Overall, which one is the superior system, taking into account the efficiency, reliability and response to modifications?

 

Well lets put a dollar value on them...
1) will not break the bank
2) will need deep pockets
3) if you have to ask, "you can not afford it"

 

What if the answer to "which one is more reliable" is not the same as "Efficient" or "responsive to Modification" In my opinion all three of those questions would get a different answer.

 

I still prefer the good old 16 valve, SBHC (single below head cam)

 

push rod engines have their benefits because they are easier to time staticly if you take the engine apart. ohc and dohc are a bit more difficult to time, especially if it wasnt lined up and locked in place. however, there are no valve adjustments need on ohc and dohc if you pull the head off, so thats a benefit. ohc spins less stuff than a dohc, but the dohc usually makes more power.

cam araingment has no effect on efficiency though
as long as its maintained, there is no difference in reliability. however typicly ohc and dohc use a belt that needs replaced every 60k miles. gm recomends a timing chain and gear every 80k, but i have yet to see anybody replace one until it breaks
repsonse to mods depends on the engine and mods

 

Looks like everything has been covered. The only thing I will add is that overhead cams have oil pressure going thru the head. This is a little harder on the oil (todays oils handle it without much problems). Also many designs are prone to oil leaks at the head gaskets. Since you have oil and coolant going thur the same gasket the chance of complete engine failure is higher in a overhead cam design. If coolant get into the oil it can strip the babit right off the bearings.

 

It's amazing how I didn't think of that, lol.

I can't really change the poll, but I'd still like to know your opinion.