Accurate Exhaust

...was that 3 tenths of an increase on a stock 275 hp 340?

Yes it was. I run in the Pure Stock Muscle Car Drag Races so it HAS to be stock. We get to run any rear gear ratio, and we can upgrade the stock exhaust to a max of 2 1/2" with H and X pipes allowed. Mufflers have to be oval if so equipped from the factory, so I run DynoMax Ultra Flo mufflers.