What combination?? --(Matt)

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

Hi,

I have a G161 in good condition and a G180 which has a burnt exhaust valve.
What would be the best combination for a rebuild???
For example...
1. 1600 block bored out, 1800 crank and 1600 head
2. 1800 block bored out, 1800 crank and 1600 head
3. 1600 block bored out, 1800 crank and 1800 head
4. 1800 block bored out, 1800 crank and 1800 head

The engine is being used in a 4wd, so torque is more important than all out power, so what do you guys recommend??

Thanks in advance.

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

As a wise man once said, theres no replacement for displacement, so I would go for #4.
You can put a real torquey cam in either motor, but because of more cubes, a G180 is likely to have more in stock trim.

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

I've heard you can bore the 1600 out to the 2L bore size of 87mm anyway. Meaning that you could obtain 2L from either setup.
Therefore, assuming that I can obtain 2L, which would be the better setup?

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

Hmm, I dont know. I've not heard that you could bore a 1.6 out to a 2litre, sounds a bit ambitious. The cylinder walls must be getting a bit on the thin side. One of the other guys can probably confirm or deny that, but assuming its correct, I would still probably go for the G180 as there will be less metal to take out, and since it is a larger size to begin with, possibly you will be left with thicker walls. I dunno, I'm only guessing now.
What do you reckon Adam? Anyone?

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

posted by Keith on Mon Jan 15 09:29:29 2001 from cache08.syd.optusnet.com.au
Here we go, as Keith posted yesterday:
1600 have a std bore of 82mm & stroke is 75mm.
1800 have a std bore of 84mm & stroke is 82mm.
2lt's have a std bore of 87mm & stoke is 82mm.

Therefore whoever told you that you could get 2 litres out of a 1600 must be wrong cause the stroke is 7mm longer. Maybe you could use the 1800 crank and the bore will support the extra 7mm, but I would be surprised if there is 5mm of spare metal in the cylinder wall.
But like I said, I'm only guessing...

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

The 1.8L/2L crank is required to get the 2L from the 1600. You just have to relieve/grind the block a bit to fit the crank in. 1600 rods are used and certain mazda pistons are used, which have a shorter distance between the gudgeon pin and piston face to account for the 10-15mm shorter block. So obviously it all comes down to the maximum size that a 1600 can be bored out to.
So does anyone know the maximum size a G161 can bored out to?? What about the G180 and G200 aswell??

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

Ok, using the 1600 block with an 1800 crank is to chase capacity that the 1800 block can give you with a lot less work, I would go the 1800 bottom end with the 1600 head, port the head lightly, but focus on the inlet side, if you get the exhaust flowing too well you may rob yourself of some torque, I hate trying to build engines for torque...

Go for 10:1 compression or maybe 9.6:1 if the 4WD is likely to be buying petrol from remote outback towns... Ask around a few different cam companies and see if any make a specifically torque oriented camshaft for the G-series motor. Play around with the ingition timing to try and gain low down torque (if I want torque I run 12degrees BTDC initial advance), if you feel like going to the extreme it is possible to play with the camshaft timing without having to either source or manufacture an expensive vernier pulley... ICQ #40093715

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

Thanks Ash and Adam, your info has been very helpful.

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

12 degrees! Is that on a G161? I'm running 6 but was getting a bit of detonation (I think I got some watered fuel), so went as low as 2 (very doughy off the line!) at one stage to try and stop it.
If you can go 12 OK then I'll give it a try...

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

12 degrees on a G180 bored to 2 litres with a G161 head, 30/70 cam, lightened flywheel, fully balanced bottom end, smoothed and polished combustion chamber(which helps reduce hotspots and therefore pre-detonation), moderately ported with polished exhaust ports and ported and matched inlet manifold.

It does however live on optimax, if I dared to run anything else I suspect I would find that it pinged itself to bits.

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

Just in answer to how far a 1600 can be bored out, they definitely dont take 2 litre pistons. I was bored one day and started playing around on my cylinder borer with a shoddy old 1600 and found that I hit waterjackets down cylinders 2 and 3 before I got big enough bores to fit them. Biggest I would recommend would be 1mm over 1800, or 85mm.

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

Adam,

How much power & torque do you think your engine is producing?

What times can you run down the quarter?

Are you using a gem carby?
Thanks,

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

I have no idea how much power or torque my motor makes, once I save enough money for twin 44mm IDFs then I'll get it dynoed and let all you ppl know first thing, but considering my continuing bankruptcy I wouldn't hold your breath.

No idea for 0-400m times sorry.

Yep stock carby due to monetary constraints, although I do have a 32/36 weber on the shelf with an adaptor, but it is an ugly piece of kit. The adaptor - as with most available - cuts off the secondary venturi almost completely, not worth the trouble and expense to tune.