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propane with dual 4's ???

Discussion in 'The Hokey Ass Message Board' started by rockin rebel, Feb 27, 2011.

  1. any propane specialist here. :confused: I am putting a good 350 chevy, with hardened seats, yes... in a 57 Chev 1 ton truck, for hauling my loaded car trailer with auto or 4 spd, not sure....but I have seen a Model A race with dual 4's on propane....I have a new air gap, dual 4 manifold...........should I, would I.?? thanks guys
  2. Mr_Roboto
    Joined: Jan 4, 2011
    Posts: 24

    from Joliet, IL

    This should work fine with a set of Impcos on it. They are very simple, and usually HP limited. If you're going to run a lower power level you may do two of the 2bbl units with adapters and then use a single vaporizer provided it's adequate for your power levels. If worse comes to worse you could always use a pair of vaporizers as well. The other option is to use twin vaporizers.
  3. newsomtravis
    Joined: Jun 1, 2009
    Posts: 562

    from pville, ca

    well.....depends on you, you have cheap access to propane? takes more propane to make the same power as gas.....hence a large tank for the range and more dollars to fill.....other than that, just have to find a combo that will work like roboto said...not a big wanting duel fuel or dedicaed propane?
  4. thanks .. I do have 3 propane set ups. so lots of parts. also have a big tank or two.

  5. should I use two of everything.???
  6. oops, not dual fuel, we have propane everywhere here and I have heard you don't get as good a mileage with dual..
  7. Check with Franz or Frank (he's on the HAMB- search older propane threads for him) on<cite> this propane forum.
  8. Mr_Roboto
    Joined: Jan 4, 2011
    Posts: 24

    from Joliet, IL

    Something else I will be willing to say is do not be afraid of the some compression with it. It's 104 octane, IMO part of the reason why milage isn't as good with it for a set power level is that most people put them on engines designed to run with gasoline and because of that LPG cripples the real capacity of it.
  9. R Pope
    Joined: Jan 23, 2006
    Posts: 3,309

    R Pope

    A few things about propane I didn't like. Availability, for one. Very few stations sell it, and they aren't easy to find on a trip into new areas. And the tank has to have a current inspection certificate or they won't fill it. The lack of power may not bother you, but I like to keep up with traffic. And if propane is more than about 2/3 the price of gas there's no savings anyway. And if you run right out, there's a towtruck in your future.
    I had several setups, gave them all away and switched back to gasoline. Not worth the hassle.
  10. scottybaccus
    Joined: Mar 13, 2006
    Posts: 4,109


    First, make sure you need two mixers. If you aren't planning to run over 4000-5000 rpm routinely, one is enough.

    If you do plan on twisting the screws, you can use two Impco 425 mixers (470 cfm each) with two Model E or equivalent vaporizors. You will only need one fuel lock-off valve. There is not much concern about over carburerating with these because they are vacuum actuated, so they will only open as much as the engine demands. If you run a 1:1 linkage, you will want a long throttle lever or a progressive lever to manage the off idle ramp up, or use a progressive linkage that only gets on the second mixer at high throttle positions.
    I'm using a matched set of holley base plates from a couple of 600 cfm carbs. They have 1 9/16 bores. I have a neat trick to convert the vacuum secondary linkage to a 1:1 mechanical linkage.

    All the debates about losing power are bunk. Propane produces fewer btus, yes, but you can optimize an engine to exceed pump gas power on propane. IF you could run race fuel all the time, you could make more power on gasoline, but propane can beat 89-94 octane fuel with the right engine combination.

    Ignition timing is important. Propane likes modest curves with minimum initial advance.

    Cam selection is the most important part of getting the bang for the buck. Narrow lobe separation angles make the most of it. I chose a Thumper cam specifically for that reason.
  11. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 8,933


    Plenty of people run propane (LPG) on cars down under. A lot cheaper than gas and a lot more plentiful down here as taxi cabs run this setup for economy given the miles they do annually. Setups are quite tidy nowadays compared to the old fashioned systems form years ago. Some even run dual fuel with gas and propane where sufficient space exists for two (2) tanks. I just put it on my Explorer and can switch from LPG to gas and vice-versa or run on either.
    Last edited: Feb 28, 2011
  12. striper
    Joined: Mar 22, 2005
    Posts: 4,498


  13. chevyfordman
    Joined: Oct 4, 2008
    Posts: 1,074


    I've been running propane on my 71 ford pickup for over 25 years at least, my truck sits a lot anymore so it works better for me than gas though my truck is a dual fuel setup. I have a place where I can fill up my truck, myself, anytime and propane is about $1.29 a gallon. I get less mileage and a little less power, I had the truck set up by a propane place , very expensive system to install so it will take a million miles to break even. Not quite that bad. But I'm happy with the way the truck starts and runs and you must force yourself to change oil as it stays very clean. I've had this truck since Jan of 71 so if I was on gas I probably would have had to rebuild the carb several times.
  14. customcreationsllc
    Joined: Mar 3, 2011
    Posts: 25


    Figure I would just add is a pretty good source of parts and knowledge.

    I've been told propane has about 10% loss if run at gasoline spec engine.
    But since it is like 100-105 octane you can bump up the compression ratio and timing and get your power back.
    And almost impossible to stall unlike gas it is already atomized and you can idle down in the low hundreds.
    And the mileage is about the same for both. And you oil will stay cleaner a lot longer.

    I'm next rig is going to run off propane so I'll let you know how it is in a couple years.
  15. I thought that you could have more initial advance with propane.:confused: What's your idea of minimum?
  16. special-k
    Joined: Mar 24, 2009
    Posts: 45


    I had a daily driver on propane system and never had any big issues. This was a propane only system which would be the only way I'd go. I brought it home one night on a BBQ tank. All you need is a hose adapter.
  17. xr van
    Joined: Apr 28, 2011
    Posts: 17

    xr van

    hey there

    i am currently building a turbo charged propane v8 for a 60s falcon project i am doing. Propane is a fantastic fuel as long as you follow a few simple rules. I am going to refer to propane as gas as that is what we call it here in Australia sorry for the confusion.

    1. use an open plenum manifold. propane or gas is introduced to the motor as a gas so using a single plane manifold or tunnel rams for twin mixers will only be a benefit for two reasons. There is more room for the extra volume (gas and air mix) to exist in the plenumof the intake and the gas in your air mixture will not fall out of suspension and pool in the manifold (unlike gasoline) as it exists as a gas at normal atmospheric temperatures.

    2. Your ignition system needs to be up to scratch. Gas is a fairly hard fuel on you ignition componenets especially on your leads and plugs. In an older vehicle a good electronic ignition setup with good quality leads will be your best friend and prevent intake and manifold backfires. Gas also requires more initial timing than petrol but requires less total timing. For example on a cleveland v8 the perfect timing curves for a car with a relativly standard cam would be 14 degrees intial with about 28-32 degrees total timing all in by about 3000 rpm. So get your dizzy recurved to suit!

    If you need any more info regarding cam choices or how good gas is with forced induction message me and i will be happy to share some info. For a cheap fuel with a higher ron than most premium pump fuels, it has a few bad stigmas attached to it that it does not deserve. It isjust people trying to run it on engines that are designed to run on a completely different fuel. Build a motor for gas and it will run as well and also idle smoother that its gasoline brother..

    cheers dell

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