View Full Version : 1970 Big Block orientation


SF1970SSRS396
Nov 22nd, 06, 09:30 AM
Hello all. I have a question regarding the positioning of an engine in a 1970 SS396 car.

The car currently has a small block in it while the 396 is being rebuilt. I've noticed that when looking down into the engine compartment longitudinally from the front of the car, the small block sits slightly angled towards the driver's side of the car, perhaps at 3 degrees or so. I've checked the motor mounts and they're the same and fit onto the frame mounts as they should. At the transmission and cross member mount, all holes line up at the frame and at the transmission. When viewed from underneath the car, the rear of the transmission is angled towards the driver's side. It looks odd, but strangely, all holes are lined up,


I recall reading that cars which originally came with big blocks had frame mounts which sat the engine lower into the frame. I've also read that others think that big block frame mounts move the engine slightly forward. But, I also recall reading about 20 or years ago, that the main difference with big block mounts is that they position the engine and transmission slightly off the longitudinal center line of the car to compensate for the higher torque output of big block engines. Some have stated that the big block engines and Z/28 LT-1 engines shared the same frame mounts, but according to the factory assembly manual, this isn't so. The assembly manual states that all small blocks (including the LT-1) used the same frame mounts and that big blocks used different ones.

Can any one confirm any of this? Thanks to all for your time.

TJS69
Nov 22nd, 06, 11:13 AM
I'm not 100% sure if Second gen. cars are the same as 1st gen., but in a first gen. Big Blocks are offset for clearance issues by the steering box. 2nd gen. cars are "front steer" and have the steering box much farther forward on the frame. If it were a first gen. car I would say that you have offset big block frame mounts and a small block transmission crossmember. As the crossmembers are different between small and big blocks in 1 st gens.

You might want to check over at http://www.nastyz28.com. for more 2nd gen. info.

SF1970SSRS396
Nov 22nd, 06, 02:34 PM
I'm not 100% sure if Second gen. cars are the same as 1st gen., but in a first gen. Big Blocks are offset for clearance issues by the steering box. 2nd gen. cars are "front steer" and have the steering box much farther forward on the frame. If it were a first gen. car I would say that you have offset big block frame mounts and a small block transmission crossmember. As the crossmembers are different between small and big blocks in 1 st gens.

You might want to check over at http://www.nastyz28.com. for more 2nd gen. info.


Thank you TJS69. I don't know if there is any distinction between cross members for big blocks and small blocks. I do know that TH400 cars (which this car is) had a different cross member from those equipped with either TH350's or manual transmissions. But I definitely recall reading or hearing about the offset angle for big blocks to compensate for torque. Thank you again.