Yes, the momentum increases, but so does the grip.
Static, rolling, and sliding friction are all directly proportional to the normal force, which is equal and opposite to weight.
So, in theory you can increase grip by adding weight. Of course this advantage is negated in racing by the adverse effects of weight, including momentum (Although, does this really matter on tracks which require no braking or hard cornering?). In terms of blowovers, added weight would require a greater lift force in order to make the car airborne.
I just wanted to give a cheeky answer to what was suppose to be a difficult question.