Outer Limits 4x4 Board

I have an old Jeep with a 360 V8 in it (sorry, flame away.....)
I've rebuilt the top end, new mild cam, head work, performer and 470cfm truck avenger. And new HEI dizzy, leads, plugs etc

i also got a gas set up off another rig, and put this on so i can actually get some decent range in the bush out of it running dual fuel.

Seems though the thing isnt running right on gas. Its an Impco CM425M-2 mixer. WIth the gas hat on, it struggles to build revs down low, wont start on gas when warm, and runs way rich. Seems to clear up OK mid revs (ie 3000) and goes ok from there. But down low, its like its strangled.

Take the gas hat off, stick an air cleaner on it and it runs fine on petrol (maybe a tad rich, minor jetting to be done). Actually, it hauls.....

i think this mixer works on vaccum? to open the diaphram so it will run on petrol?

It has a 'balance' adjuster on one side? What does this do?
Idle adjustment on the other side, fair enough. There's also a 1/2 in spring loaded bolt, is that some sort of adjustment?

Do i need a bigger mixer? Is the 425 part referring to cfm?
Or is it another issue, ie the diaphram damaged/not opening?

The cam is quite mild with minimal overlap which i understand gas doesnt like. From my knowledge gas likes high lift/short duration minimal overlap.

Any thoughts/knowledge appreciated. I'm reasonably handy mechanically, but not with gas mixers. Cheers.

post up some pics of your set up if possible.
to me it almost sounds like its running on petrol and gas. but im sure that isnt the case.

I should clarify- it runs like crap on petrol (as well as gas) with the gas hat/mixer set up on it- but much better on petrol with the gas hat removed and just an air cleaner on the carb. Thats why it makes me think the diaphram is stuffed or the mixer too small.

Will post pics next day or so.

Here's pics of the gas mixer and top hat...

do u have the timing set for gas when u run it

Where in Melbourne are you? I don't know a lot about gas but i used to take my dual fuel mitsubishi pajero to Vito at AVS Auto in Hoppers Crossing.

He is excellent with all things LPG, conversions, break downs etc. He fixed an ongoing problem i had with mine that another so called LPG 'expert' thought he had fixed.

Give him a ring, his number is 0418 553 453.

GUtripper wrote:I have an old Jeep with a 360 V8 in it (sorry, flame away.....)
I've rebuilt the top end, new mild cam, head work, performer and 470cfm truck avenger. And new HEI dizzy, leads, plugs etc

i also got a gas set up off another rig, and put this on so i can actually get some decent range in the bush out of it running dual fuel.

Seems though the thing isnt running right on gas. Its an Impco CM425M-2 mixer. WIth the gas hat on, it struggles to build revs down low, wont start on gas when warm, and runs way rich. Seems to clear up OK mid revs (ie 3000) and goes ok from there. But down low, its like its strangled.

Take the gas hat off, stick an air cleaner on it and it runs fine on petrol (maybe a tad rich, minor jetting to be done). Actually, it hauls.....

i think this mixer works on vaccum? to open the diaphram so it will run on petrol?

It has a 'balance' adjuster on one side? What does this do?
Idle adjustment on the other side, fair enough. There's also a 1/2 in spring loaded bolt, is that some sort of adjustment?

Do i need a bigger mixer? Is the 425 part referring to cfm?
Or is it another issue, ie the diaphram damaged/not opening?

The cam is quite mild with minimal overlap which i understand gas doesnt like. From my knowledge gas likes high lift/short duration minimal overlap.

