Compression Ratios?
11-22-2002, 07:22 AM
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Compression Ratios?
What is the best compression ratio to have in a 454NA carb motor for max performance and no detonation when using 89 octane fuel?
11-22-2002, 07:43 AM
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Depends on heads, cam, ignition timing, plugs....generally
9.25 Iron is about it
9.75 Aluminum
If you want to run 93 Octane I would say...
9.5 Iron
10.5 Aluminum...I have a NA 632 Carb motor running here with no detonation probs.
9.25 Iron is about it
9.75 Aluminum
If you want to run 93 Octane I would say...
9.5 Iron
10.5 Aluminum...I have a NA 632 Carb motor running here with no detonation probs.
11-22-2002, 07:44 AM
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For 89 octane 8.5 to 9.0 for iron heads and a max of 9.5 for aluminum heads. Running 93 octane will allow you to add .5 to the 89 octane numbers. Cam selection also has a bearing on how much comp can be tolerated by pump gas. I know guys running 10.5 on 93 octane and aluminum heads with no problem.
11-22-2002, 03:19 PM
#6
I wouldnt go over 9-1 with iron heads. That way you can run your ignition timing around 34-36 without worries. Keep in mind that cam selection is dependant on many things including compression ratio and exhaust used.
11-23-2002, 05:56 AM
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Dyno and SuperV are both running 9.6:1 with iron Merlin heads on 89 octane fuel. Dyno's been running for two seasons and SuperV just completed his first season on these engines with no problems whatsoever. Timing on both boats is 32 degrees total advance.
