I don't think Biological Combustion would every work as the core power/fuel mechanism for any biological creature. Not only is combustion extremely destructive, the fuel would have to be very energy dense.
The biggest issue I see, is that there would be no way a biological creature would be able to maintain an environment or engine suitable for long term and consistent combustion. Combustion is hot, high pressure and destructive. You need energy dense fuel and something capable of withstanding that force for a life time. Ceramics are good, but unlike bone or antlers you have no way to repair a ceramic that has been damaged. One side has access to blood, veins and nutrients. The other side is subject to miniature explosions. So your ceramic engine heart needs to grow inwards to be able to repair itself and it needs to destroy itself fast enough so that there is still space for more the combustion to occur. This is of course ignoring that the ceramic shatters due to large impacts.
The next issue is that all of these materials are going to cost a lot of energy to produce unless your going to change the biology to something that isn't carbon based (and then its really whatever you want). Oil is extremely energy rich, and having the biological process necessary to create a spark for the explosion present from birth is going to be even harder. Your creatures are going to need a secondary digestive system just to be able to convert the wood, meat and whatever else they eat into the fuel required to power their muscles in the first place and a third system to be able to convert the wood, meat and metals into the ceramics required for your primary ceramic heart (engine).