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Old 01-28-2009, 08:31 PM
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How LOW compression ratio can be?

I'm working a set of vette heads to install on my SUPERCHARGED 350 SBC

the blower is a 144 B&M that pumps 8 psi with the current 882 head, I guess the high boost comes partially from the restrictive heads, it also has the smallest driven pulley that B&M had made for the smaller 305 engine.

it is a STREET engine and will burn pump gas

I want to extract as much power out of it and with the current heads I have to limit timing a lot because it pings like crazy so actually does not make much power.

I've seen racing turbo engines with compression ratios as low as 5.5:1 but they are racing engines, what would happen if I go that low on a street engine? will it be a real dog when there is little or no boost?

I used to have a '62 Land Rover that had 7.1:1 compression ratio and was a very smooth and torquey engine.

My plans are carving the heads a lot unshrouding the valves, this will let them breathe very well and will reduce compression at the same time.

please give me your opinions, thanks.

Augusto.

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Old 01-28-2009, 08:53 PM
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Eight pounds of boost isn't excessive, combined with a cr of 8:1 you're fine with pump gas.
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Old 01-28-2009, 09:09 PM
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but pings like crazy and I have to run very low ignition timing to compensate, our gasoline is not that good, I should of say this first, I was thinking of installing water injection but I think I will be better with a lower compression that will allow me to pump more air into the cylinders and make more power, in other words make the engine think it's bigger.

Augusto.
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