Dyno Testing A Home-Built Pontiac Motor - Backyard-Built Bruiser
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Here you can see quite a bit of SD's handiwork. Note how the chamber is now a heart shape to promote swirl, improve combustion and ward off detonation. According to SD Performance, the efficiency of the chamber allows for 2-degrees less timing. The valves are large 2.19 intakes with 1.77 exhausts. Cygan says, "The intake valve is actually big for this combo and is shrouded more with the 4.190 bore than we would like to see, but we did it because we may run an IA II block in the future. This way we don't have to redo the heads." Chamber size has also been reduced to 64 ccs to increase compression. Dave related that regardless of any shrouding, the big intake valve will still make more power, even with the relatively small bore, than the 2.11-inch intake. View Related Article
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