I got a 1990 Sierra (or Sammy, as you guys call them).  I'm interested in overhauling the ignition system to get the best out of my LPG powered ride.  I'm also wondering if there's a HEI system available for a zook, and if anyone has installed one or gone this route.  If it's overkill i'd also like to be set straight.... I don't want to be spending $$$$ for 0.01% gains. 

My ignition is stock, 20 years old, and soon i'll have a fresh motor running a 105-110 octane fuel at a compression ratio of 10:1.

Suggestions please 

I looked up Pacific market, Sierra, SJ413 - there were no less than 43 different versions of the 1.3 Sierra  - any way - assuming your Sierra came from the factory with breakerless igntion - I'd say it's pretty good as it is.

Just so you get my drift - if you have no breaker points - you already have electronic ignition.

If I'm not mistaken - all of the Suzuki G13 variants came with breakerless ignition - certainly as far back as the 85 Samurais did.  Now if your LPG performance specialists explained more about why electronic ignition is a big advantage, you would have a better idea of what impact switching to a better ignition system would have.

Your thread over at auszookers shows an MSD igntion system - I believe a 6A, but I could be mistaken - the MSD boxes are capacitor discharge, and at low rpm, do a multiple spark (hence the name - Multiple Spark Discharge - that gives rise to the MSD brand name) - this multiple spark supposedly improves the low end performance with a lean mixture by virtually guaranteeing that one of the mutiple sparks will light off the lean mixture.  At high rpm they revert to a single spark.

The MSD boxes don't really allow you to fiddle with the advance curves - they are just an "ignition amplifier" that do as they are told by the distributor (either conventional points or transistorized like you probably have) or by the ECU - they essentially replace the ignitor that's in your distributor but with a couple of differences, in addition to the multiple sparks, instead of switching 12V through the coil, they charge a capacitor to a higher voltage (400V) , and then discharge that through the coil, giving you a "hotter" (higher voltage) spark.

Now - here's the thing - with a higher voltage spark, you can open the plug gap and still get a decent spark, that supposedly improves performance on a lean mixture - more combustible mixture between the plug gap, to ignite - but in reality, with good plugs, the stock G13 system works, and works well.

The  truth is I don't like capacitve discharge igntion systems - because of high failure rates on the capacitors.

So there you have it - the stock system is pretty good, and I dislike CDI ignition - now it's your money, it's your choice - I don't have LPG but I do have a high compression G13 running on gasolene, with the stock ignition system

Great Mr Fordem, thanks for the clarification.  I'll stick with the stock setup then.  

I just seem to have a ghost in the works and the only unturned stone is the ignition system - but apart from installing decent leads, replacing dizzy cap and rotor button i've left the ignition as is.  

My problem is a slight hesitation in acceleration, and an idle that is sometimes hood shaking, sometimes fine and other times after a long run it just stalls    It's not a vacuum breach on the intake side, the LPG system was also tuned a couple of weeks ago.  Grrrr    annoying!

I have ZERO experience with LPG (other than using it in the kitchen), and that's not likely to change any time soon.

Hesitation in acceleration on a carburetted engine is almost always a mixture related issue - a lean idle micture will cause it, and so will a failing accelerator pump (the diapragm tends to stiffen up with age, and reduce the amount of fuel that the pump delivers), if you're talking EFI, the TPS would be my guess - so - for LPG take a look at whatever mechanism provides that temporary enrichment.

Hood shaking idle - I would guess the RPMs are a little lower than they should be - easy to check if you have a tach - possible causes for a carburetted engine, the idle speed adjustement, and also the ignition timing - a shade tree mechanic's trick I learned in high school was to rotate the distributor for fastest, smoothest idle, and then adjust the idle speed using the carburetor throttle stop screw.  On a fuel injected engine - most likely the IAC motor - since that controls the amount of air - but we're back again to your fuel system and whatever controls the air & fuel at idle.

Same goes for stalling after a long run - I don't see that as being an ignition related issue.

It's possible that ignition timing is a part of your problem - see the hood shaking idle paragraph above - but that's not going to change when you add an HEI