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Old 02-21-2018, 12:39 PM   #1
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cal30_sniper's Avatar
Join Date: Jan 2011
Location: Coastal NC
Posts: 276
C20/C30 Bolt in vs U-bolt lower control arms

I'm getting ready to do a full front end rebuild on my 86, and was toying with the idea of upgrading to the F42 style heavy duty front suspension on my C20. In a general sense, I'm looking for input on whether there's any noticeable strength difference between the F42-style bolt in lower control arms, and the standard U-bolt attachment lower control arms. The F42 style bolt in control arm shafts are obviously stronger, or they wouldn't have offered them, but how much so?

From what I can gather for 73-91 trucks, the standard single wheel C20s and C30s got U-bolt style lower control arms with 6454 spec front coil springs (10" installed height). The dual wheel C30 trucks seem to have gotten U-bolt style lower control arms (possibly with welded in reinforcement plates) with heavier duty 6560 coil springs with an 11" install height. Then there appears to be an even heavier duty option (RPO code F42) that came with special bolt in lower control arms with welded in reinforcement plates, along with the 6560 spec 11" install height springs.

My 86 is a C20 with the factory HD towing package that included the larger C30 style brakes, 6454 spec springs, and 14bolt full float rear axle. I've since upgraded to hydroboost. I'm really looking to beef up the front and rear springs, and possibly upgrade to the F42 style lower control arms (which are available from Moog). I'm running an 8.1L and NV4500 combo with a grill guard up front, so I think I have enough extra nose weight to take advantage of the higher/stiffer 6560 front springs. They'll also match up better with the 10klb 24ft trailer, weight distribution hitch, and air lift rear bag setup that I tow with. I also use it for desert/mountain offroading that can get quite rough (locking diff in the rear to help out with that kind of stuff)

Looking for any and all input for people who may have looked into this before for towing/HD applications.
86 Chevrolet K20/30 Suburban - 8.1/NV4500/NP205/Dana 60/14 bolt FF, build in progress
73 Formula - 400/Doug Nash 4+1, resto on hold
86 Chevrolet K30 3+3 - 350/TH400/NP241, Air Force/Forest Service Rescue Truck, for sale
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