Max Compression Ratio February 27, 2006, 12:30:55 PM I'm planning on rebuilding the SO 5.0 engine in my 87 tbird to the HO varity. Depending on which combination of parts the compression ratio can vary from 8.7 to 12.0. I want to continue using the 87 octane pump gas but while I'm asking I might as well ask for the other octanes.If you please would answer, What is the max compression ratio the 5.0 HO engine can take that won't cause pinging/detionation using the 87, 89, and 92 octane gasoline? Also does engine cubic inchs make a difference? Was considering stroking the engine. Quote Selected
Max Compression Ratio Reply #1 – February 27, 2006, 12:34:48 PM I'd say 10:1 is safe bet on 92 any more u can be pushin it... and altitude will have some bearing on it. dont think cubic inches gonna make much of ad ifference... u can get octane booster tho... and play with timing... but there is pro's and con's to playin with timing which i do not know but someone else will. Quote Selected
Max Compression Ratio Reply #2 – February 27, 2006, 01:18:10 PM Cubic inches only really matter in that the bigger the engine, the more power you can make on lower compression. I.e. a big block can make 400 hp on 9:1 easy, whereas with a small block that would be harder to do. Quote Selected
Max Compression Ratio Reply #3 – February 27, 2006, 06:50:39 PM I want to stay with 87 octane because this is a daily ride. Sure don't want to be adding octane boost. That would send me to the poor house. Quote Selected
Max Compression Ratio Reply #4 – February 27, 2006, 10:32:53 PM On 87, my guess would be that you probably wouldn't want to run more than about 9.5:1. Quote Selected
Max Compression Ratio Reply #5 – February 28, 2006, 03:51:40 PM 9.5 is good. Glad I found out before buying the wrong heads with smaller cc. Quote Selected
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