timing

Timing is also effected by chamber shape and plug location, on early engines with open chambers they like 34-35 and no more and the 302 heart shaped heads don't like more than 30* total. Will they take more sure but the HP and TQ will suffer. Then it depends on what kind of fuel your using, higher octanes need more lead than lower octanes do, just as compression effects the amount of timing also,so like Jack said every engine is different.