Mechanical Terminology Questions

[Doob]

With regard to deck height and compression ratio .. I found this write up interesting - see link
https://daftenclassic.com/daften-classic...ck-and-set

[Oldman]

With regard to deck height and compression ratio .. I found this write up interesting - see link
https://daftenclassic.com/daften-classic...ck-and-set

Thanks Grant, that’s a really great article that links everything together with simple to follow examples.

[Grantus]

With regard to deck height and compression ratio .. I found this write up interesting - see link
https://daftenclassic.com/daften-classic...ck-and-set

That a great useful find. Thanks for sharing! 

[Oldman]

compression ratios have little to do with original specifications if modifying your engine
If you have a standard cam stay close to original specs
Any modified cam should list a ball park figure for cr
Bigger valve overlap usually means higher cr because of losses
smaller overlap means less cr. I've just finished a 1200 build with a STD cam and set the cr at 6.9:1 (original spec 6.5:1)
Runs nice and smooth. 
If you don't stick to these ideas overheating and detonation will plague your day.

As for deck height
Your cr needs to be as above but the distance between the piston and the flat part of your combustion chamber (squish area) is critical.
Enough gap so your piston doesn't touch the head when everything is Hot and parts (conrod, piston, crank) have expanded.
Close enough so air/fuel is not trapped in that area which will cause detonation (knock) when things are at running temps
1mm to 1.5mm but I favour 0.8 to 1.2mm (1.5 is too much)
Rule of thumb. The better squish, the better turbulence, the better combustion.
So if your cr is right but your deck height is too big, reduce your combustion chamber (flycut your heads)
if too small, open your combustion chambers (best around your inlet valves)

By the way good luck finding someone to do that ( who knows what they're doing, specially on the central coast)

Another by the way, I really hate the way the text box jumps around when typing in and hitting the space key.

Thanks Rick.....
It's all starting to make sense to me now.
(Haven't noticed anything jumping around when I type  ...but I'll keep an eye out for it.