As I was going through this process at the weekend, I thought I'd take a few pictures, I know a lot of you will be familiar with this, but hopefully for those who have not seen this before it will be of assistance

Firstly I made a plate from a free offcut of 4mm perspex, then drilled a 3mm hole:

This is how it will fit and seal the head:

Seal the face with a little grease:

Then run in liquid (I used kero) from the burette to measure ther volume:

This being a 12G295 head, I added 5ml (CC) to start with, then measured:

So 5 plus 22ml is a total of 27.0 ml for this head which has had a clean up skim (12G295 usually 28.3 ish..)
Final picture of full set up:

Burettes are available from Lab supply places.
I also did the same excersise on the block with the piston at tdc, the dished piston and area above the piston yielded 9.5ml, so total volume on this 0.060" over 1098 is 36.5ml, plus say 1.7ml for gasket (tot 38.2)...

So, question time! what's the current compression ratio!

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Sir Alec! we are not worthy!

CR = total combusted volume(CV) + the swept volume (SV),,, divided by the swept volume (SV)

or,,, CV divided by SV +1

so,,, "IF" your head gasket holds 1.7ccs (i`d say it will be more like 2.5mm actually but you should measure it) & if you have actually got 38.2ccs total

then 1098 + .060 oversize is 1150cc

divide by 4 for one cyl = 287.5cc

ok,, so our CV is supposed to be 38.2 divided into our SV which is 287.5,,,which then = 7.526..... Plus our "1" which then = 8.526 -ish

but i`d guess that your head gasket holds more than 1.7cc so i`d say thet you comp ratio is actually slightly less than 8.5:1

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

translated *blah blah blah... comp ratio 8.5:1 GET A TURBO ON THAT!!!

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Here am I sitting in my tin can far above the Moon
Planet Earth is blue and there's nothing I can do...



“A turbo: exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster.” - Jeremy Clarkson