LAS VEGAS -- Lee White, president of Toyota Racing Development, said some of the Sprint Cup Toyota teams have serious concerns about an engine wear issue that has caused problems the past two weeks.
White said four Toyota teams were forced to change engines Saturday at Las Vegas Motor Speedway because of the issue with this generation of the motors.
Two of the cars making changes are the Red Bull Team Racing entries -- the No. 82 Camry driven by Scott Speed and the No. 83 Toyota driven by Brian Vickers. The other two are the No. 47 Toyota driven by Marcus Ambrose and the No. 00 Camry driven by David Reutimann.
"It's embarrassing," White said. "Whatever conditions we've created ourselves, stupidly, we suspect it's a wear issue between the cam shaft and lubricant. It's either a lack of lubrication, too much lubrication, not enough coating, whatever."
The team of pole winner Kyle Busch in the No. 18 Toyota also changed an engine Friday, but White said that was an unrelated issue. All five cars will move to the back of the field to start the Shelby 427 on Sunday.
"This is something the drivers don't notice," White said. "What we see first is a lash widening up on one cylinder or the lifters slowly wearing away. Once that starts, it's hell and gone. You can't stop it."
White said the problem first came to light last week before the Cup race at Fontana, Calif.
Vickers won the pole at Auto Club Speedway, but was forced to start in the back after the engine problem was discovered. Michael Waltrip had the same issue after qualifying at ACS and changed his engine. Neither driver had a problem during the Auto Club 500.
"That clouded my view of the whole situation," White said. "I was confident in my people, but I guess I'm willing to say now we went the wrong direction."
White said all the Toyota teams have taken precautions and made changes for Sunday's race.
"We're using a little heavier lubrication to not try to squeeze every last horsepower out of them in the race," White said. "The adjustments we've made are four or five horsepower, but that's not insignificant. No driver would give that up willingly. Our goal right now is to give them the best shot to get to the end [of the race]."
White said this engine specification was run for the first time in the Dickies 500 in November at Texas Motor Speedway.
"It was a test in five cars," White said. "We had zero issues."
So does that mean something in the engine setup was changed this year?
"I'd like to say no, but something has changed," White said. "Just the simple fact that you're going from prototype quantities to production quantities is a change."
Joe Gibbs Racing -- which includes the cars of Busch, Denny Hamlin and Joey Logano -- is the only Toyota team that builds its engines in house, using Toyota parts. All other Toyota teams use engines built at TRD in Torrance, Calif.
White met with three NASCAR officials Saturday morning -- president Mike Helton, vice president of competition Robin Pemberton and Cup series director John Darby -- to explain the problem.
"I asked them if they wanted to use a cattle prod on me or maybe a .38 to the forehead," White joked. "But they are very understanding. Obviously their concern is the show and our image, which we're concerned about, and the sponsors."
White said the problem surfaces early in an engine cycle, so he hopes it won't be an issue Sunday.
""Here these engines will be running well over 9,000 RPMs for 427 miles," White said. "But once you get beyond a certain point and don't see this issue, you're golden. It's an infant-mortality thing.
"Our people at TRD have worked their tails off to fix it. We had three guys bring five engines over from California this morning. They are ready to go if we need them."
The only problem is those engines are the same generation of motors that have the wear issue. If Toyota has engine failures Sunday, White said they may switch to the old-generation motors for next weekend's event at Atlanta Motor Speedway.
"We have people inventorying our stock of the previous generation of engine as we speak," White said. "We are starting to build them in case we need them in Atlanta. Other than two tire tests, Fontana was the first time we've had these engines racing."
Cup teams use restrictor plates on the engines in the season-opening Daytona 500, limiting horsepower and putting less stress on the motors.
Terry Blount covers motorsports for ESPN.com.