GM Coil Spring 12 bolt EXPERTS please...?'s

[KEVINS]

As a lot of you know I designed a Mustang suspension kit and sell it as a part time gig. I have been approached several times to make one for the coil spring GM cars with 12 bolts but I "think" have design issues with them compared to the Stang 8.8's.
My question is are the UCA "Lateral" angles all the same for all GM cars? I could have sworn that there were several 12 bolts or body styles that had different lateral angles for the upper control arms.. I still don't know if I will do it but a buddy at Rhodes Custom Auto is puting together a Malibu and I am making some of the parts for this application while they make the rest. In order for me to mfr these for GM car's all of the lateral angles have to be identicle from GM car to GM car. Would a 12 bolt have the same lateral angles as our TB rear ends?

...still thinkin.....

ks

 

[1ARUNEM]

I cannot answer your question with certainty, but think that most "4 link" style 12 bolts have the same upper lateral angles. I believe it is the lowers that are different.

I also can tell you that SSM sells a control arm kit to adapt a 12 bolt out of say a 68-72 chevelle to a G body.

Perhaps you could come up with one of their kits and use it for further study..

You may try asking at www.maliburacing.com as these guys do alot of 12 bolt swaps..

I know it's not much info, but HTH..

 

[KEVINS]

That just may help!!

 

[John Larkin]

No disprespect to Warren. I read somewhere that the early rears from G-bodies (68-72 as mentioned) had a different angle on the upper ears. It might be on **** (short for Richard) Miller's site, that PDF article he has, the long one.

 

[1ARUNEM]

None taken, John. I wasn't sure but thought they were interchangeable. My knowledge on the subject is limited but just wanted to help if I could..

 

[KEVINS]

It looks like I'll have to do some heavy duty research then if I plan on doing this... hmmm......... Appriciate the info guys!!

ks

 

[turbofish38]

Hi KEVINS, I have a 12 bolt relocation kit on my 86 GN. You can read about it here: http://www.turbobuick.com/forums/showthread.php?s=&threadid=114413
The upper angle is a little different, how much I dont know because I didn't bother to measure it. The kit I used was purchased through HP Motorsports in Omaha. All A-body rears have the same angle from 1964 to 1977. I think even the B-bodies from 1977 to 1996 have the same angle too. If anything there cant be more than 1 degree difference there. I do know when I asked the boys up at METCO if they could build me some adjustable arms they mention they ran into problems trying to make thier own kits and scraped the idea. Hope this helps. It may not be to clear in my information but basically I installed a B-P type 8.50 10-bolt from a 72 Skylark under my 86 GN.

 

[KEVINS]

I just found some excellent info including UCA lengths:

'64-'67 GM A-Body
Chevrolet: 1964-66 Chevelle, El Camino, Malibu; Oldsmobile: 1965 Cutlass, F-85, 442; Pontiac: 1964-66 GTO, Le Mans, Tempest

1964-67 A-Body Bolt-On Rear Upper Control Arms
Center to center length is 12.750''.

'68-'72 GM A-Body

1968-72 A-Body Bolt-On Rear Upper Control Arms
Center to center length is 10.250''.

G body:
'78-'88 GM G-Body
What consists of G bodies?

B body:
'78-'96 GM B-Body
What consists of B bodies?

F body:
'82-'97 GM F-Body
What consists of F bodies?

Adj. Upper Control Arm, 78-88 GM A/G-Bodies
Adj. Upper Control Arms, 68-72 GM A/G-Bodies
Adj. Upper Control Arms, 64-67 GM A/G-Bodies

In a nut shell it looks like the control arms are differentiated by lengths and the year of the cars unless the lateral angles differ which would make the lengths different..

ks

 

[KEVINS]

I got it figured out with a few ph calls to Strange and Currie:

There are 12 bolts and 8.5’s. All 12’s have the same lateral angles and all 8.5’s have the same lateral angles but the 12 bolt and 8.5 have different lateral angles.

So you CAN NOT bolt a 12 bolt in a car that was equipped with an 8.5 w/o having problems.

For some reason I feel that someone is going to come on here and tell me that is what they did..

ks

 

[86brick]

Originally posted by KEVINS

For some reason I feel that someone is going to come on here and tell me that is what they did..

ks

Definitely not what I did, but I know of a few GNs that went from a 8.5 10-bolt to an aftermarket 12-bolt...... One of those guys was Terry Houston.... He had a KTRE 12-bolt in his car that ran mid 8's.....

 

[1ARUNEM]

It has been done. Everything fit exactly correct? Probably not, but some guys ( I know a couple) have gone directly from a 7.5/8.5 to a 12 bolt. Nothing is impossible for some backyard mechanics..

 

[KEVINS]

Originally posted by 1ARUNEM
You may try asking at www.maliburacing.com as these guys do alot of 12 bolt swaps..

I know it's not much info, but HTH..

Nice link..
I've spent the morning browsing the above forum and boy do they praise the SSM bars. That site is obviously sponsored by SSM....
I didn't find any "new" info but the archives verified what I have found thus far. It looks like the GN 8.5 and the 12bolts are the only rears used or recommended.

Question:
What cars do the 8.5's come in besides TB's?

 

[1ARUNEM]

I know alot of guys around here don't care for them, but I have used SSM bars with GOOD success. I also gave a set to a local buddy who is on this site. His best 60' previous was in the mid 1.50's I believe. After the install, his first time out netted a LOW 1.40 short time. They PLANT the rear to the ground..

As for other vehicles with the same TR 8.5, I believe the mid 80's Olds 442 and some Hurst cars came with them.

Goodluck..