Iron to Aluminum block/Burr finish to smooth

General engine tech -- Drag Racing to Circle Track

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Steve.k
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Re: Iron to Aluminum block/Burr finish to smooth

Post by Steve.k »

Frankshaft wrote: Wed Jul 11, 2018 7:22 pm I should add, iron Block rough finish left, aluminum block smooth finish right. Notice manifold vacc. Same pump, pulleys, etc etc, it UP vaccum. Also, notice the Engine on right has better more consistent bsfc's. This on Q. The aluminum Block/smooth finish wanted less jet to make MORE power, same carbs, cam, intake etc. The valve job was also untouched, seats were still nice. I did give the valves a quick clean up grind. I wanted everything to be as same as possible. That's one of MY expierences, so when I tell you that an aluminum Block doesn't lose power, it's not a theory. For those that lose power, I don't know what to tell you.

So, what is happening? Why does it want LESS fuel to make more power? I think the aggressive finish is peeling the fuel out if suspension, causing it to puddle. There for it needs more, to have enough that's atomized well enough to burn, to make that power. The smooth finish is not doing that, so it needs less to make more.
Frankshaft the smooth finish is interesting for sure. I have always polished the intakes and exh very smooth. On the exh side of two stroke snowmobiles always polish exh to mirror finishes. Always had gains. We only ever dynoed one sled engine but it had a pipe change also so hard to say what the separate gains are. I've done this to numerous sled engines with stock pipe and always went faster in 500ft drags.
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