I have a 47 Oldsmobile sedan with an 81 Pontiac Grand Prix subframe in it. My question is why does the subframe point UP in the front? When it was installed the car was leveled, the crossmember angle was set, and legs were even welded to the subframe to maintain that angle. The front frame horns just point way up and b4 I trim any of the inner fender panels I wanna make sure its not something stupid that we did. I never took geometry and Im kicking myself now for it! Kustomd has a 47 Pontiac that was done the same way and it drives and tracks just fine, I just dont like the the idea of how much fab work its gonna take to fit everything in the engine compartment.
Define "point way up". Pictures would help a bunch here. What was set level before it was welded on and is that area still level? If I remember correctly, those early 80s GM frames are about 2" higher (as measured at the top of the frame) at the radiator support then they are at the upper control arm mounts. The most important thing is being able to adjust the suspension to get proper wheel allignment and quality welded connections, anything else can be adjusted for in front metal placement. Gene
I had an "instruction manual" of sorts that I went by to do this. It was actually a series of magazine articles on this exact same swap. I set the angle on the subframe at the front crossmember (thats how they did it in the article). We took measurements from the front frame horns to the ground and from a point behind the contol arms to the ground. We actually welded "legs" onto it to keep it in place. We had prepped the Olds, gotten our wheelbase measurements, welded in a frame brace, and removed the old front end. This is where some dispute came in. In the article, they removed the rear wheels on the car and set it down until the front part of the frame (or what was left of it sticking out from the firewall) was level. The cross brace was welded across the top of the frame and checked level side to side also. I had people tell me that the only thing that mattered was level from side to side and that it didnt matter how the car was sitting front to rear. I went by the book though. We mated the two up, rechecking all our measurements and levels, and zipped it together. When we mocked up the front sheet metal the front frame horns are damn near in the middle of the grille opening! Thats when I got spooked. These things are 6-8 in. higher than the originals were. I could understand that kind of difference if we had added kick-up to the frame or something, but we didnt. Do these subs just point up that much to begin with?
yeah, they do. The way those "modern" cars are built, the frame under the body sits very low to the ground, and the bumper supports sit up pretty high. On the old 40s cars the bumper is about in line with the bottom of the car.
That looks just like the beauty I butchered up (eyes beginning to water)..... Well if it sounds like it was done correctly then I guess then its all trimming and fitting from here.
Could you cut the frame horns off the clip in front of the crossmember and weld the original frame horns back on from there forward? That way you could keep some of your "doghouse" and bumper mounts. Larry T
It is her car in the article. She actually sent me all the build articles along with a big box of cookies!!
Im going to put the original frame horns back on it. I'll have to "drop" the frame horns down quite a bit though. I cant cut very much of the subframe off at all due to the stabilizer bar mounts.
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