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working out compression ratios
#1
I'm posting this as found it difficult to find things in one place on the web. I wanted to know the exact CR on a Ricardo head machined for high lift cam [i.e. its got maximum volume possible] as I don't know the condition of the bottom end of this engine and whilst I want to use it as my LC head is quite badly corroded. I don't want to inflict big stresses on the engine. It's the first of the 1 5/16" crank and presently running with a Ruby manifold (ha!) which I will keep, with a 1" SU eventually.


I found that my pistons are +040, and the table in the back of the 750MC Companion gives 774cc.

That is thus 193.5cc per cylinder.

I have a little weedkiller millilitre dispenser and I filled 35, then 30ml, in order to pour into the compression chamber with a spark plug fitted.

1 cubic centimetre  = 1ml (seems impossible, but google says..)

I could get 30ml in, but unsure about the meniscus bit... so it may be a bit less.

193.5 divided by 30 gives 6.45 Compression Ration (29 would give 6.67) which seems just about ok if I use a standard gasket rather than a thin one.

I'd like to know where I can improve my maths and what else I haven't allowed for (or have done wrong) - will it be lower because of the gasket thickness for instance?
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Messages In This Thread
working out compression ratios - by JonE - 29-09-2018, 02:20 PM
RE: working out compression ratios - by Chris KC - 29-09-2018, 03:35 PM
RE: working out compression ratios - by JonE - 29-09-2018, 06:28 PM
RE: working out compression ratios - by jansens - 29-09-2018, 10:43 PM
RE: working out compression ratios - by jansens - 30-09-2018, 07:12 AM
RE: working out compression ratios - by JonE - 08-10-2018, 08:28 PM
RE: working out compression ratios - by jansens - 30-09-2018, 11:14 AM
RE: working out compression ratios - by JonE - 30-09-2018, 12:34 PM
RE: working out compression ratios - by jansens - 30-09-2018, 08:57 PM
RE: working out compression ratios - by JonE - 01-10-2018, 08:59 PM
RE: working out compression ratios - by GK5268 - 08-10-2018, 10:00 PM
RE: working out compression ratios - by JonE - 09-10-2018, 09:39 AM
RE: working out compression ratios - by JonE - 10-10-2018, 08:53 PM
RE: working out compression ratios - by JonE - 12-10-2018, 11:04 AM
RE: working out compression ratios - by JonE - 11-10-2018, 07:36 AM
RE: working out compression ratios - by jansens - 11-10-2018, 08:14 AM
RE: working out compression ratios - by JonE - 11-10-2018, 10:00 AM
RE: working out compression ratios - by jansens - 11-10-2018, 10:17 AM
RE: working out compression ratios - by Dave Mann - 11-10-2018, 10:23 AM
RE: working out compression ratios - by Dave Mann - 11-10-2018, 08:30 PM

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