Quote from 6F07KGT
One of the times Shelby spoke at one of our NorCal events he mentioned the issues with the Ford built tunnel port engines... Shelby said the engines came to them sealed with an attached dyno sheet showing what that particular engine had produced. Shelby's team was supposed to drop in the engine and go. They were not supposed to inspect or modify it in any way.
Very interesting post...It falls in line with other accounts of the "Tunnelport era". Shelby's organization apparently built (blueprinted) the racing 289's that were victorious in the first two Trans Am seasons in 1966 and 1967. Although Ford was backing Shelby, it was not in an open way. Shelby fielded winning 289 powered Mustangs for the Teringua Racing Team as a front for the Ford Motor Company during the first two Trans Am seasons.
Ford decided to drop the "Terlingua" front and put it's full support into the Trans Am for 1968. This was a direct response to the Camaro challenge from Chevrolet, which was aimed squarely at Ford, and Mustang in particular. Since the Z-28 Camaro outpowered the 289 Mustangs, Ford's Engine and Foundry Division developed the semi-exotic Tunnelport 302 to beat the Camaro in the 1968 Trans Am. As Mitchell mentioned above, the Tunnelport engines were built by Ford, and supplied directly to Shelby.
This new racing small block engine was based on a special 4 bolt main bearing 302 block, and used a scaled-down version of Ford's NASCAR 427 Tunnelport heads. By placing the pushrods inside tubes that passed through the intake ports, the ports made a streamlined path to the cylinders, instead of bending around the pushrods. This made them breath far better than the stock 289 High Performance heads. Intake valves were enlarged to 2.12 inches, as were the exhaust valves at 1.54 inches. The potential for a considerable increase in horsepower over the "old reliable" 289 HiPo was apparent in the new design.
There was supposed to be a "street" version of this engine to satisfy the homologation rules, but it never happened. Instead, someone at the Engine Foundry Division discovered that with a few modifications, the new 351 Cleveland heads with huge, canted valves, would fit on the Tunnelport 302 4 bolt racing block. Thus, the BOSS 302 was born...