29-09-2018, 02:20 PM
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?
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?