I've cooked marinated chicken in aluminum foil on the manifold of a small block 8 over a 4-6 hour trip a number of times (a long time ago... it's been 10 years since I've had a v-6 much less an 8.) I didn't have a meat thermometer in those days either; I just stuck it with a knife and if the meat was firm and the juice was clear, it was cooked. Eh... I lived.