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Discussion Starter #1 (Edited)
I am in the process of a 502 big block swap. I installed the big block frame mounts (tall mount on the drivers side). I bought a crossmember from year one for a TH400 and the mounting pad is off to the passenger side of the transmission mount. The engine is offset to the passenger side which puts the tailshaft offset to the driver side (away from the crossmember mounting pad). Either the engine is offset in the wrong direction or the crossmember is in the wrong location. Any thoughts? I have been told that the big blocks are all offset towards the passenger side but does this mean that while facing the engine (A) the passenger side front corner of the block is closer to the frame rail than the drivers side or (B) the drivers side corner of the block is closer to the frame rail than the passenger side?
 

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I just installed my bigblock with the offset mounts. And a TH400. The transmission is offset to the drivers side 3/4" inch. The engine itself is offset to the passenger side. I used a new crossmember also.


I will be interested in what others say.


Dale
 

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Discussion Starter #3 (Edited)
Is the engine supposed to be parallel to the frame rails but offset to the passenger side or "twisted" with the front of the engine toward the passenger side and the tailshaft towards the drivers side?
 

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When I put the 400 trans in my small block car, the crossmember I got from Chevrolet didn't fit worth a damn--I ended up slotting the holes on both sides so I could get it centered. It could be due to my using a Camaro crossmember because the Nova part wasn't available, but I figured it would be close enough.
 

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The pinion is offset on my 72 Nova by 3/4 inch. The engine and trans will be offset to the passenger side so the driveshaft would be even to the rockers back to the rearend. I'm no expert but I asked alot of questions about this offset before I welded my new moly axle tubes in the 12 bolt I built. Everyone I talked to about this said 3/4 offset and the tunnel is built offset too. The pinion is centered in the tunnel now so the outset seems correct. I also have had to slot crossmember holes in the past for the trans mount. I have no motor/trans in the new car yet so I can't say what I'll have when I get that far but it looks like it is going to work out fine. RM
 

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502nova said:
I am in the process of a 502 big block swap. I installed the big block frame mounts (tall mount on the drivers side). I bought a crossmember from year one for a TH400 and the mounting pad is off to the passenger side of the transmission mount. The engine is offset to the passenger side which puts the tailshaft offset to the driver side (away from the crossmember mounting pad). Either the engine is offset in the wrong direction or the crossmember is in the wrong location. Any thoughts? I have been told that the big blocks are all offset towards the passenger side but does this mean that while facing the engine (A) the passenger side front corner of the block is closer to the frame rail than the drivers side or (B) the drivers side corner of the block is closer to the frame rail than the passenger side?
Just a thought. Was there ever any damage to the frame?
 

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I had the same problem with a crossmember from that I bought about 8 years ago or more. I never could get it to fit right. I slotted them out but never did really fit right. Anyway, later on I saw on a website (John's website) where he had a similar problem and that it was due to a defect with a batch of crossmembers. I have since ordered a new crossmember but haven't tried it yet. Like most of my work on the Nova, it gets drug out over a few years due to many other projects :mad: .

John
 

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I had what it sounds to me the same problem in a 68 I had. it ended up that it had the wrong frame mounts in it. When I bought ones for a nova everything lined right up. But my trans was way off down at the mount.
 

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502nova said:
Is the engine supposed to be parallel to the frame rails but offset to the passenger side or "twisted" with the front of the engine toward the passenger side and the tailshaft towards the drivers side?
Ok here is my thought on this....my understanding is that GM offset the BB to get some extra clearance between the drivers side valve cover and the power brake booster...which would be at the very back of the motor on the drivers side.....So it would only make sense that the motor should be parallel to the frame rails cause if it was crocked, twisted towards the drivers side, it would negate the extra clearance that GM was trying to create with the offset frame mounts....IMO....something is outta wack ....I have always heard that the motor and transmission are offset and then the driveshaft is angled towards the rear diff...I dunno thats just what I heard:)
 

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Discussion Starter #10 (Edited)
My crossmember is in the same position as the one on Johns website!!!! I got it from Year One so watch out for those. I took some measurements last night and the motor and trans are parallel to the frame rails and offset about 3/4". I am going to re locate the pad to the correct location. Thanks so much for the help and for once something on this project isnt my fault.
 
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