1971 Big Block questions?

[Dom F.]

Hi, I have some questions that I was wondering if anyone could help with. I own a 71 454/4spd Coupe, when the car was appraised the apraiser said it had the heavy duty suspension package(I think he called it a Gyn package?. It has the 7 leaf rear spring and a 9/16th diameter swaybar. Also the gearing is 3.55:1(I rotated the tire and counted the driveshaft revs). I thought all the 71's came with Posi rearends, but mine is a limited slip(the caution tag is on the filler), there is also a warning sticker in the jack storage compartment about the car being equiped with the limited slip rearend. Was this an option? Also the stampings on the Diff are as follows 2CAN 11 11 69 W, the CAN only coresponds to the late 69 and 70's for the 3.55 limited slip in the NCRS guide. the car has a build date of june 4th 1971, the block is number matching and the casting date of the block is Dec 4 1970, also the intake has a casting date of May 11 1971. The original gas tank had been changed by the original owner, so if there was a tank sticker it is long gone. I have seached under carpets, seats etc..to no avail, so I am trying to piece together the options. Any help with this would be greatly appreciated.
Thanks,
Dom

[Joe L.]

Re: 1971 Big Block questions?

Dom-----

Heavy duty suspension was not available during 1971 except as part of the ZR-1 and ZR-2 packages. The ZR-2 package also included the LS-6 425 hp engine. I doubt that you have the 425 hp engine, so there's no way that the car could have come with HD suspension. Only 12 ZR-2s were built for 1971 so, as far as big blocks go, those were the only cars with HD suspension. "Gymkhana" suspension, or RPO FE-7 was not available until the 1974 model year. The 9/16" rear sway bar was used for all 1971 Corvettes with big block; it's not part of any suspension package; it's part of the big block engine "package". As far as the 7 leaf spring goes, my guess would be that someone changed the original 9 leaf for this one. The GM SERVICE replacement spring for all 63-74 Corvettes was, for many years, a 7 leaf spring.

Your differential unit is not original to the car; it's been replaced, too.

"Limited Slip" is synonymous with Posi-Traction---only the name was changed. By 1971 the units were being called "limited slip" on the tags, so you have the right ones and correct "nomenclature".

[Dominic Flamini]

Re: 1971 Big Block questions?

Joe,
Thanks for the info. When the car was stripped for re-paint I noticed that the right aft quarter panel and fuel tank, had been replaced from a previous accident. It makes sense that if they bought a replacemant spring assy from GM they would have received the 7 leaf unit.