Originally Posted By RAMM
Originally Posted By Crizila
Originally Posted By RAMM
That's all that I am saying. I increased through machine work-the compression ratio exactly 1 full point--these are the results. Make of them what you may. I offered my thoughts on why and how--I do not know for sure--I only know what I know and have observed. J.Rob
Sorry if my reply came off a little harsh, but your thread title leads one to believe that the HP gain could be attributed to a CR change alone, and my point was that that was not the case ( although stated poorly by me ). As stated in this thread, I think a quench change had partly to do with the improvement, and maybe piston top reshaping, etc. I to, appreciate all your hard work and sharing the results. Just wanna clarify to all that adding a point to your CR my not automatically have the same positive results as you did. Making multiple changes is my personnel nemesis, as I don't have easy access to a dyno - and 2 - 3 trips down the track once a month can give pretty limited info. beer


The piston tops were reshaped for the initial build. I did not do anything different other than decking the block .045" This was the ONLY change. Pistons were in the same configuration both times. J.Rob
Not how I read your OP - "CNC machined them with a slight conical dish". No matter, interesting post anyway. Regarding timing, had a similar experience when going from cast iron heads to aluminum heads. Timing requirements changed considerably. Wanted lots more. Besides changing the CR and in turn chamber design, could be material also ( cast iron to aluminum ). Think you were pretty much in the "sweet spot" as far as getting as much as you did with the CR change. I remember when the 426 max wedge motor first came out in 63. two versions - 11:1 and 13.5:1. In 64 they were only offering 12.5:1 on the high side. shruggy Diminishing returns?

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