speedtech LCA bolt question - Camaro with factory subframe

[c4racer2]

I am installing the Speedtech lower control arms in a factory frame - 1971 Camaro

the bolts they sent with the kit measure .54" - they are big, maybe 5/8" bolts. The hole in the frame is just over .5" - aprox .525"
these bolts certainly don't fit through the factory frame holes.

the factory bolt is just under .5" at the collar - they are probably a 7/16" bolt.
Is there any reason to use their hardware? I am not very keen to drill out the factory frame because it may need to go back to stock arms someday or maybe another supplier that doesn't use such large hardware. Plus I don't have a 5/8" cobalt drill bit anyway.

So I'm currently installing these using the factory hardware. Mine is in great shape - I see no reason not to reuse it.

Anybody have experience with this or a good reason why I shouldn't use the factory bolts?

Also - the shock mount isn't threaded like a stock arm. There is nothing in the instructions about opening up those holes or about how to mount conventional shocks - I can just use the same bolts but with a locking nut. I have a fresh set of Bilstein shocks and currently running Hotchkis springs - not coil overs.

[BlackHD]

Call speedtech their customer service is great.

[dhutton]

As far as I know they supply oversized bolts because the holes are usually enlarged after 50 years. I would not use the originals because the arm will be able to move. Use the supplied bolts.

Don

[c4racer2]

DSE has much better instructions. They say the factory subframe uses either .5” or 9/16” bolts. Not sure if that was different years or what. But the DSE uses 9/16” bolts which is probably same as the speedtech. And says to use those because the bushing is designed for them. Which makes sense.
They recommend a uni-bit to hog out the holes. Speedtech should put something similar in their instructions. I was thinking about returning them and getting DSE.

[c4racer2]

Unibit did the trick. Easy peasy.

But the hard part is getting the spring installed. These arms have such a deep spring pocket it’s impossible to get the spring to seat in both the upper and lower pockets while uncompressed. The only spring compressors I have are external and I cannot get the spring compressed enough to install it that way. I need to look for an inside the spring compressor. Seems like you have to compress the spring more than 25pct to make this work with these arms.
Stock LCA spring pockets are no problem without any compress.

[killer69]

Fixed the instructions
some of the early cars did use 1/2 bolts but the majority used 9/16" so we supply them to fit the majority

[c4racer2]

My car is a 71. So probably on the early end of things yes. Anyway no worries it just seemed like something was wrong when the very detailed instructions made no mention of that. If there were no instructions I would have been less concerned and just gone with it.

Still need to get an internal spring compressor to get the springs installed. Ordering that today. Can’t get the springs in the lower pocket without one like You can with stock arms

[c4racer2]

Btw. Side note. I ordered the T56 crossmember for second gen as well. Nice piece. Just a heads up there were no 5/16” nuts or washers to attach the sliding brackets that attach the crossmember to the frame brackets. Probably an oversight when my HW kit was assembled. But please make sure that’s on the BOM - because the instructions also don’t list those nuts either. I had some on hand luckily.