Pinion Angle Questions

[bobcowan]

Pinion angle is measured against the drive line angle, not the horizon. This is an important concept, and the key to getting it right. For every little bit you're off, you lose a little bit of power.

I would not recommend measuring the drive line angle at the carb or intake. Too much chance for error. The easiest place is the front of the harmonic balancer. On a quality balancer, that should be a flat surface, parallel to the crank shaft.

Place a digital level across the front of the balancer. Then place it across the front of the pinion input flange. Those two angles should be about the same; depending on the type of rear suspension you have. For IRS, you want them exactly the same. For a stock rubber suspension, you'de want about 3-4* of down angle.

You also want to check the pinion angle in the lateral plane as well. This is a lot more difficult to do, especially with IRS. The easiest way is to make both the drive line and the diff are straight in the frame. If they are both perfectly straight in the frame, they will be aligned to each other. But if the axle is 2* to the left, and the driveline is 2* to the right, that's 4* of pinion angle. You won't hurt anything, but you'll lose power and efficiency. If the axle is off by 2-4*, the car will crab down the road.

A quality U joint can handle about 14-15* of misalignment. Any more than that and you start to get small vibrations. Not dangerous but can be annoying. for big angles, you need to use a CV type joint.