sorry if i'm posting something that someone has already posted but i did spend a fair amount of time trying to search for a thread like this. so i have two main question.

1) if i'm going to do all the usual mods like cam, headers, exhaust ect is a duel fuel car going to perform as well and one that's never touched lpg in its life? (will the car run as good as a straight petrol on when it is in petrol, how will the mods affect it when running on gas and does lpg destroy your engine).

2) Can a car specifically tuned for lpg so much that it wont run one petrol so much that it will start to stall?
(I went to look at an el the other day and the sell was telling me that it was tuned for lpg and he was getting 600k's to a 60l tank of lpg and when i tried switching it over to petrol the thing would cut out so i didn't buy the car thinking that there is no such thing a lpg specific tuning and assuming that the petrol injectors were blocked was i right?)

Thanks guys its much appreciated

depends on the LPG setup as to how much power you will get on LPG or Petrol
Some are better than others - from worse to best IMO

Mixer ring
GRA setup
Vapour LPG injection
Liquid LPG Injection

The mixer ring setup will limit you petrol power as the mixer itself will restrict air flow into engine
GRA T/B are a bit better and have less of an impact

Both the LPG Injected Setups don't interrupt or restrict the Petrol side of the engine, and they are a more efficient setup. so you will make more power on both petrol and lpg with one of these generally

And the car can be tuned to run on LPG better by adjusting the spark map, If it did not run on petrol at all something was wrong
Injectors/Fuel Pump etc

Hi.

The main issue with the typical LPG install is that the LPG mixer is installed somewhere in the intake, and due to the design to allow LPG to work, creates a large restriction which when on petrol does impact on performance at engine speeds above 3000rpm etc.

I ran my wagon with an IMPCO 225 mixer, a Wade 1673 cam, extractors, 2.5" exhaust, and intake mods for close on 2 years. What the engine mods did is provide pretty much std performance while on LPG, with a small increase while on petrol, compared to the same engine without the mixer in place.

Then last year, I installed an LPG Vapour Injection kit that allowed the use of a standard/modified intake allowing the full potential of the engine to be used while on petrol, and provided performance benefits on LPG and an increase in economy on LPG as well.

There are details in my build thread.

Cheers
BenJ

O.k., let me say this: one can either have an LPG tune or a petrol tune. They are different. because:

1) lpg is a higher octane rating than (the current) petrol. BUT, it is a slower burning fuel. Thus, the ignition timing needs to be different to take full advantage of the fuel. Generally, there is a 10 to 15% loss of power with lpg, however, that can be made up with various mods. Mods need to be SPECIFIC for lpg.

You cannot have both. Choose one.

LPG does not destroy your engine, if you have taken the right precautions,

Example #1: my trouble and strife wanted to run her Toyota Camry on lpg. I said the valves will burn out within 100k. Sure enuf, they did. But we have paid the price and had the head modified to suit since.

Example #2: My EL I6 has done 300k on lpg with modified head (3 angle valves, bronze guides etc) and is still running strong. With the mods I have done, it has put out 130+ RWK. LPG is a dry fuel, so you need to take the appropriate precautions

In other words, I modified/built the engine for LPG.



No, but it may run a bit crappy.

E.g.: My EL I6 is tuned as much as possible using the standard ECU for lpg. It pings on a hot day on petrol. But I only use petrol in a REAL emergency.

BTW, I have a Gasresearch system, JMM headers and zorst, and JMM head

Cheers

I've got an impco 300 on a 351 clevo - its duel fuel but haven't bothered with petrol in ages (I know, I should..) - its the setup that has about a foot long aluminium passage hanging off the side of the carby and puts the mixer over one rocker cover - real common old school V8 setup - it goes well but above about 3500 rpm it starts to feel a little strangled...I recently saw that there is another Impco 300 setup that sits entirely above the carby although it sits a little higher and may need a scoop to cover it...(but thats cool...)

Can you LPG guru's comment at all on whether such a setup is better performance wise than what I currently have or am I wasting my time? I was considering a GRA type setup but would I need two of their mixer/carby thingo's for a 351?

I had a Sprintgas setup that sat on the Carter Thermoquad on a 351C, and never had any problems. I never used petrol, and replaced the fuel pump in the engine with an electric pump. I just blanked off the spot where the pump fitted.

However, the engine was bult for gas. As I said b4, tri angle valves, hardened seats, bronze guides etc. The engine did over 300k kms w/out any fuss.



Yes

Thanks mate!

From what I can gather is the OP has a duel fuel car and wants it to go faster.

My opinion is, It's a waste of money to fit an exhaust, cam ect. just to bring the peak power back up to stock yet ruin the economy and drive ability of the car.

The money is better spent upgrading the LPG system to Vapour injection. You'll end up with stock power again, but the up side is perfect drive ability, better economy then the old unmodified LPG set up made AND with room to improve futher.

Quite a few years back I bought a 79 F100 which had a stock 302c running on petrol/lpg (unsure on system) using a Holley 350 with some sort of enclosed air filter hood. It ran OK on both but after my previous 78 F100 which had a 351c I was a bit disappointed with the performance
Anyhow after a year and a half I spun a bearing on the 302c and as I had an old 351c sitting around I decided to upgrade
I did quite a bit of reading and net surfing and ended up using the 30 thou over 351c block with a freshen up (hone, new rings, bearings etc). I decided to use the 302c heads but got them reconditioned with new guides etc and machined to drop the comp ratio down to ~11-1 (unmachined would have been ~13-1, too high). I ran a special mild cam grind recommended by a guy in Adelaide from Crane Cams that was running a Fairlane 351c on straight gas, I replaced the dizzy with a Scorcher dizzy recurved and modded for gas and a higher output ignition

The outcome was like chalk and cheese, massive amounts of power and torque increase which felt even better than the old F100 I had and without any noticeable decrease in economy

The only drawback was that it would ping even on PULP and lacked power above ~3000 rpm Never tried 98 as I generally only used petrol to start and warm up or if the 200L tank ran out (rarely)

I was pleased and amazed how great she ran on LPG with the higher comp, cam, ignition etc
I did always wonder how it would have gone by running a bigger carb as I'd always toyed with the idea of using an old 750 vac sec I had (obviously disconnecting the secondaries 1st) to give a greater airflow Just curious, would that have worked to give more power etc on petrol and gas?

I beg to differ on the whole tune for one - forget the other.

My setup has allowed me to have the best of both worlds and as long as it is tuned appropriately, you also can have the best of both worlds.

Currently I am getting 450km per tank of LPG and 650km on the ULP. This wasn't rocket science and a good LPG tuner will get it spot on for your needs. I use a King injected LPG system and has never let me down but did have some issues with the car recently. As it turned out, a $5 EGR gasket nearly destroyed my engine and now runs a helluva lot better since replacing it(water was leaking into the inlet airflow and in turn to the engine).

Mods stand now with a crane cam(very mild street), Hi-tec headers into standard Cats and 3 inch mandrel bend after the cats, 22lb injectors and a re-tune. I now have 152 RWKW on gas and 151 RWKW on PULP(V-Power)which is nothing to sneeze at. I also plumbed a Flashlube dripper kit into the system when I had the LPG installed - it is a must to use a cylinder lube or you will destroy the valves(unless you harden the seats of course...). I have no room in the engine bay for it so it went under the front drivers side fender behind the bumper( a PITA to refill when you have to!!)

Don';t settle for second best - get it done properly and you will not regret it. That said, don't s**t the installer about the apparent/upcoming mods as they will tune appropriately. If you inytend towing a sherman tank, the tuner will have to know this to set it up appropriately...

Hooroo