No hes on stright lpg with a heavily ported head and race cam.

Lpg does not like huge cams with its current mixer ring set up.
I was advised the 733a would be best by wade 72 maybe. The ported head I thought would be a potential issue with the signal the lpg convertor needed to create draw. Eg it needs some restriction in the inlet system to create the draw signal the convertor needs to meter in some gas - well thats what was I understood from lpg tuners I spoke to.

Id go stock head with more compression and either 733 ir 72 works cam max in the lpg setup.

How interested in injection are you? I'd go lpg injectors and an ECU, way easier to get it to do what you want with whatever cam. Since the gas is already there you probably just need the injectors, oxygen sensor and an ECU triggered off the tach/ coil.

LPG injection sounds good but will have to wait unfortunately. Does it operate in the same way as fuel?
I changed the camshaft in my sedan today with interesting result. I installed the 74 wade cam and its not a huge difference from what was in there, the car idles rough like the last cam and when driving the power comes on earlier and pulls longer. The power doesn't just drop off at 5000rpm. I will be interested to try out the wade 72 which I will try and get in this week just to see how it goes with the LPG.

Thanks for he link Dennis.

hey crumb you mention a wade 74 and 72 camshaft i cant seem to find it in there catalouge

is it a camshaft from this list?

http://www.wadecams.com/

Thanks!

Both my cars are L-series. I recommend giving them a call and having a chat they are really good at what they do.

ah right sorry i missed that it was a L series

Thanks!

Pretty much works the same, there's LPG vapour injectors connected to the vaporiser and a hose coming out the other end that clamps onto a barb in each intake runner. I think it's a bit crude but it works. I guess the vaporiser is set up as a pressure regulator. I'm sure any ECU could drive the injectors.

The pictures in this article http://www.autospeed.com.au/cms/A_110066/article.html look like what's under the bonnet of my car.

There is another option which wouldn't cost the earth. Whilst they are by no means 'the best thing since sliced bread' the impco mixers (either a 200 or 225, probably the former, though I note they do run the same airvalve assembly, so that 225 doesn't translate into weaker response/signal strength on a smallish motor (small by dino V8 standards of course!).

Their advantage is that they are an air valve mixer - you might say they are the lpg equivalent of an SU style carb. At idle/low flow, the airvalve drops downward and acts as a (slight, for that much flow demand) restriction - so that it will still get good signal strength and decent lpg metering at lower rpms.

THe complex convertor and amos ring style mixer - well the amos ring has no moving parts, and as such it acts a bit more like a fixed venturi petrol carb. Problem is that unlike a petrol carb, it doesn't have idle fuel slots underneath the throttle plates (which of course see high vac at idle, and allow idle fuel metering to work pretty darn well). The amos ring has no such equivalent, and the signal strength at low rpm (esp idle) is exceptionally low. you 'could' run a really restrictive amos ring, that would get idle and low throttle signal strength up but then of course it would be far too restrictive at higher flow/rpm/demand.

To get around that the amos ring setups have an extra 'circuit' in the convertor. And with the ignition on and the motor running, this circuit will be open (it is solenoid activated, and that activation is triggered by the lpg module. when you first turn the key on, it will engage for about 1-2 seconds, delivering some lpg. Then you start it and that lpg will ignite. Then as soon as the module detects a signal (more specifically a frequency - i.e. signals above a certain rate per second) - from the distributor, it'll re-initiate lpg flow, adn teh car starts and runs. This is a good safety item, because if the engine stalls (or you are in an accident) then the signal drops below the frequency and lpg stops flowing. Incidentally, if you have trouble hot starting with lpg and an amos ring setup, generally it is because it is flooded with lpg. Then the driver turns the key off and on, to restart, and it delivers another of those 2 second primer 'shots' flooding it more, and it gets near impossible to start. The trick there is either of the following - you can simply floor it, and keep cranking on the starter, not on and off and on and off, until it fires into life (may take a few seconds). Teh other option is you can switch the lpg/petrol switch (if it has one) to the middle or 'off' position, again floor the accelerator, and crank it over. WIth no new lpg being fed in it will clear up and fire into life in about 1/2 the time, all you need to do is be quick and as soon as it does fire, switch the switch back to lpg.

As mentioned the amos ring has little signal strength at idle. So you adjust that idle 'bleed' (it just keeps feeding it in, and you can of course adjust the rate of this bleed) - even with a modestly large cam you can adjust the idle to be ok. But the problem is that as you open the throttle, to just off idle, with the bigger cam, you have less vac, so it doesn't start 'generating' enough of a signal just off idle before the main lpg metering circuits start to take off). You can get around it 'a bit' with one option - adjust idle rpm, and idle mixture, now open the throttle a small amount, and it'll get to a point (as the idle bleed rate is not able to supply for the increased airflow that demands more lpg) - hold it at that rpm, and re-adjust the idle mixture. Often you can clear it up, and when you lift off the throttle and go back to idle, it'll still run ok. If that _is not_ the result, then you can look into what mixture setting is good for idle, what is good for just off idle, and then turn the idle mixture screw to a point halfway betweeen those two settings.

But ultimately it will only go so far (with regard to bigger and bigger cams) before it'll start to run so bad that any advantage of the cam in higher rpm ranges just won't make up for the poor running down lower.

So for all of those reasons, I'd really suggest running an impco 200 mixer and complex convertor. They aren't magical but they ought to give you better idle and just off idle performance without any loss of power as the rpms rise. With bigger engines, you can get to the point where the demand for lpg goes beyond the convertor's limits and it will start to ice up, but that doesn't happen till something like 320 bhp or so for an impco model E (or ohg x1, or aussie b2 etc, which are all functionally extremely similar) and you can also get beyond the flow capacity of the valve in the lpg tank (again at around the same mark, and even then it'd be only if you run at full rpm full throttle for extended periods, i.e. it wouldn't likely happen in a drag race).. But with engines more along this size, none of that stuff is a worry. In fact you wouldn't need a model E (though there is nothing wrong with using one) - an impco model L convertor will supply enough lpg without any problems (and can typically be scored from a wrecker fairly cheaply). A quick note - although the convertor can come from a variety of cars at the wreckers - possibly needing a seal/gasket kit put through them - the 200 mixers used on efi will all be 'feedback' moxers - with an air/gas valve that is deliberately a fair bit richer than is necessary, then, based on ego sensor, this mixture is 'trimmed' either via vacuum to the convertor lid to work against the vacuum/signal strength and lean it out to where it needs to be, or via a 'stepper' motor that is a restriction in the main lpg feed line) - anyhoo, if you get a 200 mixer for free, and it's a feedback one, you can replace teh air valve with one designed for non feedback/atmo/non efi setups. iirc teh 'wrong' mixer part number on the sticker on its side will include 'FB' (for feed back)

Thanks for all the info guys. It's a big help in find the right direction to head.