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Old 02-23-2021, 01:16 PM
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Rocky Rotella Rocky Rotella is offline
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The Ram Air Super Duty (UPC LS1) was planned to be a bulletproof version of the R/A IV available in the 1970 Trans Am. A December 1969 printing of the 1970 Engine Application Chart shows codes WH (manual) and XN (auto) for it. And a Car Distribution Bulletin published about the same time announces the cancellation of the L67 Ram Air IV in the Firebird line and that a replacement engine (Ram Air Super Duty) would soon be announced.

The R/A S/D consisted of the reinforced 400-inch block with large distributor hole from the R/A V program, the forged 3.75-inch crankshaft also from the R/A V program, forged connected rods (which, like Tom I assumed were likely re-issued 421 SD rods but have no definite proof of it), and the forged R/A IV pistons. The top end was comprised of standard R/A IV components. To accommodate the larger distributor drive gear, the 041-spec number-480737 "K" camshaft was created. That camshaft later resurfaced during the development of the SD-455 for 1973, and is now referred to as the "pre-production" cam. The R/A S/D carried a power output rating identical to the L67 Ram Air IV.

Why the reason for the LS1 R/A S/D program? Beyond giving Firebird racers a bulletproof platform for competition, it may have also been a way for Pontiac to fulfill contract obligations with outside suppliers who were to produce the canceled R/A V programs forged-steel components. And by that point Pontiac may have had several dozen 3.75-inch forged-steel crankshafts in house that they needed to use up.

In early 1970 (calendar year) Pontiac stated internally that it planned to expand LS1 availability into the 1971 A-car and when that occurred the L67 R/A IV would go away entirely. By May 1970, Pontiac issued an internal memo noting that because of connecting rod supply issues the LS1 R/A S/D was canceled for the 1970 model year. The L67 would replace it in any 1970 Trans Am order, but when looking at original 1970 Trans Am window stickers or billing invoices, you'll see the LS1 UPC and references to the "Super Duty" that was originally planned.

As far as I know, no "production" cars were produced with the R/A S/D engine, but I've heard about (and believe the associated stories) that customers and/or dealers with the right connections had special "memo" cars built with the forged bottom end.

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