so long story short, Im building a track car using an aftermarket subframe that uses c4 suspension. Im having an issue with my SPC upper control arms bolting on. The company I bought the subframe from is telling me center to center on the mounting holes, its 6 3/8". However on my SPC control arms its 6 1/2" center to center. I do not have factory control arms to measure. Does anybody happen to have a car or a control arm they can take a quick measurement from?

Thank you,
Alex

 

QUICK??

I don't have an early 84/87 CA but I do have a later and using just an inch ruler neither is correct so I'm maybe of no help BUT first of all I'd be looking for a Metric dimension and more importantly the CA isn't based on an isosceles triangle but rather a scalene triangle so I don't understand maybe your mentioning centering based on the upper mounting points.

Whose suspension-member package are you using? Are your SPC CA in factory packages? Part #'s?

I didn't measure the later that I have using a Metric vernier but you mentioned quick and inch measurements so just curiously measuring one the center to center on the shim bolt centers it was 5 1/2". I find it hard to believe that the shim bolt centers early to late would differ by 25mm. Could they? Maybe but I'd be confirming everything you've got first by part # and dimensions provided by SPC.

I don't get the mention of CENTERING by the suspension member vendor.

Maybe to change the geometry of the later '88+ suspension the CA scheme changed that dramatically. I've not checked, but the C4 suspension packages that I'm familiar with and have worked around, a couple SR III packages, another from a Texas vendor and one from I don't know who were all spec'd to later parts.

Post back - it's interesting.

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I did find a dimension of 6 3/16" mentioned for another build so I'd certainly be checking everything, the 6 3/16" is center to center on the bracket mounting holes but they're on different elevations so that might alter the dimensioning checks. I quickly plotted the elevation dimensions and the 6 3/16" center to center (on the suspension bracket) and I believe that measuring center to center on the CA would likely result in a 6 3/8" dimension. The elevation difference is 1 3/4" on the suspension bracket I checked.

 

I just measured my '85 arm, its 6 and 1/4" centre to centre bolt holes.

 

Your rough dimension "mounted on the car" I'd think would confirm the dimension I plotted and the 6 3/8" that the vendor of the suspension member told the OP to use.

Here's the bracket that I plotted and used for my dimension. The OP can layout the bracket and measure. I did it very quickly on a piece of scrap cardboard, a straight edge and pencil. Using the proper tools/instruments you could be more accurate for sure.

 

awesome! thank you guys for all the information.

I am using a subframe built by flat out engineering, the control arms were in the boxes with correct part numbers.


I got ahold of SPC, they told me somehow my control arms got the wrong mounting shaft put on them and are going to mail me the correct part. I have no idea how that even happens on a mass produced part by a massive company like SPC. I thought for sure it was the subframe. both companys were great to deal with tho, I would buy from both of them again. I think its time to buy a lotto ticket lol


thanks again!
Alex

 

Are all C4 6 3/16's? I bought a frame and the boltholes are roughly 5 1/2" Not sure why, i thought all C4's were the same... Can anyone help??

 

'84-'87 is 6 3/8" c-c
'88-'96 is 5 1/2" c-c

 

Did Chevy just change the rods? Or are the a arms completely different? I found the rods on e bay pretty cheap. But if they are different I am going to have to buy the entire thing.

 

You bought what for a frame? You might explain what you're doing.

Upper/lower control arms & spindles need to be a match for the frame fabrication. You can NOT mix/match early or late.

 

 

LOWERS ARE NOT ALL THE SAME - NEITHER ARE SPINDLES - NEITHER ARE UPPERS - THERE'S NO SIMILARITIES BEYOND MATERIAL YOU COULD SAY!!

If you've a fabricated chassis intended for late then you need all 'late' components!