Any thoughts/knowledge appreciated. I'm reasonably handy mechanically, but not with gas mixers. Cheers.

hey mate i was running a 425 on my straight gas turbo, so it will be big enuff for the small 8 i say small cos they will run perfect on strokers 2

the bal port is so you can attach a refrence line (balance line) between the mixer and converter (try doing this it might lean out your idle)

ok few things to check here, does the mixer whistle? a properly tuned 425 should whistle at idle (best way to know if its set properly)

the big screw is your power valve, little one is idle mix

also your converter might have a rich spring setting, which is bogging you down low, look for a blue or silver spring, if its gold then ditch it hope that helps

oh and if you need more info www.performancelpg.com has a bit on it, or just post and ill try help ya

OK, thanks Cooki Monsta, will give me something to check over weekend.

hi man,

360 is a NICE engine

that carb to 425 adapter you have KILLS the flow to teh top of your carby. It screws it up bad. get rid of it!!

i doubt you have hood clearance problems so get a adapter that does not kink down like teh one you have.

the carby you have is WAY too small for the 360. it will give you alot of torque down low but will not flow enough for a 360 in general.
you need to adjust the " power" nut/screw to get the gasflow right to suit the airflow going into your engine, it may clear up the hesitation down low, but i would fix the adapter first.

not starting on gas is probably the idle mixture, BUT because of the way the 425 is setup you may need a purge of gas to start it.
Try this as a workaround===>, before you turn on the ignition to start it, push the gas pedal to the floor and turn the ignition on to reds, this will flick on the gas and then the safety will gut the gas. Once the gas is cut, take your foot off the throttle and then start it. this sill give the engine a gutful, and start it.

JEs

Thanks JEs,
i was aiming for 250-270hp, and thats about what i got..... i didnt want a 670 cfm or 770 truck avenger, as i aren't chasing big hp.

Compared to the std 2 bbl 190cfm Motorcraft, the 470 is the guts. Combined with cam and intake/zorst, its a nice combo. And makes good grunt right off the bottom through midrange which is where i want it.
Besides, i also want SOME level of fuel economy in the bush when i'm running on petrol and LPG isnt available.

Will talk to a local gas shop about the intake/gas hat, was wondering about that. And thanks for the info re the idle setting and starting. Will give that a go over the weekend.

hmm another thought, altho that hat should flow fine into the carby, but thats just my 2c, go to a 300A mixer and hat, they have a wider intake and flow is almost as good as a 425.

how ever your idle sounds rich, also make sure that hat isnt clogged with crap, and that diaphram moves freely my old one was sticky and it used to jam causing starting issues

OK, just an update..........

Got it running OK, the idle was set way too low, and have screwed the power adjustment up a bit which also helps. Seems it was running way too lean once it had the new cam etc.

re the gas hat, I've had a couple of prices of UP TO $500 (WTF!!!!!) just for the gas hat. They're dreamin....

Can anyone in SE burbs (say Mt Waverley to carrum) recommend a GOOD reasonable gas conversion place? It has gas that was installed in April last year, but I also have a 2nd tank to be installed that needs recertification and hydrostatic valve, dual filler line etc. I have about 3 m of line, lots of fittings, brackets and tank already.....I was quoted $600 plus extra parts required plus certification cost ($200... ???) at one place. I cant believe the $$ these guys are asking for a relatively simple job- check tank, install valve and hook up lines.

Or do all gas installers have their heads firmly up their own asses? (sorry-- the ones i've spoken to so far anyway.....)

GUtripper wrote:OK, just an update..........

Got it running OK, the idle was set way too low, and have screwed the power adjustment up a bit which also helps. Seems it was running way too lean once it had the new cam etc.

re the gas hat, I've had a couple of prices of UP TO $500 (WTF!!!!!) just for the gas hat. They're dreamin....

Can anyone in SE burbs (say Mt Waverley to carrum) recommend a GOOD reasonable gas conversion place? It has gas that was installed in April last year, but I also have a 2nd tank to be installed that needs recertification and hydrostatic valve, dual filler line etc. I have about 3 m of line, lots of fittings, brackets and tank already.....I was quoted $600 plus extra parts required plus certification cost ($200... ???) at one place. I cant believe the $$ these guys are asking for a relatively simple job- check tank, install valve and hook up lines.

Or do all gas installers have their heads firmly up their own asses? (sorry-- the ones i've spoken to so far anyway.....)

Give Mike a call at Auto Gas Connections
Right next to Awill4x4 work.. Andrew swears by their work.