demonpixel

iTrader: (19)

I posted this in a Pontiac forum but a friend of mine suggested I post this in here in the Conversions section also since there are a lot of people here with a lot of knowledge regarding this sort of thing.

I'm dropping in an LS1/TH400 setup in my 72 Firebird. I have a cracked LS6 block with the oil pan on it that I used for mockup purposes to see if the oil pan was going to clear.

Well, I went to put the 70-81 big block frame mounts on the crossmember, and the bolt holes didn't line up with the holes in the frame mounts. I was talking to someone that dropped an LS1 into his 1970 Firebird, and his frame mounts lined up with the holes just fine. Here's a comparison pic:



So what we did was we chose the topmost, front hole, and used one bolt to keep the frame mount in place, loosely, but in place. Here's the one bolt on the passenger side:



and here's the driver's side:



Now the motor mounts and the throughbolts went through just fine, so we feel like the frame mounts are really close to where they need to be. But, I've never done this before, so I'm wondering how exactly do you know where to drill into the crossmember so that the driveshaft will be perfectly in line with the transmission? Not pinion angle wise, although that's important also, but side-to-side wise?

We didn't think it'd be a good idea to just start drilling holes to line it up "as close as we can." If the driveshaft is cocked too far to the left, or too far to the right, that can't be good, and will probably cause vibrations or something.

I was surprised to see that the hole patterns were so different from two second gen Firebird crossmembers. Here's how we go the block to sit with both frame mounts on (by one bolt on each side), and both throughbolts through the motor mounts (and yes the oil pan did clear without any problems):



Thanks for any help advice; I just want to make sure we do this with at least some sort of precision. lol

Jimbo1367

what swap plates did you choose? Brand and any "setback"? If the pan clears and steering clears ( lock-to-lock & level left-to-right) try to scribe bolt hoes or at least the stands circumfrinse(sp) and drill the crossmember.

Jimbo1367

any pics of how the clearence of the pan and crossmember?

demonpixel

iTrader: (19)

I got these frame mounts: http://www.rickscamaros.com/camaro-e...1970-1981.html

And I'm using these motor mounts: http://www.summitracing.com/parts/EDL-6701/

I want to make sure my engine/trans is not doing this (exaggerated for effect):



or this:



There's no setback with the mounts. I believe we had about 2 inches of clearance with the oil pan. No pics of it though sorry Jimbo.