Originally Posted by pcoghlan
My question relates to alignment between the engine/gearbox and the driveshaft/rear end. I dont yet have a driveshaft and will need to scratch my head and work out how to get one made up after the engine/gearbox is in place so I have the correct length.
Place the engine at the height you wish it to be and as far back as you wish.
Center the engine between the side frame rails. Measure this at the center of the harmonic balancer and the center of the trans tailshaft.
NOTE: Sometimes the engine/trans unit will be offset to one side to allow clearance for the steering. If this is done; the engine/trans centerline should still be parallel to the centerline of the pinion shaft.
The 'Y' block assembly is longer than the SBC so you may have to recess the firewall some.
Level the assembly using a level on the carb mount surface on the intake manifold from side to side and front to back. You will see that the rear of the engine / trans assembly is slightly lower than the front of the engine. This will be about 3 degrees and is normal.
Fabricate your engine and trans mounts at this time.
To measure for driveshaft length; install the front transmission yoke all the way in. Then slide it back out about 3/4" - 1". Measure from the u-joint bearing centerline of the front yoke to the center of the u-joint centerline of the yoke on the pinion shaft. This is the measurement you will need to have your driveshaft made. The pinion shaft of the rear third member may be offset (not centered) from side to side between the frame rails. This is OK.
Eyeball measurement is NOT
good enough. Use a tape measure. Looking from above the engine/trans, frame, rear axle assembly; the centerline of the engine/trans should be parallel
to the centerline of the pinion shaft in the rear axle assembly. They can be offset.
Looking from the side view of the same assembly; the centerlines once again should be parallel. For drag racing alignment
the rear pinion centerline may actually be pointed down from the engine/trans centerlines and not be parallel.