[Che]

I thought i'd make one topic of this rather than 50 posts as I plod along with my upcoming rebuild.

I'm supposed to be looking for a job, but sorting out an engine rebuild is far more interesting


The basics: I'm gonna rebuild a 1.3L for my Sierra, and it's gonna run straight LPG. I want a motor that is extremely reliable, low maintenance and cheap to run. A few extra horses would be nice, but I don't want to change the intake or exhaust at all, and apart from a few tweaks to optimise combustion for LPG I want to keep things as stock as possible.

Please - no suggestions to change to a 1.6 or EFI, it's not gonna happen.



Anyway - a bit of web based research and it seems like an 11:1 compression ratio is pretty reasonable for a straight LPG zook engine... how do you match a camshaft to this compression? Or am I supposed to do it the other way around and match compression to a camshaft?

[royce]

compression to camshaft and fuel

keep in mind the work needed to support such compression, youll need special work done to teh head and block (O ringing) as well as a special headgasket to work with it, this will cost a fair bit

I would be inclined to keep it down near 10:1

[Mistaria81]

well, u really don't have much options for more power if u want it stock, maybe a larger camshaft perhaps. if not talk to a mechanic that specialise in zook and or lpg engines. I know you can do a lot of hp mods with lpg but you are still gonna be restricted for power by keeping it stock. GL with the build, will be interested how it goes

[Che]

FYI - I don't really need any extra power. I got no plans to run 31's and I can do 110kph with a fully loaded car... thats good enough for me, a few more horses would be icing on the cake though.

That said, i've been eyeing off the Torquer 260 camshaft from LROR. I don't think i've ever revved it out past 5000RPM, so this would be the cam for me... more pep in the range that I use.

Can I get away with a standard reconditioned head using a camshaft like this, or am I gonna have to tweak the springs and rockers?

[royce]

you have to do the rockers no matter what, they are reground so they can bed in with the new cam, if you dont things will wear all strange

talk to Tighe cams in Brisbane, they can do it all for you

[alien]

wouldnt a weber carby shine using LPG? leaving the engine pretty much standard (ie cheap) and throwing on something thats easy to tinker with and puts in more air and more fuel? (well, as much as as it can on a 1.3).

[slyvan1]

make sure to get distributor re-curved. gas requires different timing

[royce]

alien wrote:

wouldnt a weber carby shine using LPG? leaving the engine pretty much standard (ie cheap) and throwing on something thats easy to tinker with and puts in more air and more fuel? (well, as much as as it can on a 1.3).

No, go learn how LPG works

a dedicated gas carb might be (an overly expensive) option though

[alien]

fair enough, yeah i read up on it but still dont fully understand the witchcraft of lpg =S (been a long day).

i did however learn that the toyota R series motors had LPG variants built from the factory... and the 7R out of a 1969-1971 corona 1.6 had an LPG variant, as did the 12R (also a 1.6) which ran in the corona and hiace from 1969 thru 1983... is this not a way of getting a dedicated gas carby cheap???

[Che]

Any carby on an LPG engine is only a throttle body as you don't use the fuel jets, it's basically just a throttle butterfly to control fuel feed. Rather than upgrade the carby you'd want to get a bigger regulator and higher flow mixer ring for greater fuel feed rates, thus more punch.

I think you'd find if you A/B my setup with a petrol equivalent you'd realise mine already has a waaay better kick than your regular 1.3... when the setup was in better health I could sit on 120kph with a stock exhaust no worries from brissy to the gc. It's enough for me, that's why EFI or a 1.6 is off the menu.


I'd love to piss the Aisin carb off though, not the ideal carb for LPG. Something single barrel is the ticket... but that's a problem to solve in 100 pay days.


As for timing... that's another concern. I'm yet to ask if re-curving a dizzy is the answer or maybe an electronic ignition system... I really noticed the timing issue travelling from east to west.

[Teracis]

che_guitarra wrote:

Any carby on an LPG engine is only a throttle body as you don't use the fuel jets, it's basically just a throttle butterfly to control fuel feed. Rather than upgrade the carby you'd want to get a bigger regulator and higher flow mixer ring for greater fuel feed rates, thus more punch.

I think you'd find if you A/B my setup with a petrol equivalent you'd realise mine already has a waaay better kick than your regular 1.3... when the setup was in better health I could sit on 120kph with a stock exhaust no worries from brissy to the gc. It's enough for me, that's why EFI or a 1.6 is off the menu.


I'd love to piss the Aisin carb off though, not the ideal carb for LPG. Something single barrel is the ticket... but that's a problem to solve in 100 pay days.


As for timing... that's another concern. I'm yet to ask if re-curving a dizzy is the answer or maybe an electronic ignition system... I really noticed the timing issue travelling from east to west.

If that's the case, what about getting a throttle body instead? I don't know s.f.a. about the whole deal just suggesting if you're using the carby as a plain old butterfly valve, why not use a proper throttle body (unless they are expensive?)

Also, how much trouble was it to convert to gas? You say it goes way better, why do we not have more lpg zooks?

[alien]

Teracis wrote:

why do we not have more lpg zooks?

because of the huge size of an LPG tank.

