Building an engine to run on propane.

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  • crow223
    232 I6
    • Aug 15, 2007
    • 110

    Building an engine to run on propane.

    Hi guys,
    I'm just getting started on my chevy 350 propane build.
    Just wanting the benefeit of your experiences running on propane.
    I just have a few questions.
    Do I need to run hardened valve seats?
    What's the ideal compression ratio? I'm leaning towards 11:1.
    What cam specs am I looking for?
    Any other suggestions would be greatly appreciated.
    Thanks,
    Dan
    77 J10 350/700r4/np208, lockrite rear, 3" Rough Country lift,xrc8 winch,33" MTZ's
  • Fiodh. Argus
    350 Buick
    • Jan 01, 2005
    • 1280

    #2
    hello
    I am running propane on my 360 Cherokee and found it to be simple and straightforward, and works excellent.

    For sure, 11:1 would be an excellent compression ratio, the higher the better, as rumor has it propane is 101 octane. That ratio might be high for a small block but I am not sure? I think I am running about 9:1 and it's great. (when the jeep's has not broken something else) with hardened high temp pistons.

    hardened valve seats and valves would be ideal too but people don't always get to do that and it seem to work fine for them anyhow. It will help with the higher temps.

    I am running an Erson cam which is slightly more aggressive than the edelbrock peformer cam, a good mid range sports cam. If you could find a cam for low end torque vs. high end HP that might be more suitable for wheelin' but I have no complaints.

    I can say I like propane very much, it's a lot cleaner.

    D.
    Drew
    77 Cherokee WT

    Comment

    • crow223
      232 I6
      • Aug 15, 2007
      • 110

      #3
      Pardon my ignorance, but where do i get hardened high temp pistons?
      I looked at summit racing's website and don't see any listed as hardened high temp pistons. Thanks.
      77 J10 350/700r4/np208, lockrite rear, 3" Rough Country lift,xrc8 winch,33" MTZ's

      Comment

      • Fiodh. Argus
        350 Buick
        • Jan 01, 2005
        • 1280

        #4
        well, prehaps I'm just blowing smoke out my ears but when I got my motor rebuilt at a local reputable shop, the fellow told me he was putting in high temp pistons but to be honest I never got the exact details. Maybe just high temp not hardened? I was under the impression they were higher compression, high temp, hardened...
        Drew
        77 Cherokee WT

        Comment

        • JERSEY JOE
          304 AMC
          • Jan 15, 2004
          • 1591

          #5
          PISTONS

          Perhaps the dome was coated with a high temp ceramic coating? Company called Swain Technology will coat the domes as well as the skirt with anti friction coating.
          1977 CJ 7 360 T-18 IHC D300 FARM TRUCK NY
          1985 CJ 7 AMC 401, CLARK 285SV 5 SPEED, DANA 60, DANA 44, RUBICON 4.5 LIFT. 37 KRAWLERS
          1987 J-20 401 90% COMPLETED.
          1985 J-20 360 6 inch lift, 37's plow truck
          1986 J-20 360 stock well rusted plow truck
          1970 AMX CURRENT PROJECT

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          • Fiodh. Argus
            350 Buick
            • Jan 01, 2005
            • 1280

            #6
            they insited on putting these pistons in when doing the rebuild - I got a 12K 12 month warranty. I thought that was pretty cool and a bit of a suprise.

            Probably 12 months will have gone by and I will still be trying to get this smogged! almost there, getting there...
            Drew
            77 Cherokee WT

            Comment

            • mattmopar440
              AMC 4 OH! 1
              • May 17, 2007
              • 4092

              #7
              mileage

              i was wonderin about propane 2 what your mileage
              what size tank do you use of tank of LP
              87' Grand Wagoneer
              401/727/229, Currently:RUNNING
              84 J10/20 hybrid 258/727/208 Daily Driver
              80' J10 4BT/AX-15/208
              74' J10 Go Grabber Green Sold
              Originally posted by Heavy_Metal_Thunder_81
              Inferior Chevy

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              • crow223
                232 I6
                • Aug 15, 2007
                • 110

                #8
                And to add to matt's great questions, Where did you get your propane tank from? Do you burn a full tanks worth, or can you only use a certain percentage of the tank before pressure gets too low?
                77 J10 350/700r4/np208, lockrite rear, 3" Rough Country lift,xrc8 winch,33" MTZ's

                Comment

                • Fiodh. Argus
                  350 Buick
                  • Jan 01, 2005
                  • 1280

                  #9
                  I'm not a propane expert but wil share anything i can if it will help. The propane system in my jeep has been easy and great to use but the rest of the jeep has been a real challenge, never seems to stay functional for more than a week or two!! This week it was the ignition and a blocked catalytic...

                  The mileage on my new engine running on propane seems about comparable to gas, slightly less in local driving, about 10 mpg. I think my other gasoline motor wasn't running too great and it also got about 10. I drove the jeep about 50 miles a week ago and it used almost 1/4 tank.

                  I got my tank from ebay but really wanted to buy one from Sleeger's Manufacturing in Ontario, Canada (I should have). They have a perfect model for the back of the Cherokee. A 56 gallon (50"?) tank that just fit in the wheel wells at the rear tailgate. It was about $500 for the tank and then $500 shipping. !!! Instead, I found one in San Jose that was a fair bit cheaper, but now I see it's an older tank and is only 50 gallons and I will probably have to replace it some day soon. But I learned a lot from talking to the guy selling it, so not such a loss.

                  This guy was driving a propane chevy 6 cyl truck that he regularly passed smog with, him having done the conversion himself years before. That day, he told me to use cooler spark plugs, advance the timing 10 degrees over stock, and he insisted, insisted repeatedly, that I should disconnect the vacuum advance so the original 16 degrees advance would not cause it to advance too much. (I did run without vacuum advance for quite some time, and it was fine,ran strong and stout, but will be doing more tests with my new HEI, trying less static advance and keep the vacuum.)

