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#1
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Square vs round trailing arms
I’m looking at suspension upgrades for my 67 GTO. I need adjustable upper rear control arms to correct pinion angle and plan to upgrade the lower arms right away. I’ll be running a rear sway bar and I’m wondering if the torsional twisting will cause issues on round lower control arms in the long run? Im looking at UMI pieces and between their round lowers or fully boxed lowers.
https://www.umiperformance.com/home/...trol-arms-kit/ https://www.umiperformance.com/home/...trol-arms-kit/
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1967 GTO, 432 (428+.030), 4-bolt mains, factory Nodular crank, scat rods, icon dished pistons, Lunati HR 243/251@.050, .618/.622 lift, Edelbrock 72cc round port heads, 10.5:1, offy 2-4 intake, Edelbrock 650cfm carbs, Super T10 trans (2.64 first), BOP 10 bolt w/ Eaton posi and 3.36 gears |
#2
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I ran the UMI adjustable roto joint upper arms in my 66, nice product. For lowers I just boxed in the factory arms and installed poly bushings. That setup worked well and eliminated any wheel hop.
Sent from my SM-G965U using Tapatalk
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68 Firebird-- Street/Strip - 400/461 Eagle Forged Bottom End & Ross Flat top pistons. KRE 325 CFM D port, Ultradyne 263/271 @.050, .4267 lift. Crower Solid roller lifters and 1.65 stainless rockers. Quickfuel 1000 on Torker2 intake and 2" open spacer. Hedman 1.75" headers. TH400 w/brake. Ford 9" w/3.80 gears & 28x9 Hoosier pro bracket drag radial. Best ET: 1.35 60ft, 6.29 @ 107.20 mph, 9.99 @132.33 mph. 3,300 race weight |
#3
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My lowers are currently boxed but I’d prefer to replace them vs continue running 50+ year old suspension components. My goal is to replace and upgrade my entire suspension over the next few years.
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1967 GTO, 432 (428+.030), 4-bolt mains, factory Nodular crank, scat rods, icon dished pistons, Lunati HR 243/251@.050, .618/.622 lift, Edelbrock 72cc round port heads, 10.5:1, offy 2-4 intake, Edelbrock 650cfm carbs, Super T10 trans (2.64 first), BOP 10 bolt w/ Eaton posi and 3.36 gears |
#4
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Round section will twist less.
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#5
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What are you going to use the car for? It'll matter less on a car you plan to cruise than on a drag car that you're trying to get into the 9's.
I have UMI front arms on mine. When I replaced my suspension, I don't think that UMI offered the squared ones for the rear, so I bought a set from PMT Fabrication. I was coming off of what I thought was a suspension failure at 65 mph (later determined to be a rear end failure), so I felt more comfortable with the square ones that "looked beefier."
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1965 Pontiac LeMans. M21, 3.73 in a 12 bolt, Kauffman 461. |
#6
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Quote:
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1967 GTO, 432 (428+.030), 4-bolt mains, factory Nodular crank, scat rods, icon dished pistons, Lunati HR 243/251@.050, .618/.622 lift, Edelbrock 72cc round port heads, 10.5:1, offy 2-4 intake, Edelbrock 650cfm carbs, Super T10 trans (2.64 first), BOP 10 bolt w/ Eaton posi and 3.36 gears |
#7
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I’ve had round BMR Fabrication rear adjustable uppers and lowers and their 7/8“ sway bar on my car since 2002. No issues that I’m aware of.
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frittering and wasting the hours in an off hand way.... 1969 GTO, 455ci, 230/236 Pontiac Dude's "Butcher Special" Comp hyd roller cam with Crower HIPPO solid roller lifters, Q-jet, Edelbrock P4B-QJ, Doug's headers, ported 6X-8 (97cc) heads, TKO600, 3.73 geared Eaton Tru-Trac 8.5", hydroboost, rear disc brakes......and my greatest mechanical feat....a new heater core. |
#8
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I have the round UMI rear lowers with no sway bar. Very nice quality and I got the black ones. They look pretty inconspicuous and were cheaper than stock boxed. Supposedly stronger according to UMI. If you have stock boxed you could just replace bushings.
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Chris D 69 GTO Liberty Blue/dark blue 467, 850 Holley, T2, Edelbrock Dport 310cfm w Ram Air manifolds, HFT 245/251D .561/.594L, T400, 9" w 3.50s 3905lbs 11.59@ 114, 1.57/ 60' |
#9
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I put the round UMI lowers on my '67 with the UMI anti-sway bar. Nice combo, black looks cool, and really leveled out the ride. I take it on the Tail of the Dragon every year and what a difference.
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461 Stroker Built by Me - |
#10
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I have the UMI round non adjustable top and bottom with swaybar. Rear suspension is stiff as a ministers peter
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468/TKO600 Ford thru bolt equipped 64 Tempest Custom. Custom Nocturne Blue with black interior. |
#11
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We started years ago with a set of swap meet sourced adjustable Hotchkis Adjustable Uppers and have progressed to the Boxed UMI Lowers and Hellwig Bar.
Car is driven an average of 1,000 miles a month and is 'thrashed' at auto-crosses and through the mountains. https://www.hotchkis.net/product/196...&md=1089&sm=20 https://www.umiperformance.com/home/...boxed-premium/ https://www.hellwigproducts.com/prod...artnumber=5800
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1966 GTO Resto-Mod. 2nd owner California car, factory Air, Power Windows, Holley Sniper Quadrajet, MSD Dual-Sync, Gearstar 200-4R, Yank 2400 Stall Converter, HGM Compushift Mini, Heidt's Tall Spindle, UMI Control Arms, Hellwig sway bars, CPP Big Brakes, AR Torque Thrust M, Continental Extreme Contact DW |
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