Metric frames used as a Racing Chassis

With a lot of emails about building a race car with a metric chassis over the popular Chevelle Frame, I figured I would build an IMCA Modified using a 1995 Monte Carlo SS Frame.  I have built several Pure Stock race cars using the metric frame, and I have proven they can be winning chassis, the setups are pretty straight forward when  you cant play around with the suspensions, this pretty much limits you to designing a roll cage to give strength, and position weight were you need it, there is a tremendously dificult to get the weight to the rear of the car so its not nose heavy, When GM designed the monte carlo using the New, New, New metric frame, it was pretty much designed to be neutral (able to turn left and right in a performace stance) for the street, not for the race track.  when you strip it all down remove as much sheet metal as you can and install a roll cage in the car, you basically have something that gives you around 38 percent rear weight, even if you move the engine back to the max rule allowable, which would be placing the #1 spark plug of the motor so it is no further back then the center line of the ball joint, and using a large fuel cell that stays topped off, you will only see about 40 percent rear weight, to get the car to handle through the turns you need as much rear weight as you can get. In addition, the ride height is much higher, because of the location of the suspension arms, and the engine height compared to the older chevelle frame.  So with this said, lets look at whats going on with the metric frame.

The real deal with Frame strength, areas to strenthen, and the ever popular ROT thru, yes I said rot... eaten away by rust, caused by the manufacture using recycled steel, thinner, and untreated, it rusts through within 10 years,  First you have to understand that the metric frame is now and has been made with recycled steel, and is thinner than the older frames of the chevelle, Impala, Monte Carlo's. Frame components that are welded onto frame rails, engine cross member and front horns are welded by robotic welders which weld at a programmed rate, their speed and penetration is programmed by someone who uses an average frame with in the factory, this means that the components will fit within certain perameters allowing a little fluxuation in component fit.  Every weld I have seen that has been welded by a robotic welder is never perfect, it may be perfect for street driving, but not for racing.  In the photos below you will see some of the poor welds that the robotic welders put on a frame, and a first hand look will be evident of missed joint welds, short welds, and components not properly placed.  Its for this reason that when you decide you want to use a metric frame you need to do the following:

Sand blast the frame and check all welded joints, look for burn through, where the weld has chewed the metal up on the side of the weld making the metal thinner than it was before the weld, this is usually a thin line beside the weld. also look for welds that miss the joint all together, and welds that stop short of the end of the seam.

All the factory welds need to be inspected, you will most likely have to reweld the majority of them, and patch thin areas, don't be afraid to use a good pick hammer to test for rot thru, if you find something, keep working around the area until you find solid metal.  The more you can do to prep the area the better.  With race tracks still using calcium to keep the wetness in the dirt you need to do a frame check several times a year, this is very important, after each and every race: you must pressure wash or at least hose down the frame inside out to make sure that all the dirt that has built up is removed, I have seen many race cars with the frames rotted out at the end of  one racing season.  I can think of better things to spend money on for the next racing season other than buying a new chasiss.

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