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Discussion Starter · #1 · (Edited)
in September of 66, Chevrolet published Engineering Service Letter CEC Ref. ECR 81781 to correct an Akermann issue on police cars. While I'm still trying to get a full copy of the service letter, I have summarized a 5 page thread from another forum into the following two solutions:

Solution 1 ("90%"):
67 Center link
67 Idler Arm
Idler Arm Spacer
Template from the service bulletin (locates the 67 idler arm to work with 65-66 pitman arm.

Solution 2:
67 Center link
67 Idler Arm
Idler Arm Spacer
67 Pitman Arm
No template. Relocate Idler Arm mount off of crossmember.

Holley is making suspension parts in the USA under their Proforged brand. They have a very high quality idler arm for about $50.
Part Number:
102-10069
Holley doesn't have a center link yet. Not sure of the quality, but I sourced mine from Classic Industries.
Part Number:
DS756

I chose to go with option #2, so I sourced a 67 pitman arm on eBay.
GM Part Number:
3900559 A
There may be other part numbers for the 67-70 pitman arm, but I know this one to be good.

Made the spacer today. Had to make a transfer punch. Used 7/16 drill stock turned down to match the idler arm mount holes. A quick heat tread and oil bath, and viola, center punch ready for duty.

The spacer is made from cold roll, with 3/8-16 tap drill (O) holes, but didn't tap the holes yet. Instead, I made a pair of locater pins so the idler arm and spacer can be located and clamped to the frame for welding. The plan is to weld the spacer to the frame, then drill through the frame, and tap the holes at that point.

The car and new frame are going to the body shop soon. The spacer will be located and welded with the frame mounted and leveled on the frame rack. Will post more pictures soon.

Spacer:
Wood Rectangle Gadget Font Beige


Locater pins:
Wood Writing implement Rectangle Office supplies Writing instrument accessory


Spacer and idler arm bracket with locater pins:
Wood Rectangle Bumper Hardwood Toy


How it will eventually look. (From another forum):
Motor vehicle Light Automotive tire Hood Automotive lighting
 

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From my own experience I went with option 2 in addition to the 67 Steering arms which are a little longer. And a NOS Moog idler arm.



I did not use the template but setup all parts on chassis and then welded the spacer to the frame after it was drilled and tapped.
 

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Discussion Starter · #3 ·
Do you have a measurement on the arm from the rear mount hole to the tie rod hole? I’d like to see if there’s any difference between the 67-70 Impala and the C3 Corvette.

A shorter arm will produce more degrees of steering to center link movement than a longer arm. I wonder how this would translate into steering “feel.” Shorter arms my be desirable.
 

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Just saw your post about starting the thread... guess you beat me too it, I didn't get many pictures when adding mine.. but I can take a couple how it sits now.





The 67 arm seems to be about 5 1/2" from center of the mount hole to the center of the tie rod hole. Which gives the steering a straighter line when moving unlike the 66 arms which are shorter.

 

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Discussion Starter · #5 · (Edited)
Thanks for the measurement. The C3 arms are 5 inches from center of rear spindle hole to center of tie rod hole. I didn't measure the drop, but they don't appear to drop as much as the Impala arms.

My center link arrived today, so I'm all set. Just waiting to get it on the frame rack to make sure everything's square.
 

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Wow. Sam/Ted, thanks for your input and information consolidation here, it's fantastic! I've been wanting to do this so badly but can't find the time. (car drives just fine)
So without the template to help locate the new idler arm location or bolt holes (like them going in the frame) wouldn't it be difficult to guess-timate the new location using that pre-assembly mock-up scenario? That worries me, If there's a chance I would screw it up I most likely will.
 

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I did mine with everything assembled with the car on a 4 post lift, with the steering a straight as possible measured the center link the it was parallel to the frame and tacked the spacer to the frame. Lifted the car off the ground and then made sure I could turn the steering and made sure there was no binding. Seemed OK.
 
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