engine angle

[Tom Broome]

Originally Posted by Mike Savelle

No big tires for me , its a stock eliminator small block Camaro, and I finally got it to 3 degrees. what does the broken back mean? Thanks for all the replies

Due to the increased diameter of big tires, the axle centerline sits lower in the car than original. Essentially the car is lowered in the rear. The drive shaft has to travel "uphill" from the transmission to the pinion. We tend to want the pinion to driveshaft angle smaller on the upper plane for drag racing, think "positive pinion angle". You end up with the shallow driveline angle on the upper plane at both the transmission and pinion, forming a very shallow "U" or broken straight line, the driveshaft breaks upward at the transmission and again at the pinion. I have a friend that refers to that condition as the "skip rope angle". Not good. Doesn't "broken back" sound easier?

Ideally, you should be able to draw a straight line from the front of the crankshaft, through the transmission, and straight on through BOTH pinion bearings. That way, when you adjust the driveline/pinion angle at the axle housing, the included angle above the pinion is equal to the included angle BELOW the transmission. That way, just like the referenced guide, the "uncancelled angle" is zero.