LM7 with 4.8 pistons
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Teching In
Joined: Jul 2019
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LM7 with 4.8 pistons Hi everybody.
i've searched high and low but cant get a straight answer. How much HP can I expect from changing an LM7 (5.3) pistons to flat top pistons. This will raise the compression up to 10.4:1 but how much HP does that equate to?
I'm on a budget and only have money left for a cam. I've ported the 706 heads myself.
i've searched high and low but cant get a straight answer. How much HP can I expect from changing an LM7 (5.3) pistons to flat top pistons. This will raise the compression up to 10.4:1 but how much HP does that equate to?
I'm on a budget and only have money left for a cam. I've ported the 706 heads myself.
Probably not even half that. It's usually a 1.5% to 3% increase in HP for 1 full point of compression so if it made 300hp before the new number would be a 4.5 to 9hp increase.
Calculate New HP From Change In Compression Ratios
Calculate New HP From Change In Compression Ratios
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TECH Fanatic
Joined: Dec 2019
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Probably not even half that. It's usually a 1.5% to 3% increase in HP for 1 full point of compression so if it made 300hp before the new number would be a 4.5 to 9hp increase.
Calculate New HP From Change In Compression Ratios
Calculate New HP From Change In Compression Ratios
Despite the 317s flowing better, the difference is about 15 HP.
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Yeah, In that case it's not doing the math correctly and even if it didn't it probably would still read low because it would fail to account for the added power of going to the better fuel that would be needed at that ratio. I've never tested a compression increase myself where nothing else was changed but plenty others have so it not like it hasn't been proven. A 1%-3% increase for a point of compression is typical if that's the only change . I had someone tell me their sbc went from 275hp to 450hp because they went from 9:1 to 11:1 but to get from 9 to 11 he went from crappy cast iron small valve heads to Brodix Track 1's and new pistons.