NASCAR on Tuesday took away 100 of the 175 championship points Gordon earned and fined his crew chief, Robbie Loomis, $25,000 for a rules violation discovered in the post-race inspection.
Gordon was allowed to keep his earnings of $130,220. The 100-point deduction did not affect his 10th-place ranking.
A penalty had been anticipated since late Saturday night, when NASCAR said it had "an issue" with Gordon's intake manifold.
"The General Motors intake manifold that the No. 24 team used during Saturday night's race ... has not been approved," NASCAR chief operating officer Mike Helton said in a news release Tuesday. "The GM part number on the casting was the same; however, a different material was used which altered the properties of the casting.
"The changed casting was not resubmitted by GM for NASCAR's approval in accordance with our procedures."
Rick Hendrick, owner of Gordon's No. 24 Chevy, said he will appeal the penalty. He said the intake manifold in question was not manufactured by Hendrick Motorsports but was supplied by GM.
"The alleged violation is the use of a magnesium alloy rather than aluminum in the intake manifold," Hendrick said. "GM engineers believe that the intake manifold conforms to all NASCAR rules. ... Hendrick Motorsports engineers have tested the part and determined that it in no way affected horsepower output.
"There was no attempt to conceal the part, which we have been running since April."
Gordon's violation has added significance because the Monte Carlo 400 was a Winston No Bull 5 race. Dale Earnhardt, who finished second, would have earned a $1 million bonus had he won.