The first version of the radius...
The first version of the radius rod was supposedly introduced to the production line on December 15, 1966 (12C) and used a round bar. This housing came from a 01D (built during the 5th week of January) SS has a small-block and automatic trans.
In the last installment of Resto Shop, we covered a mono-to-multi–leaf spring conversion. In order to combat the effects of the less-than-stellar mono leaf springs coupled with the non-staggered shocks (a double whammy for the ’67 Camaro), Chevy engineers came up with the radius rod. It helped reduce leaf spring wrap-up and wheelhop. This design worked well enough to carry the Camaro through to the ’68 model when Chevy started offering multi-leaf springs for select models and was able to retool the plants for the staggered shock design.
There were two different radius rod designs for production use. The first production design was a round radius rod that, according to research, started being installed at the plant on December 15, 1966. The second design went into production in May of 1967, with a rectangular rod and an additional travel-limiting bracket, which limited the amount the pinion could lift while the mono leaf spring was being twisted out of shape during hard acceleration. There were definitely designing and production changes being made prior to December because we have seen vehicles with original housings with the radius rod bracket, but no provision in the floorpan for the body bracket.
David Boland’s ’67 Yenko Camaro...
David Boland’s ’67 Yenko Camaro has a 05D production date, so it came factory equipped with the radius rod. His car also has a set of crude Harrell/Yenko-produced traction bars made of bar-stock steel and the stock lower shock plate.
This the front bracket of...
This the front bracket of David Boland’s big-block four-speed ’67 Yenko which shows how the bracket bolts to the side of the framerail and the floorpan on the passenger side under the rear seat cushion.
A close-up of the radius rod...
A close-up of the radius rod travel-limiting bracket shows how it mounts to the axle bracket. It has a rubber bumpstop in its cup to soften the blow when it contacts the rod during hard acceleration.
There was also a Service Bulletin retrofit kit for Camaro owners with driving woes due to the lack of a radius rod or were equipped with the first design without the limit bracket. This kit later changed to swap to the rectangular bar and limit bracket for Camaros previously equipped with only the round radius rod. The kit included instructions on how to weld the body bracket to the framerail if it didn’t have the post-December production mounting locations and also showed how to weld the axle bracket to the housing.
Production use of the radius rod was only listed for higher-optioned V-8 Camaros. Factory use of both round and rectangular bars was mostly regulated by drivetrain equipment (with some irregularity) and continued throughout the production run of ’67 models at both plants.
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