Help with 70 Z28

[Lynn]

I think they are right on the money. That forging number is not the part number.

Just like 186 sbc heads; all 186 heads have the same casting number, but they may be different part numbers depending on whether they came with 1.94 intake valves or 2.02 intake valves. They start as the same casting but are machined differently.

I had a couple of pitman arms with the same forging numbers; but two different size holes for mounting to the pitman shaft.

[ronzz572]

Originally Posted by Lynn

I think they are right on the money. That forging number is not the part number.

Just like 186 sbc heads; all 186 heads have the same casting number, but they may be different part numbers depending on whether they came with 1.94 intake valves or 2.02 intake valves. They start as the same casting but are machined differently.

I had a couple of pitman arms with the same forging numbers; but two different size holes for mounting to the pitman shaft.

I'm going to agree with Lynn here. There should be 4 different Pittman arms that share the same casting numbers. 2 Longer arm for Z28 specific 1 manual steering 1 power steering. And 1 shorter manual 1 shorter power steering for standard non z28 cars. All should have the 881 casting. Identifying them will require measuring them. I see no other way to identify them presently.

[Steve Shauger]

Pitman arm use has been discussed on first generation Camaros, and second follows the same discipline:


For instance the 227 casting # is for the fast ration (5.8 ") and is used for both power steering and manual. however the splined holes are different diameters. The manual steering box has a smaller shaft and PS has a larger shaft.


Here are good links explaining Pitman arm lengths and uses:


https://www.yenko.net/forum/showthre...ghlight=pitman




https://www.yenko.net/forum/showthre...ghlight=pitman

[BCreekDave]

FWIW, some photos.

Photo of the shaft diameter difference between a PS and manual box. The calipers were set off of the PS shaft. The minor diameter (diameter closest to the nut) looks to be pretty close on both pitman arms. The difference is in the taper of the shaft. The PS shaft has a much greater taper so the the other side of the spline hole is much larger on the PS '881 arm compared to the MS '881 arm. The calipers are showing this difference.


Photo of the pitman arm markings from a 1970 Z28. Power steering arm on top and manual steering arm on bottom. The manual steering arm is stamped with a letter "M" at the spline area. Arms are identical length with only difference the spine diameter size.