I'm dialing in my camber, caster and toe and need longer upper A-Arm bolts for my 1968 Corvette. Googling around, I can only find what looks to be stock length. These bolts are press-in style, just like wheel studs.

 

The only reason they are press-in is so that the bolt will not spin when the front-end alignment guy is trying to loosen the nuts to do the alignment. Just use some Grade 5 bolts of the desired length and then put 2 tack welds on the bolt heads to secure them from spinning. Don't use Grade 8 bolts, as the welds will crack if you attempt to weld them.

Lars

 

You may want to consider heavy duty wheel studs. They are knurled and very strong.

 

If you need to add that much caster to get into spec, you will be adding too many shims. There are upper A-Arm mounts that are slotted to add more caster, or SPC adjustable A-Arms that use zero shims.

Consider also that your frame may be bent. A strut brace might help keep the shock mounts apart, but it might fully correct the issue.

 

All great info. Thank you gents!

 

There is a frame horn to frame horn measurement to check your frame there. Measure between the last shim and the frame horn, across to the same spot on the other side.
It should be 26-3/8"
Mine is too big by another 3/8" and I am having the same problem you are. I have 1 whole inch of shims everywhere, and almost no stud left.

 

Frame to frame outside measurement is 32-7/8
Let's ALL get on the same page if you are measuring things.
This is from a 1971 chassis manual

 

It is unlikely that dimension will change much whether the frame has sagged or not. The distance between the shock towers at the UCA bars is what matters. That's what the shock tower brace tries to stiffen.

 

Ditto on the others. Check your frame first.

 

Here are some additional frame measurements;
The above 1969-1972 diagram in post #7 is excellent

The 1979 AIM adds some GM diagonal measurements, which are very helpful. And a front lower ball joint measurement. (The frame is 95% the same except for the very last crossmember where the shock absorber bumper mounts.)


Here are two which were determined by the C3 community.
The first one is published several places, IIRC the Wilcox site, but this is the only pic I could find quick.
Front crossmember Tower measurement
26-3/8" between the shock towers. This one frequently seems to change due to frame sag. This is the spot that the shock tower camber brace goes and that really seems to help. There is a lot of flex here.



Here is another measurement of the spacing between the lower a-arm mounts. They also seem to vary.
So a couple years ago we took a 12 frame survey. Here are the results:
Make your own conclusion, but it seems like they should be parallel, and few are.
Sorry this one is in mm. The "nominal" 408 mm measurement turns out to be 16.1 inches.. 406.4 mm would be exactly 16.0 inches. They just weren't that close.


All this stuff is easily checkable with a tape measure. As David Howard says, if you are within 1/4", that is probably as close as it ever was when it left the factory. (Mine was worse than normal. It must have been liquid-lunch friday!)

He has also measured at least two brand new NOS frames. He knows all the little minutae differences from year to year. He is currently proto-typing some front adapter brackets to let you use 74-82 frames on a chrome bumper car. A rear conversion may also be in the works later. He is a close friend, and it is a shame he rarely posts here anymore. It's our loss.

So I'll be his voice of experience if that is OK.