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Hi Eric. If yu don't use 100 octane or thereabouts for fuel, it's not a power question but a detonation question. With the small chamber volume of the Ram Air lll heads, you will be close to 11:1 compression. Great stuff back in the day, but your engine will detonate itself to death (ping). The dished pistons will make your combustion chambers larger in effect, lowering your compression to the 9:1 range or so....maybe 9.5:1. You won't put out as much power as an 11:1 engine with all else being equal, but you will be able to drive the car on the street on pump gas. You could go with the Edelbrock or KRE aluminum heads....they will net you about 10.5-11.5 to 1 compression, and will work on the street without problems because they are aluminum and dissipate heat much better (no detonation). However, because the thermal efficiency of aluminum is inferior to iron, they need meore compression to make the same power as iron heads. If your car is mainly a street driven car, I'd recommend the dished pistons. If you want to save a lot of labor, you can do what I did and get a pair of later heads that still flow well, but have bigger chambers: 85--100cc. I put a set of 1970 455 #15's on my '67, and they have an 87cc chamber. Compression is about 9.2:1, it doesn't ping, and power is good. It did have more power with the 670 heads on it, but it was pinging ALL the time. Hope this helps.
Jeff
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