Nixon had race cars over to the white house, and fired up Richard Petty's and Mario Andretti's race cars

http://sca.gmu.edu/exhibit/atkins_1.htm

If you want to click on it for the full size and read the whole thing, that is the best way to get all teh info, but simply put, Jackie Stewart and his Lola Chevy, a dragster, Richard Petty's 1971 Road Runner stock car, Mario Andretti's Indy car were there, in the White House drive way.

Petty and Andretti fired up their cars. Wow, that would have been great to experience!

Others there, Swede Savage, Dan Gurney, Penske, Posey, Donohue and Graham Hill

From the Nixon Library:

515 to 527 pm Sept 21 1971 White House

The President viewed an exhibition of race cars. He was accompanied by race car driver Mario Andretti, winner of the 1969 Indianapolis 500 and member of the President's Advisory Council on Physical Fitness and Sports.
The President spoke briefly to the owners and drivers of the cars:

James Lee, owner

Richard Petty, owner/driver

Andy Granatelli, owner

Carl Hass, owner

Jackie Stewart, driver

535 to 645 pm
The President hosted a reception for automobile racing figures.

from http://www.nixonlibrary.gov/virtuallibrary/documents/PDD/1971/042%20September%2021-30%201971.pdf just page 3, and Appendix D actually doesn't list the racers, it says they were all issued invitations verbally and this no comprehensive list was made

See a photo of it on page 76 of "Cars of the King" http://books.google.com/books?id=Txbx3Y2mDL4C&pg=PA76&lpg=PA76&dq=1971+white+house+race+cars&source=bl&ots=sSwEUIdUS_&sig=ELJG5IhIK1YMdpjWObWP3vV8SzA&hl=en&ei=GZtiS_e9GY-ssgO_3rCdAw&sa=X&oi=book_result&ct=result&resnum=7&ved=0CCMQ6AEwBg#v=onepage&q=1971%20white%20house%20race%20cars&f=false