Okay first a few basics. Upper A arms simply connect 3 suspension pickup points,they don`t define them. The location of the pivot bushings and upper ball joint pivot ball do that. As a result upper A arms cannot make any meaningful change in geometry per se. They can only change static alignment which may result in a performance improvement. That would also be true using any other method to achieve those same specs. What the arms CAN do is allow you a wider range of static alignment adjustment. In some cases they NEED to be changed to accomodate real geometry changes that then cause the stock A arms to be a poor fit.
The 2nd Gen has a pretty decent front end in it to start with. Not great but decent. Camber gain is neutral to mmild. Roll center is roughly ground level and could stand to go up a bit to shorten the front RC/CG moment arm. Bumpsteer is pretty good especially by the standards of the day. They respond well to more postitve camber and properly designed aftermarket upper A arms or even SPC lower A arms will help with that. With very aggressive negative camber settings they can turn in impressive track performances at the expense of a very short tire life. That said GM engineers knew even in 1970 that the cars could benefit from more camber gain and recomended doing mods to achieve that in the road race section of the 1970 Chevy High Performance manual. Unfortunately the mods are quite a bit more complicated than the G Mod on 1st Gens because the 2nd Gen`s UCA perches are so much shorter. We`ve refined the geometry they achieved with those mods by moving the outter pickup point with tall ball joints and combining it with SPC adj. upper A arms to get a complimentary performance alignment. The improved geometry basically lets you enjoy the performance of full race settings while running street friendly settings with great tire life. We have a number of clients autocrossing,open and close course road racing 2nd Gens with this package who have seen a big jump in performance and how well they place. Some of our clients are even running our tall ball joints with Global West,DSE or Hotchkis arms they already had.
For a totally plug and play fit I recomend the SPC arms with the HD bushings. The greasable bushing cross shafts are a bit shorter and may require a little bit of massaging on the A arms perches for a perfect fit. We`re working with SPC to tweak them a bit for a 100% bolt on fit.
There`s no such thing as a "tall spindle" for a 2nd Gen. All 2nd Gen spindles are "tall" (using the hot rodder vernacular for any spindles taller than 1st Gen/A body or G body spindles). We do have several clients running them with AFX aluminum spindles. The tall version is about the same height as your stock ones but you can run them with our tall ball joints to achieve more the more aggressive geometry discussed above. So why run them if they`re not taller? Big weight savings, easy bolt on modern 13"+ brakes, 1" drop, huge C5 wheel bearings,about a 30% reduction in lateral roll center migration etc. They need to be run with `65-`72 A body steering arms and outter tie rod ends. For that reason we don`t consider it an official StreetComp package, although we do sell them. The Chevelle arms are shorter and give a quicker steering ratio and more aggressive ackerman for improved low/medium speed turn in. It`s particularly noticable in autocross conditions where turn in is razor sharp. It really makes the car feel lighter and more nimble. Mark SC&C
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