G200 oversize pistons and capacity

sinads1 · rice boy Joined: 31 Dec 2003 Posts: 11

Can anybody tell me what the resulting engine cubic capacity is with each of the oversize pistons
Eg:
Std = 1949cc
10 thou over = ??
20 thou over = ??
etc etc

Cheers

sinads1 · rice boy Joined: 31 Dec 2003 Posts: 11

Sorry - I was speaking old language!!!!

Std = 1949cc
1mm thou over = ??

etc etc

GasGem · backyard mechanic Joined: 05 Nov 2001 Posts: 755

from a previous post by someone else...

g161z has 82mm bore and 75mm stroke.
g180z has 84mm bore and 82mm stroke.
g200z has 87mm bore and 82mm stroke.
g161z capacity is actually 1548cc
g180z capacity is around 1850cc
g200z capacity is around 1950cc
The maximum overbore ive ever seen in a 2litre is 60thou or 1.5mm. Someone may know of a bigger one but i doubt it cos there is barely enough cylinder wall to seal when its bored 60thou over. Working with the rough size that the difference between a g180 and a g200 bore size is 3mm and that gives 100cc, a 1.5mm overbore should give you and extra 50cc correct? Therefore the largest possible non stroked g200 capacity will be 2000cc exactly. So why do people talk about boring motors to 2.3litres? And if i fit 2litre pistons to a 1600, I barely get 1750cc. And while im sure it is possible, I am yet to see or have proven to me that stroking a gemini motor is possible. People talk about hilux cranks and corona cranks, none of which come close to having the right journal spacing to fit a gemini. So unless you know things I dont, and I know alot of engine reconditioners in queensland, I would pretty much rule out stroking a g180z or g200z.

sinads1 · rice boy Joined: 31 Dec 2003 Posts: 11

g180z capacity is 1817cc
g200z capacity is 1949cc

with the same stroke.

The difference is 3mm in bore size ie 3mm = 132cc

therefore 1mm = extra 44cc
therefore 1948cc motor (2litre) overbored 1mm = 1993

Correct(ish)???????

Cheers

QldRobbo · tinkerer Joined: 11 Apr 2002 Posts: 455

Yep, it actually is 1993.93cc, so 1994cc.. I wouldn't recommend doing this to an engine personally for two reasons

1) you won't be able to tell the difference performance (or any other) wise
2) If you take a block and bore it out to it's max it means when you next need to rebuild that engine you will have to get the bores sleeved because there isn't enough wall left to take out any nicks in the metal...

sinads1 · rice boy Joined: 31 Dec 2003 Posts: 11

The block has already been bored 1mm so = 1993

When you fill the bore with fluid to measure the fluid capacity it has it measures 560ml for each bore(2240 total)

the head has 44ml capacity

what I am trying to figure out is how much needs to be taken out of the combustion chamber to have a compression ratio of 9.5 to 1????

is there a formula to conver ml to cc ??

Cheers

ATG23Q · tinkerer Joined: 10 Aug 2003 Posts: 201

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

1 millilitre equals 1 cubic centimetre.

1ml = 1cc

Do you mean 560 with the head fitted, filling through the spark plug hole? Either way, filling with fluid is not the best way to measure as the fluid can leak past the piston rings, maybe this is why you measured 560ml and should have measured a bit less than 500ml per cylinder.

Therefore, your current static compression ratio is (cylinder volume + head gasket volume + combustion chamber volum)/(head gasket volume + combustion chamber volum).

a 1mm bored G200 will have a bore diameter of 88mm. the stroke is 82mm. Therfore, the volume of a cylinder is the area by the length. = pi x radius^2 x length (easiest in centimetres)
= 3.1416 x 4.4^2 x 8.2 = 498.73cc

The average head gasket is 1mm thick, therefore is about 6cc in volume.

if you have a 44ml combustion chamber volume, then it is quite a small 1600 head, and will have pretty high compression already.

static compression = (498.73+6+44)/(6+44)= 10.97:1

thats pretty high, and you will have to make the chamber bigger, use a bigger chamer (ie G200 head) or dish the pistons to get back to 9.5:1.

You would need a 52-53cc head to achieve that.

Ben

Poida

Have a look in the 'engines section at 'workshop'.

Keep in mind metric engines are measured in mm not inches, always!! No point speaking in thousandths of inches when they don't make them in inches to begin with.

It's like going to the USA and trying to convert things from miles to kilometres then back again as they don't understand metric there like we do. Pointless exersize!

I previously corrected a post on the capacity of G series engines...
These capacities are close enough to correct unless you need the exact figure. i rounded to the nearest mm.

G161Z - 82mm bore and 75mm stroke. (1584cc)
1604cc @ 0.5mm O/S
1623cc @ 1.0mm O/S
1643cc @ 1.5mm O/S
G180Z/G180W - 84mm bore and 82mm stroke. (1817cc)
1839cc @ 0.5mm O/S
1861cc @ 1.0mm O/S
1883cc @ 1.5mm O/S
G200Z/G200W has 87mm bore and 82mm stroke. (1949cc)
1972cc @ 0.5mm O/S
1995cc @ 1.0mm O/S
2018cc @ 1.5mm O/S

It may be possible to bore to a greater limit than the 1.5mm shown although you won't get off the shelf pistons for say 2.0mm o/s as they are not made. It could be possible to find a piston made for a different engine type that will fit. I don't really understand why someone would want to go to the extent of such an exersize for all the problems it creates.
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sinads1 · rice boy Joined: 31 Dec 2003 Posts: 11

Cheers

Simon N