Convoy Rubber Duck Mack

What engine powers the Rubber Duck's Mack?

It depends on what u mean, because there were 2 or 3 trucks for the movie and I dont think they were identically speccd, but if my memory serves me correctly the main truck was a 320 thermodyne, which in Oz was an ETAZ 673. However for the movie they dubbed over the sound of a 12V71. Thats what I've been led to beleive for quite awhile now. It certainly sounds like a 12V71 or a Detroit of some description. Thats what I think. Regards jeff.

8V71T, there is a seppo who has a web site dedicated to the film, maybe try Googling it.

Nearly right,......but wrong! Was actually a trick question.
In Convoy, they used 4 Macks; 2 of which were "mock ups" / stunt props / in cab shots.
Truck 1 was a brand new 1977 RS700L with a 315hp "Tip Turbine" Mack motor.
Truck 2 (the other usable "double") was actually a 1970 model, had a Cummins 855 335hp motor.

Here's the trick, the Director Sam Peckinpah thought the sound of a Detroit made a tougher impression on film. The sound of the GM you hear is an 8V-71T the Sound Recordist's put in after spending 2 days taping the audio from the KW K-Series tow truck that also made brief appearances in the movie!

got ya ears on rubber duckyhttp://1.bp.blogspot.com/_2mBmd47e5jI/SbBjDRw1oAI/AAAAAAAAANs/8BJRoGQTY5w/s320/mack3

If you're interested in the background info of Convoy, go to; stlouisdumptrucks.com.
Was very lucky to go to St Louis, MO late 2008, and spent some time with Dan Bruno and his family. Really great people, and scored a ride in the RD Mack! Was fantastic and really interesting to learn about the trucks in the movie.
Dan also - until November '09 - owned one of the 4 Peterbilts used in Duel. He is a really is a truck "freak"!