When the Eddys first came out, I bought a set for my 500" stroker project. At the time, I had a very worn 440 in the Cuda that only had a cam, intake/carb swap and headers. At the end of the driving season, I decided to throw the Eddys on the engine just to see what they would do. Some said that the car would actually slow down due to the low compression. To be honest, I don't know what the ratio was.
Anyway, with no other changes, from one weekend to the next, the car picked up nearly a full 2 tenths with just the head swap. That was obviously due to the better flow of the Eddys over the stock iron heads, but if the aluminum hurt anything in this case, it was not much nor noticeable.
Just my experience.
My experience has pretty much been the same. I went from stock iron 452s to Edelbrock E Streets and picked up nearly two full tenths in the 1/8 mile. I think there's more in it too because on my one run since swapping, the car was sputtering and then lost all power in the top end due to a loose alternator stud shorting out.
It also seems to be idling and running smoother and getting better gas mileage since swapping to the aluminum heads. I wish I would've just built my 440 with the aluminum heads to begin with.
