LPG or Petrol???

[xcsam 10]

G'day members, i've got a whole heap of clevo and XC parts in my garage and I am planning a new engine build. I've got 2x clevo blocks that haven't been bored, 4ma crank, some 302 rods, but may possibly get more appropriate ones if necessary (as well as pistons), open chamber 2v heads, Holley 750 vac carby, Tremec 5 speed box and heaps of other stuff as well. Speaking to you guys and an engine builder, the first thing I have to decide on is what I want to the engine to do for me and then decide on the compression ratio.... I want to be able to start the engine and drive, whether it be cruising around town or interstate. I want my engine to sound 'big' and 'nasty'.

 

Initially I always planned to run my engine on straight petrol, but after driving a friend's GU Patrol on gas, I wondered about building an LPG clevo? I can see the financial benefits of filling tank of LPG at the servo vs petrol, but what about performance mods for LPG. I've read that you can build an engine like this to run on LPG or petrol, but not both because if it's tuned/set-up for one, it's not going to be as good on the other fuel.

 

As for performance, I was hoping for 400hp at the flywheel, but it's not essential to get that figure if I cant. I'm planning to build a cruiser, not a race-car. I know that I can get these figures on petrol, but can i with gas?

 

My budget is as little as possible, but it can be increased if necessary. For example, if I had a budget of $4000 to build my engine over 2 years, and you said that i'm going to need $6000 to build the engine, then it would take me 3 years, not 2 (hypothetically).

 

What are my options for an LPG clevo, or should I just stick to petrol?  

[GspecZL 979]

I have a LPG 351. Runs very nicely and doesn't feel like it has lost a great deal of power. With fuel prices the way they are it makes sense with such a thirsty engine.

 

my 2c

[dizzy616 183]

if i where to run a v8 id probably put it on gas. just a bit more cost efficient and put 2 tanks in it you will get some decent k's

[Thom 6,651]

I'd go fuel as your running a 5 speed, with a small hydraulic roller cam (in the .550"-560" lift range and somewhere around 260-270 degrees duration should sound nastier than it actually is (a comp 270hr springs to mind)), 302 rods and heads, nice and torquey and should be able to see between 11-12 liters per 100ks I driven nicely

[xcsam 10]

I'd go fuel as your running a 5 speed, with a small hydraulic roller cam (in the .550"-560" lift range and somewhere around 260-270 degrees duration should sound nastier than it actually is (a comp 270hr springs to mind)), 302 rods and heads, nice and torquey and should be able to see between 11-12 liters per 100ks I driven nicely

 

So something like this wouldn't work as well on LPG?

[Thom 6,651]

It would work, it just wouldn't make the same amount of power

[bear351c 10,270]

It really is a budget thing. I've run both, but, prefer PULP. Build the engine for the fuel you will run. You have stated that the engines dont run perfectly on dual fuel, which is true. Buy the cam, o/haul the heads, compression ratio etc for LPG, and it will run close to your 400 flywheel ponies. Gas Research Aust (I think?) had good systems for straight gas, but there are a couple of ways to go.

 

Had my XB ute 351 on gas for 2 years, running twin converters, and 100 litre tank. Regraphed dizzy and had a heap of fun.............

 

There used to be a gang in Adelaide (Competition Automotive, if I remember right) ran an XA ute, bright orange paint and a 460 on LPG at the drags.

Sounded friggin awesome !!!!

[Thom 6,651]

Lpg will work for what you want, but performance lpg setups are a funny thing and can end up chewing most of your engine budget, rather than spending the coin on the engine itself

[Trev Vaa 1,185]

its so easy to get 400hp out of a clevo now its not funny. and you will get bored of it.

i suggest you set your goals a little higher and spend a bit more. this clearly isnt going to be daily driven if you are expecting to spend the next 3 years saving for the motor.... if it is, i would go with gas, if its not id go with petrol, you wont spend enough on fuel to make the conversion worth while, if you buy all the LPG parts new it could easily set you back over 2500$ plus tuning and signing off on the installation.

[revhead 1,392]

im going to run straight lpg on my 351 xe just so over the bullshit price of petrol,

[xcsam 10]

What sort of price difference in the initial costs of building the engine would I see with petrol vs LPG? Obviously building a dedicated LPG clevo would be significantly more expensive?

[Thom 6,651]

Not really (other than the lpg setup itself) basically you build it the same as fuel but different cam selection and higher comp

[PRO250 1,506]

 i looked at it last year on the ute as its a bit on the heavy side to run but i dont drive it anymore that and its engines out for upgrades so im not going to do it and if the use is limmited i would not do it as it would not pay for itself for some time 

clevos and LPG is not a new thing fast and LPG on a clevo not a lot of people do, it but thats not saying it cant be done but if its not worth the cost of the conversion it may not be worth doing  

[xeeclipse 37]

I'd go fuel as your running a 5 speed, with a small hydraulic roller cam (in the .550"-560" lift range and somewhere around 260-270 degrees duration should sound nastier than it actually is (a comp 270hr springs to mind)), 302 rods and heads, nice and torquey and should be able to see between 11-12 liters per 100ks I driven nicely

 

11-12 litres....can we please get off the weed people!

[gerg 10,871]

If building for LPG, I'd go with 4V heads. LPG needs more breathing ability than petrol to make the same power. Velocity through the Venturi and thus fuel atomisation is not an issue with LPG, so bigger is always better. Use an open plenum single plane intake, with twin mixers if possible. Closed-chamber heads and 11:1 comp, 302 rods with 4ma crank. STD volume oil pump.

 

I have little info on what cam to use but I'd say you could go fairly lumpy and the gas will tame it somewhat. Something like a comp 270h, 280h or equivalent will be fine.

[Thom 6,651]

If building for LPG, I'd go with 4V heads. LPG needs more breathing ability than petrol to make the same power. Velocity through the Venturi and thus fuel atomisation is not an issue with LPG, so bigger is always better. Use an open plenum single plane intake, with twin mixers if possible. Closed-chamber heads and 11:1 comp, 302 rods with 4ma crank. STD volume oil pump.

 

I have little info on what cam to use but I'd say you could go fairly lumpy and the gas will tame it somewhat. Something like a comp 270h, 280h or equivalent will be fine.

I'd agree except for the 4v part, they really are too big even for a 351 on straight gas, it would be real doughey and flat down low but up in the rpm it would sing, the killer setup would be 4v's with tounges though, keep the airspeed up to remove those exhaust gasses (they also fix the problems with the short turn radius in the exhaust port)

[Trev Vaa 1,185]

for the money better off spending the money on AFD 2vs.... they'll only cost $2-300 more by the time the 4vs are finished and they will make way more power.

[Stevemack 122]

I've just removed all my LPG stuff from my clevelend, it was running GAs Research throttle body and B2 mixer, it was so reliable, i converted it back when LPG was 11c per litre. It was great fun, but it used to get 5ks per litre of LPG and that was tuned.  In my opinion stay with fuel, LPG will serve no other purpose than to make you a bit different than the rest, but economy for your wallet you won't get.   Gas research stuff aint cheap either, but it's the best LPG stuff around imo.  I'll sell you my stuff if you still want to go that way though.