15:1 static compression

Adam · Site Admin Joined: 04 Oct 2001 Posts: 682

For those that don't know, I am about to screw together a G200 for Gerty... It just occurred to me... the G200 almost has a zero deck height and flat top pistons... The G161 early model head I've got has been machined a fair way... I haven't CCed the combustion chambers yet, but I just realised I'm probably going to end up with 15:1 static compression... I guess I'll just disconnect the spark plug leads and run her on diesel then. Razz

No biggy, I can arrange a thicker headgasket and I was going to machine the combustion chamber a bit anyway... Just thought I'd post about it...

TXcoupe · petrol head Joined: 05 Oct 2001 Posts: 1675

or just run it on methanol

Slug · tinkerer Joined: 06 Oct 2001 Posts: 196

I have never heard of a gemini comp ratio that high with standard bits ? I will be interested in knowing what you end up with once you CC the head .. dont forget to CC the head gasket as well .. Michael

Ben Wight · backyard mechanic Joined: 04 Oct 2001 Posts: 946

I'd say you would the most you could get would be about 13:1 with 35cc chambers, which are tiny. I would say more like 12:1 adam, with a heavily machined big valve head. My TD head was machined nearly to the valve seats and had 40cc chambers.

Ben

Eggy1 · newbie Joined: 04 Mar 2002 Posts: 6

have you considered O'rings to keep that kind of comp in?
sound fun thou,

Cheers
Eggy

Mark · tinkerer Joined: 04 Oct 2001 Posts: 153

Ive had heads that are almost machined down to the valve seats as well, and you cant get more than about 11.7:1 with standard bits. I needed lumpy top pistons to get 12.75:1 comp in one motor i built.

Adam · Site Admin Joined: 04 Oct 2001 Posts: 682

Oh well, I had another look at the head at the combustion chambers aren't as small as I remembered, so I'll probably only end up with 10.5:1, which is about exactly what I want!