Hi all from Australia, and another zook lover.


I'm hoping you guys can help me out, I'm a member on a few local Aussie 4x4 forums but nobody can really give me solid advice as to my plans.

I'm going to rebuild my G13A from my 1990 Sierra.  Firstly, I'm trying to find out the duration/lift specs of the stock camshaft - just so I can compare the replacement options available with the current install.

Secondly - i'm rebuilding the motor to run straight LPG, I'm wondering what specific tweaks I can deploy to get the best out of the fuel... I'm the only zooker in Australia running LPG that I know of, so advice is very thin on the ground.

My 2 cents worth (US),

My experience with straight LPG engines is from the Farm Industry.
Minneapolis-Moline built factory LPG engine Tractors, the heads on these engines had a way Higher compression ratio (Smaller Combustion Dome) to get the max horse power/hour from the High BTU LPG.
I don't remember a different cam set up.
I still have a "Dual Fuel" Waukesha (Gasoline/LPG) 15 KW gen-set from the mid fifties for when the power gets knocked out here in BFE.
To run on LPG, you start it on gasoline and get it warmed up, then switch over to LPG. It's just hard to start on straight LPG.
I think this is it probably had the stock compression ratio of a gasoline engine.

Hope it gives you a little insight.
CAPT

Propane is a high octane fuel, so a set of flat top pistons would
be worth the investment, I don't know how high of compression
ratio you can get, but 10:1 would be good, you could also go the
other direction and get a low compression set and do a turbo setup
on that engine, propane is excellent turbo food too.

As far as cams, you want to take care as to not upset the lower end
torque but perk it up a bit, a little more lift and duration over stock
worked well for my engine and I suspect it would be fine for you too.

Is this an 8 valve engine or a 16 valve ?

Wild

I've got an 8v 1.3 - been running straight LPG for a year now (no gasoline tank at all), but the motor I installed it on already had 140K miles. I'm up to 160K on the clock now after a few big tours, and chewing through enough oil to let me know I gotta rebuild or replace the motor pretty soon.  On my last trip I went through 16 litres in 6500 kilometres... I think that's 4 gallons in 4000 miles 

FYI - propane isn't available to the public over here, it's an industrial fuel only... sadly we can't run forklift bottles, tanks have to be hard mounted    Propane is 110 octane I believe, whereas Aussie LPG is around 105.

I'm looking at a 10:1 compression, but yeah, as far as I know a rebuild starts with the cam - not sure if I have to adjust the cam specs to suit.

No, the LPG will work fine with the stock cam, but when you have
a high octane fuel you can push the normal limits with a cam and a
compression increase, 105 will work well with 10:1

Wild

OK, so I should hunt for cams with a low end boost than those offering top end power... like the 260 Torquer that LROR sell:

http://www.lowrangeoffroad.com/index.php/suzuki/samurai/engine-upgrade/hawk-1-3l-new-billet-replacement-cams.html

The specs on that site don't offer much information, just a number
but is it lift or duration??? I think either of those cams would work
OK, I mean torque on a 1.3L engine at 1000 RPM? It's not a normal
operating range for that engine, they idle at about 800, I think you
would like the higher end RPM cam, that's where these little engines
do their best work. You are going with a high performance fuel, let
the engine work and take advantage of the compression and RPM

Wild