Freight photos on Flickr

The "Freight Train" AA/GD, twin blown SB Chevy engines. Notice how both of the 6-71 blowers are driven off the front engine. This served dual purposes. First, it permitted the front engine to be further to the rear of the car, and second, it allowed the front engine to input less horsepower to the front of the crankshaft of the rear engine. These were the days before the 350-inch Chevy engines were relaeased, so they had the small journal (327-inch) crank shafts. These smaller cranks had a tendancy to whip around when too much HP was inputed to the nose of the crank. On our own "Pulsator II" AA/FD dragster, this was a very common issue, and created a "black death" on the cranks on the rear engines. The engines on the "Train" on gasoline made about 500 HP each, so technically, they had about 1000 horsepower in total. The average blown Chrysler on gas made about 900 HP at best. This was the big advantage that the "Train" had on it's competition. The "Train" had enough HP and torque to use the bigger "top fuel" drag slicks, the single engine gas dragster had to run a smaller tire.

The speculation was that it took about 200 HP to drive a 6-71 blower, so if you subtract 400 HP from the front engine (which was turning two 6-71's), you could see that it was sticking only about 100 HP into the crank on the back engine. Conversly, the back engine was getting all the benefits of the 6-71 on the engine, and did not need any HP to spin it.

Our car, the "Pulsator II" was running on straight out of the can nitromethane, and each engine made about 900 HP on Chet Herberts dyno. A top fuel Chrysler at the time was making about 1500-1600 HP. 1800 HP was more than 1600 HP, so you can see that the Pulsator had a potential "advantage" (dual unsupercharged SB Chevys weighed pretty much the same as a single blown Hemi (everything was cast iron in those days). The problem was that we could never make 900 HP on the back engine when it was attached to the front engine. 400-500 HP was about the best we could do, the vibration and harmonics kept killing the back motor. We could swap engines front to rear and the same issue was always there. It could make 900 HP on the front, and 500 when transfered to the back. The crankshaft harmonics was the big killer. On the "Train", that big rubber blower belt turning dual blowers was the worlds best "crank damper" ever invented. Of course, when the 350 Chevy SB's were introduced, they had a much stouter crank (larger journals) and this problem no longer existed. - George Klass

WW&F Freight by FerdMels