                  Yes, propane tanks have only 60% of the tank usable for driving, because the tanks can only be filled to 80% to allow for heat expansion, and also you can only get good liquid pressure down to about 20%... that means on a 50 gallon tank only 30 gallons is usable... which is decent enough for my range and needs but I also carry a spare 10 gallon forklift tank as a sort of jerry can just in case. (6 gallons usable, about 60 miles)

                  Here's a link to a write up when I was doing the conversion two years ago.



                  hope that's interesting and you have good luck with your conversion. Which carb/mixer are you planning on running?
                  Last edited by Fiodh. Argus; 09-13-2007, 09:52 PM.
                  Drew
                  77 Cherokee WT

                  Comment

                  • hcm
                    232 I6
                    • Dec 20, 2005
                    • 37

                    #10
                    My tanks are from National Energy Equipment and are 33 gallons. At 80% full, i get 150-200 miles. 150 when i drive like i stole it (most of the time), and 200 once this summer with my wife and daughters on board. Funny how a co-pilot and two back seat drivers slows you down. I have run the tanks completely dry twice when finding out where on the guage empty really is. I haven't had a problem with low liquid pressure as my tanks are underneath and gravity pushs the last of the fuel into the line. The engine vaccuum draws the fuel into the mixer on demand so it pretty well sucks my tanks bone dry. Use bronze wall valve guides and Colt Cams has 3 propane grinds for a SBC. These have a little more overlap to cool the exhaust valve and seat and slower closing ramps to let the valve down gently.
                    1980 Cherokee 360/727/208 Propane MSD S-10 Steering Rhino Conversion

                    Comment

                    • Fiodh. Argus
                      350 Buick
                      • Jan 01, 2005
                      • 1280

                      #11
                      cool!
                      Drew
                      77 Cherokee WT

                      Comment

                      • crow223
                        232 I6
                        • Aug 15, 2007
                        • 110

                        #12
                        33gallons X %80 =26.4
                        200 miles/ 26.4=7.57mpg!
                        You dragging an anchor behind you or do you just have a REALLY heavy foot?
                        77 J10 350/700r4/np208, lockrite rear, 3" Rough Country lift,xrc8 winch,33" MTZ's

                        Comment

                        • hcm
                          232 I6
                          • Dec 20, 2005
                          • 37

                          #13
                          You can expect up to 30% less mileage from propane.On another propane vehicle i owned, it went from 20 on gas to 18 on propane. It depends on the application and how you drive it. When i drove this Cherokee home, it was on gas. 3.31 gears and 33 inch tires keep the revs low but i still only got 9-10 on the highway. With 180,000 miles, the rings are shot and oil pressure is a rumour. This motor is tired and i am currently building a new one. Lots of compression, ported heads, big cam,headers and the usual hot rod stuff. Around here, the price of propane is $.62 per litre. Premium is $1.15, so i don't mind the mileage loss. Or i could slow down......
                          1980 Cherokee 360/727/208 Propane MSD S-10 Steering Rhino Conversion

                          Comment

                          • Richomino
                            232 I6
                            • Dec 30, 2005
                            • 132

                            #14
                            Hey Crow!

                            Most all engines that came from the factory with unleaded heads already have hardened valve seats......I've heard you can get 'harder' seats such as stellite, but i run regular 360 heads....

                            11:1 sounds great for propane......

                            I guess you have a HEI, so theres plenty of info on tweaking it...look for more advanced static/ initial timing, and a 'faster' advance curve (Total timing coming in sooner).....also, run no vacuum to the distributor.

                            You shouls also use colder plugs.....
                            Richo
                            80 CJ-7
                            360 on Propane
                            TF-999 / Dana300
                            SOA/SRS
                            36" Iroks
                            FSJ 44/20

                            Comment

                            • danielheren
                              232 I6
                              • Oct 25, 2009
                              • 76

                              #15
                              I run propane in my 74 J20

                              I run my propane tank empty w/o any problems. According to the table below, at 0 deg. F, propane in a tank would have 24psig. The warmer it is, the pressure goes much higher. My truck's 360 runs like it's got a TBI setup. As a matter of fact, it runs better than my wife's G. Waggy which has a Howell TBI/HEI setup. She's jelous.

                              Also: When you are having the tank filled, the "bleeder" valve or "fixed liquid level valve" is opened only to help determine when the tank is 80% full. There is no "air" in a propane tank, but only liquid or vapor propane. Some propane tanks get filled by weight only and not by checking the liquid level valve which spews white liquid propane when filled to 80%. So, they're not actually venting the tank when filling it.

                              Here's a link to the info below http://www.propanecarbs.com/propane.html

                              There is a ton of info on the internet re: propane

                              "Does the amount of Liquid effect the pressure inside a propane storage container?
                              No. And important fact to remember is that since the vapor pressure inside the propane container is governed by ambient temperature outside the container not the amount of liquid inside. A container that is 1/4 full at 80 degrees will contain the same vapor pressure as a container that is 3/4 full at 80 degrees. The vapor pressure is not generated by the amount of liquid in the tank. As long as there is some liquid and not more than 80% liquid inside the container, ambient temperature outside the container will govern the vapor pressure inside the container."

                              Table #1 lists the vapor pressure inside a propane container, at a particular temperature, containing some liquid but not more than 80% total capacity. This allows for a 20% vapor space



                              Table #3 lists the similarities of water and propane

                              Last edited by danielheren; 11-20-2011, 10:07 PM.
                              74' J20

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