[royce]

air feed, it controls the air feed into teh engine

x2 on the throttle body, youll need to get one that will have a suitable vacuum advance port though

[Teracis]

royce wrote:

air feed, it controls the air feed into teh engine

x2 on the throttle body, youll need to get one that will have a suitable vacuum advance port though

WOO I came up with a useful suggestion!


Also as to what alien said, Is it required to be one big tank? or is it allowable to have twin smaller tanks? I'm guessing one big tank otherwise everyone would be hiding tanks everywhere?

[Che]

Teracis wrote:

Also, how much trouble was it to convert to gas? You say it goes way better, why do we not have more lpg zooks?

It's a leap of faith kinda thing I guess, LPG is an unknown to most, and there's bugger all online in regards to LPG performance.

It cost me $600 I think after the govt rebate, but I had problems where my petrol tank had muck in it, fuel pump was ratted and the carb jets needed a clean... it was cheaper just to go LPG.

[2stroker]

I would love to see dyno figures on your car, I have been mates with Des Eagan from Cabgas for 15 years, I have spent many evenings watching him fit and tune gas conversions, I have also had a lpg 4x4 and i don't know of any that improved performance over running petrol like you have achieved. I will explain why when I am not trying to type on a phone.

[Che]

I actually would too. I think I gotta get on a dyno it to get a dizzy recurved don't I? I don't understand how they'd map the timing under load etc otherwise.

I copied this kit from Got Propane, listed for zooks about halfway down the page. I've gone for a slightly smaller system so economy is better. Albion Metrogas did let me try the exact same setup but it ran like a pig as I didn't have decent exhaust or K&N at the time. Not trying to say my engine is a fireball, but the conversion definitely gave me gains, no loses by any measure.

Keep in mind i'm running straight LPG, not dual fuel. Running straight you can tune an engine perfectly, dual fuel you have to tune for an average best which always means a performance compromise.

[royce]

You might be running straight but youve not changed anything that would be common ground between both systems, IE timing, exhaust, engine internals etc

[slyvan1]

i do lpg conversions as part of my job. Some cars perform really well on lpg, and others are poor.

When i first converted mine before the turbo, it ran alot smoother, just running the mixer ring on top of the carbie. That being said the carbie history and condition was un-known. It would be hard to say if it gained or lost power never dyno'ed. but alot nicer to drive.

Because lpg has a different burn point to petrol, that is why re curving the distributor benefits performance plus economy. lpg requires more initial timing but then less total.

Tank mounting is a problem under a sierra because of the narrow chassis, can be done but it's only a small tank, in my lwb it's behind seat in front of wheel arch its 1200 long 360diameter, which is around 100 litres usable

you can fit more than one tank, just gets expensive with all the legal hardware to run more than one tank and it's time consuming.

[Che]

The only thing I did was advance the timing 3 degrees - got that done straight after the install. But, I've since got a K&N filter, a decent 2" exhaust - now time to rebuild the lump of metal in between, starting with the cam.

Does anyone know what the camshaft lift and duration specs are on a carby 1.3 cam? I've found a few replacement options from Camtech, LROR, and Isky, i'd like to compare their differences with the stock cam.

[Che]

Cylinder 3, we have a problem. Spark plug should not look like this after 7000K's.

[alien]

that would explain the soot coming out the exhaust then =)

[smiffkid]

i believe he quoted last night, that he now wants a 1,6 and 31s, he was very impressed with your zook aron,

[alien]

31's arent exactly ideal for a 6000km drive though =)

[smiffkid]

yea if u have gearing and all, will be alright, u get used to it pretty quickly

[Che]

Ha ha, Alien's zook is a beast, it definitely leaves mine in the dust on the road and in the dirt... but back to reality - a sorted 1.3 and 235's is where i'll go, and what I can afford. That'll still be fun out on the tracks and suit my daily drives and touring missions.

Power is waay down on where it was 6 months ago, especially after my Nullarbor mission, if I can get that back plus 10% it's a win. I'm living on my credit card so major upgrades are off the menu for now.

[mondo]

if you need anything like a good block or head for this, in case your's needs any work, i've got 1 of each sitting here. both were in very good condition. dunno if its worth the postage though to send such a thing

[Che]

Good one Mondo, I should be right mate, but thanks for the offer

[Che]

OK, got my rebuilder engine, now planning all the ins and outs.


Just wondering - all the bottom end bolts I pull from the motor - will they be good for another 200,000 kms?

Also - what sort of refurb will an average crankshaft need?

[royce]

all the bolts holding bits on, fine
the bolts holding the rods together and main caps on should be ok, can be replaced but not usually done

before you start ripping the engine to bits, go read up on engines and how to do this, some things need to come apart in order, some parts must never be mixed even though they look the same, some parts need to be marked so they go back where they came from

once youve finished reading, read some more! its easy to rebuild and engine but easier to stuff it up

the crank can need a regrind, all the round shiny parts (journals) get ground to a smaller size but back to perfectly round, you then fit thicker bearings to compensate

You might be better stripping all down to the block crank and rods and getting those parts ground bored and honed AND assembled, then you can work on bolting the other stuff back on and not worry about trying to set and measure clearances without the right tools