Thread: new top end and no more power???

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I went through the exercise of calculating your DCR for both straight up and 2* retard installation. straight up (intake close 41 ABDC) DCR=8.27:1... 2* retarded (intake close 43 ABDC) DCR=8.20:1. At 4500' altitude, barometric air pressure (at 68*F and 20% relative humidity) is 25.37inHg or 12.46psi (compared to 14.7psi at sea level). Given your DCR of 8.2:1 and 12.46psi your cranking compression should be 102psi... given whatever the prevailing weather was during your test, this could easily account for 2psi.

techinspector knows more about what a good DCR is than I do but I do know that 8.2:1 is pretty low if you want any kind of performance. I think 8.5-9.0:1 is a good target for pump gas friendly power. And at higher altitude you can push that a bit further... BTW: with the specs you gave here, my compression ratio calculator says you have 8.98:1 SCR.

Edit: I was using 64cc chamber... with 62cc chamber SCR is 9.16:1

Good luck...

-Chris