Pál_K
Cameras. I has it.
Volvo and Cadillac also participate in such types of races. You can take anything and modify it enough to "work".
In serious racing such as Formula 1, Formula 3, Indycar, LeMans (LMP cars), there is no rear engine design, never has been, and never will be, and for good reason - it's an inferior design with inherent problems.
Porsche deliberately gave the mid-engine Cayman a less powerful engine so as not to cannibalize 911 sales. You'll notice the higher-end, higher performance Porsche GT and 918 are mid-engine.
haha 
The 'Cadillac' race car is actually a mid-engine racer, chassis by Dallara, engine by ECR (a race engine builder for NASCAR) with a Cadillac badge and some GM parts.
Porsche has made many dedicated race cars with rear engines (not talking about street cars that have been modified for racing) and they've won untold numbers of races.
One example is the 935, which actually won the 24 Hours of LeMans overall. Rear engine racers swept the top four, three 935s and a 934 in fourth.
The 'Cadillac' race car is actually a mid-engine racer, chassis by Dallara, engine by ECR (a race engine builder for NASCAR) with a Cadillac badge and some GM parts.
Porsche has made many dedicated race cars with rear engines (not talking about street cars that have been modified for racing) and they've won untold numbers of races.
One example is the 935, which actually won the 24 Hours of LeMans overall. Rear engine racers swept the top four, three 935s and a 934 in fourth.
The Cayman GT4 actually has more hp than the 911 (both start at about $100K) but not as much as the 911 Turbo (which starts at about $170k.)
Pál_K
Cameras. I has it.
That was Group 5 class, - a "production" class - not a class where designers are free to develop the very best design (and which is why I specified LeMans Prototype, the very top class, as being not rear-engine). I could win Group 5 in a delivery van.
haha
The 'Cadillac' race car is actually a mid-engine racer...
I rest my case.
No one is arguing that a mid-engine design isn't ideal, but it is useful to point out that there are indeed dedicated factory race cars that are rear-engine, and they have been quite successful against other designs. In the year the 935 swept the podium at Le Mans it beat every mid-engine racer.
In the case of the Cadillac, it's actually not 'modified to work'; it's just a logo (accompanied by a big check.)