BillGrissom
Well-Known Member
Below are photos of two harmonic balancers. The left was on a '65 standard 273 (2 barrel carb, flat-top pistons) and the right on a '65 Hi-Po 273 (4 barrel carb, raised pistons).
One difference is the std one has casting label "S-2" and Hi-Po has "S-5". Interestingly, the "S-5" is "upside-down". No, I am not reading it wrong, but perhaps a foundry worker did in dim light. I don't find anything in a search, and don't know if these are PN's. "M-E" may be the foundry.
Another difference is the Hi-Po has two drilled holes. I assume these were for balancing. I have seen similar drilled holes in other balancers (my Newport 383 I think), but usually radial. Why? Aren't all '65 engines internally balanced? I read that Hi-Po's have lighter piston pins, but I recall the pistons were heavier. Anyway, should that matter if all pistons assemblies are the same weight. Is a Hi-Po crank different? More likely, they spin balanced the final assembly, drilling the balancer as needed. If so, it should stay with the engine.
Several people have claimed the only way to know that a 273 is a Hi-Po is to pull a head and look at the pistons. If the harmonic balancers are a different PN, this could be another way, though the labels are on the backside and "S-5" can look like "S-2" without a good cleaning.
I was preparing to use the Hi-Po harmonic balancer on my standard 273 because the later one has a stripped thread. But I caught myself, after many mistakes not considering when something matters - model/year, left or right, different ways something can mount. Fortunately, the stripped hole marked the balancer so I didn't mix up which came from which engine. I will fix the thread and re-use.
BTW, someone might wonder why I am not using the Hi-Po engine. First it isn't installed and was seized from dirt and wet leaves. I got the pistons out, but chipped the bottom of some doing so. Not sure the cylinders will hone to std bore. Long term project. I'll be real happy to just start driving the Dart as built. Everyone pesters me, "when are you going to get that car out of the garage?" I answer, "how many cars have you rebuilt in the last decade?" (dumb tourists).
One difference is the std one has casting label "S-2" and Hi-Po has "S-5". Interestingly, the "S-5" is "upside-down". No, I am not reading it wrong, but perhaps a foundry worker did in dim light. I don't find anything in a search, and don't know if these are PN's. "M-E" may be the foundry.
Another difference is the Hi-Po has two drilled holes. I assume these were for balancing. I have seen similar drilled holes in other balancers (my Newport 383 I think), but usually radial. Why? Aren't all '65 engines internally balanced? I read that Hi-Po's have lighter piston pins, but I recall the pistons were heavier. Anyway, should that matter if all pistons assemblies are the same weight. Is a Hi-Po crank different? More likely, they spin balanced the final assembly, drilling the balancer as needed. If so, it should stay with the engine.
Several people have claimed the only way to know that a 273 is a Hi-Po is to pull a head and look at the pistons. If the harmonic balancers are a different PN, this could be another way, though the labels are on the backside and "S-5" can look like "S-2" without a good cleaning.
I was preparing to use the Hi-Po harmonic balancer on my standard 273 because the later one has a stripped thread. But I caught myself, after many mistakes not considering when something matters - model/year, left or right, different ways something can mount. Fortunately, the stripped hole marked the balancer so I didn't mix up which came from which engine. I will fix the thread and re-use.
BTW, someone might wonder why I am not using the Hi-Po engine. First it isn't installed and was seized from dirt and wet leaves. I got the pistons out, but chipped the bottom of some doing so. Not sure the cylinders will hone to std bore. Long term project. I'll be real happy to just start driving the Dart as built. Everyone pesters me, "when are you going to get that car out of the garage?" I answer, "how many cars have you rebuilt in the last decade?" (dumb tourists).
