LT1 vs 351 Boss

A matchup is in the January 2010 Hot Rod magazine to definitively set the record straight on the big debate in the late 60s and 70s. The competition really started with the Shelby 289 vs my favorite 327 (375hp fuelie) then moved to the 302s to end with the 350 vs 351C of 1970 & 1971, the year of our interest. Both manufacturers for the LT-1 350 and Boss 351 rated hp at 330 as did DeTomaso using the same 4” bore and similar strokes (3.48 & 3.50) on four bolt mains. Each generated their power numbers differently. Chevy went with lower compression of 9:1 by larger chambers 74-76cc for a better burn swirl instead of Ford’s 11:1 closed chamber 64-67cc and longer rod length by .078 giving Cleveland a better rod ratio. Ford ran slightly larger exhaust valves (1.71 vs 1.60) because their heads flowed better. Cams were solids but the blue oval used less duration and lobe separation. The tests balanced the environment by using the same 750 Holley carb with stock intakes. Similar headers too leveled the tests.

What about results?
LT-1 got 359 hp at 5,900 and 376 lbs at 4,100. Boss 351 with 4V heads made 383 hp at 6,100 and 391 lbs at 4,000 to win. Cleveland’s big valves and ports work well in the lower rev range when coupled with the right cam. Remember 351C used the stock cast 70 4V intake for flow rates of 274In/176Ex against the aluminum dual plane hi-rise on the LT-1 flowing 217In/151Ex. A couple of hundred rpms on the road course straights can make a huge difference on your lap times and 25 lbs can help pull you out of the turns earlier.

Pickup the mag and learn about the 289 hipo vs the early 327. You’ll then understand why Ford had to develop the Cleveland heads. Oh, be sure to give me your 4V heads as you abandon them for them new fangled shiny heads. (I wish I had a 302 to make a 400hp screamer too.)

December 11, 2009