"LPG only" conversion

Discussion in 'Fuel Economy & Emissions' started by Harry Clamshell, Aug 1, 2008.

  1. Harry Clamshell

    Harry Clamshell Well-Known Member Charter Member

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    I'm now in the middle of the process to convert my 73 Riviera to burn only
    LPG. At this moment it still can use regular gas or LPG with the Impco 300A
    on the Q-jet; but why should I use gasoline (with or without ethanol) at
    over $10 p/gln when LPG cost me only $3.00 gln. (I admit there are no environmental, only economic issues for this change. Still LPG burns a lot cleaner than gasoline)

    Having the 455 use LPG with the 300A decreases power with about 10%, but now converting to Impco 425 (uses only the Q-jet"s throttle plate, so now I can use the original air filter housing) there won"t be any power loss.

    LPG preferably needs cold intake air, so I converted 2 air filter housings
    (the big ones from a 75 Big Buick with the duct going to the front of the car) to one
    with dual snorkel (need to replace the battery a few inches)

    The 455 in the Wagon will get the same next year
     
  2. HandyAndy

    HandyAndy Well-Known Member

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    :confused:
    What about the tank? Custom?
    Does it have to be external?
     
  3. Harry Clamshell

    Harry Clamshell Well-Known Member Charter Member

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    There is an additional tank in the trunk for 27 gallons )which can be filled, due to a safety device, for only 80%. I will upload some photos later.
    In fact I can get rid of the original gastank and add another 20 gallon tank
     
  4. HandyAndy

    HandyAndy Well-Known Member

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    Oh, this car isn't a wagon...:16suspect1:
     
  5. Senri

    Senri Well-Known Member

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    That was exactly my plan aswell. Using only the Throttle plate will certainly increase power and mpg. You can also install the right advance curve for lpg now.
    With you wagon, you could have the advantage of placing a tank at the place of the original. That way, you don't loose space and if your car has that, could keep a functional 3rd seat.
    Keep us posted!
     
  6. Harry Clamshell

    Harry Clamshell Well-Known Member Charter Member

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    the tank issue for the wagon remains, for I will have to use a tire shaped (ring) tank which has a few cons. Still got a few months to come up with a solution: 3rd seat has to stay and no tank visible from the outside of the wagons!!

    This is how the LPG set-up in the 73 Riviera looks now:

    You can clearly see the evaporator (with cooling hoses to/from heater) and the "LPG-arm" with the air filter:
    [​IMG]

    LPG-tank in the trunk:
    [​IMG]

    And for the spare tire (I used the smallest tire to fit a 5x5 7j Buick wheel):
    [​IMG]

    switch on the lower dash: LEDS as fuel gauge for LPG and a switch between LPG or Regular
    [​IMG]
     
  7. Harry Clamshell

    Harry Clamshell Well-Known Member Charter Member

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    BTW: this is the air filter housing I made from 2 others (had to cut one snorkel and welded it upside down). It will provide cooler air than the original air filter (there will be duct added to the front of the car).

    [​IMG]

    The throttle plate from the Qjet and the 425 added:

    [​IMG]
     
  8. Roadking41A

    Roadking41A Well-Known Member

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    Do you have to raise your engine compression?
     
  9. wagonmaster

    wagonmaster Administrator Staff Member Moderator

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    Interesting... I have never seen detailed pictures of a LPG conversion. Can you buy cars that are sold new that use LPG?
     
  10. Senri

    Senri Well-Known Member

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    I don't think I have seen them new from factory (but please correct me when I am wrong), but I have seen them new from the dealer. That is actually a real step forward. On new cars, the system is intergrated with the injection system and before, if you had some trouble, the dealer would point to the LPG converter and vice versa. I have now seen lpg conversion done by the Chrysler dealer for free, when purchasing a new car.
    CNG cars can be bought new from the factory though. I have seen them from Fiat, Volvo, Saab etc. Often called ECO, or Bi-Fuel or so. Great advantage is the intergration of a tank into the car design, so no loss of space.
     
  11. Stormin' Norman

    Stormin' Norman Well-Known Member

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  12. oldcoot

    oldcoot New Member

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    LPG octane rating

    FYI lpg, propane typically, has an octane rating of 110 to 114, so you can run some ungodly high compression ratios. I have seen 12.5 to 1 on several street cars with no problems. With higher cp's and advanced timing you can gain back most of the power lost to the change over. Dual fuel conversions make it tougher to make that power back.
     
  13. Tarjeinorway

    Tarjeinorway Active Member

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    I do a LPG conversation on my 73 Estate Wagon for 5 years ago. I have a lot of photo on a thumbdrive, and will post them later. Someone mean that LPG will destroy heads, but I open the heads just for looking at the valve seat,( after driving 30K ) and they was absolut fine.
    . 2013-12-15_16.22.45.jpg 2013-10-04_19.09.07.jpg imag0379.jpg
     
  14. Silvertwinkiehobo

    Silvertwinkiehobo "Nothing is foolproof as fools are ingenious."

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    The reason why everyone thinks "regular gasoline" cylinder heads don't work with unleaded or LPG is the lead factor, the tetraethyl lead added as an anti-knock compound. The prevailing thinking is that the leftover lead protects the valves from wearing out, which on much older cars from the 1930s to the early 1960s, was a problem. But with newer alloys in the cast iron and the steel in the valves, it's my opinion that unleaded fuel either does not affect them or only affects them so little as to not be noticed. I've never pulled '74 and earlier heads off engines in the last 20 years after running unleaded fuel, to find sunken or burned valves. I've seen sunken and burned valves more on leaner-burning unleaded engines.
     
  15. Harry Clamshell

    Harry Clamshell Well-Known Member Charter Member

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    Do you have a 2 or 3 seater? Specially interested on the whereabouts of the propane tank(s).
     

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