an inch or two beyond the trans mount on either side. Make sure there are no other components on the car that will be in the way of the spacer plates you are about to make. Bolt the short piece onto the trans mount. Bolt the two side pieces to the body. Using a 3" wide strip of cardboard, cut two pieces of cardboard to the correct length to connect the 3 pieces of the crossmember together. Mark the outline of the outside pieces and the center piece of the crossmember on the cardboard spacers. Take all three pieces of crossmember and the two pieces of cardboard spacers to the welding shop. Have the operator cut or grind off the edges of the center piece or the outside pieces of the crossmember by about 3/16ths of an inch so that the spacer plates will be parallel with the centerline of the car and will look good. Have him fabricate two spacers made of 3/16ths thickness steel plate, 3 inches wide to match your cardboard spacers and tack weld the whole mess together. NOTICE I SAID TACK WELD. Take the new one-piece crossmember home and try it for fit. Any adjustments can be made pretty easily by grinding off the tack welds and re-positioning the pieces at the shop. Keep doing it until it fits properly. Then have the welder finish welding it , moving from one place to another on the crossmember so as not to warp the piece with too much heat in one area all at once.

Tech, good direction for the Garage Hobbiest. I followed your directions and it was understandable and if followed, Is a good piece to make the geometry work for app. I like it when all those who ask, get a direction to head into for their problem.

would i be able to just weld an extention from the center of the crossmember?

Originally Posted by seansz28

would i be able to just weld an extention from the center of the crossmember?

That's basically what I've outlined for you, but yes you can if there is nothing in the way. I've edited my answer to reflect "0" degrees on the carburetor pad.

i was looking at it today and it looks like i could just drill new crossmember mount holes a few inches down the rails. can i do this?

yes, you can.