If you recall THIS TOPIC (http://www.chevelles.com/cgi-bin/forum/ultimatebb.cgi/topic/7/8877.html?) where I asked for opinions on crossmember mounts after boxing a coupe frame, I finally went ahead and finished/solved the problem.

I didn't have an extra crossmember, so I took one my brother had for a 70 impala with a TH350 which was about 5" too wide. I chopped the flat ends off, applied heat, and flattened the ends in a vice.

I had a 305/700R-4 laying around that would work perfect for mocking up the mounts for a LT1/4L60-E

After a little eyeballing and measuring under my chevelle, I positioned the crossmember where I thought it should go, and welded on these simple-yet-effective brackets. I welded them solid to keep dirt from collecting in the crack and causing rust later on.

http://www.chevelles.com/showroom/crossmember%20bracket.JPG

Sandblast, prime, and paint...

http://www.chevelles.com/showroom/painted%20frame.JPG

Next step is to start on the front suspension :cool:

Looks great! I'm getting ready to do the same exact thing to my 66. Boxing in the frame and all. Hope you don't mind if I copy your crossmember idea. Definitely looks like the way to go. Any other advice you would give to someone about to do the same thing. When you say you're going to re-do all of the factory welds are you just going to weld over the top of the welds or grind then weld? Thanks.

First I ground off any high spots and big globs, and sandblasted the welds clean, then I welded over the top of them. The factory welds have a lot of gas-holes, which can appear through your welds. I didn't worry too much about that, because I knew they were way better than what WAS on there, and it's just a frame so it doesn't need to look real pretty.

I used 1/8" steel to box it, and 1/4" x 1-1/2" for the mounts.

I'll drill out the holes in the mounts when I'm ready to bolt it together. I made the mounts longer than needed so that if I decide to put a 6-speed in it later, I can just drill new holes. I'm not sure if they're long enough for that, but they'll work for now anyway.

Here's another topic showing what I've done on this frame.
http://www.chevelles.com/cgi-bin/forum/ultimatebb.cgi/topic/2/27417.html?

Looks good Derek! With my HTH truckarm kit, they're solution is a metal 'tab' with holes in it, that you bolt into the stock holes, then weld it into the 'boxing', and you have a tab sticking out very similar to what you have done.

I still think you should consider an X-brace in the middle of the frame, that will greatly increase stiffness...part of it could also double as a driveshaft loop.
Another area I've noticed considerable flex on an A-body frame is right near where the firewall of the body would be, behind the front X-member. If I was doing a frame-off I'd figure out some way to control that as well.

I just did basically the same thing to the frame on my '67. I boxed the frame with 1/8th inch steel and used 1/8th inch L-shaped steel gusseted on the ends welded to the boxing for x-member mount. I drilled all the stock holes in them so I can put any tranny config in the car. I'll be modifying the x-member the same way.
-Scott

The X-brace is a good idea, but running the exhaust under it could be a PITA. I've got it this far, I think it'll be plenty for my mild car. I don't think I'll drive it agressive enough to need anything more than a boxed frame.

Thanks for the ideas though! :cool:

Originally posted by scooter67:
I drilled all the stock holes in them so I can put any tranny config in the car. Scott, I thought about doing that too, but decided the only way I'll change from my 4L60E to anything else, would be if I got a 6-speed for cheap, and I'm sure stock locations of holes wouldn't work anyway smile.gif

The reason I did it was because I'll be using a 200r4 tranny, and you can bolt it up to the th400 holes. I figured if I changed my mind it would give me the most options. I'm too lazy to shift manually anyway.:smile:
Scott