19 replies to this topic

[Bluemini]

So what would a 23cc chamber make the c/r then?

[Turbo Phil]

9.48-1 with 23cc chambers.

[Boab]

Okay Phil, what does all the above mean, and how do you measure the 'cc' that you mention.

I can see from the pic in Bluemini's thread that a chunk has been taken away from the valve chambers, what advantages does this have.

Logic on my behalf says it makes each cylinder slightly larger, ie 73.5mm=74mm, if you get my drift or am I waffling.

What is 'swept volume'?

What do you measure to get block height?

Cheers

Anyone

[Turbo Phil]

Sorry ! :grin:

To work out the compression you need to know several factors.
1. - The swept volume of one cylinder {V}. To do this you divide the number of cylinders by the number of cc of the engine. In this case 1312cc divided by 4 = 328cc.

2. - The total volume above the piston {C}. In this case -
Pistons = 10cc {dished}
Head gasket = 2.8cc {BK450 Gasket}
Head chambers = 25cc {for example}
Piston to block height = 2.04cc {If the piston sat 20thou down at TDC}Measured using a DTI gauge {calculations in Vizards book}
Volume contained above the top ring = 0.80 {estimate,guided by Vizards book}
This all adds up to 40.64cc.

{V}+{C} divided by {C} gives your your compression ratio.

Hope this helps.

[Boab]

Almost understood Phil, thx. Need to get a Vizards book I think