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Old 09-13-2007, 05:41 PM
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crow223 crow223 is offline
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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
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Old 09-13-2007, 06:10 PM
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Fiodh. Argus Fiodh. Argus is offline
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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.
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Old 09-13-2007, 06:48 PM
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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.
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Old 09-13-2007, 06:57 PM
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Fiodh. Argus Fiodh. Argus is offline
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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...
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Old 09-13-2007, 07:05 PM
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JERSEY JOE JERSEY JOE is offline
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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.
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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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Old 09-13-2007, 08:12 PM
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Fiodh. Argus Fiodh. Argus is offline
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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...
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  #7  
Old 09-13-2007, 09:25 PM
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mattmopar440 mattmopar440 is offline
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mileage

i was wonderin about propane 2 what your mileage
what size tank do you use of tank of LP
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  #8  
Old 09-13-2007, 09:28 PM
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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?
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Old 09-13-2007, 10:45 PM
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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.

http://www.fiodh.com/cherokee/propane.html

hope that's interesting and you have good luck with your conversion. Which carb/mixer are you planning on running?
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Last edited by Fiodh. Argus : 09-13-2007 at 10:52 PM.
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  #10  
Old 09-13-2007, 11:20 PM
hcm hcm is offline
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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.
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  #11  
Old 09-14-2007, 08:49 AM
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Fiodh. Argus Fiodh. Argus is offline
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cool!
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  #12  
Old 09-14-2007, 04:18 PM
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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?
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Old 09-15-2007, 02:41 PM
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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......
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Old 09-17-2007, 09:47 PM
Richomino Richomino is offline
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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.....
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  #15  
Old 11-20-2011, 10:42 PM
danielheren danielheren is offline
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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

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Last edited by danielheren : 11-20-2011 at 11:07 PM.
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  #16  
Old 11-21-2011, 02:48 AM
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Quote:
Originally Posted by Fiodh. Argus
Here's a link to a write up when I was doing the conversion two years ago.

http://www.fiodh.com/cherokee/propane.html

thats a great write up - maybe you can submit it to the technical library on these boards - as I'm sure 'pane is going to gather further momentum.

me, i run dual fuel - i have an impco 300 mixer sitting on top of the carb & a 60L tank down back where the spare tire used to be. this is a really common set up for SJ wagons in Australia. i run it on petrol one day a week just to keep the gaskets & seals etc in the fuel system supple.

i just had my engine rebuilt & went with an "RV" stage 1 cam, hardened valves & stainless guides specifically for propane although i believe any engine built for unleaded is unlikely to have any severe valve recession problems. but as an extra precaution i'm also about to install a valve saver kit - have a read HERE & HERE. this system apparently keeps the top end lubricated, so i figure its a bit of insurance & extra peace of mind.

i also run an oil specifically blended for propane - again for peace of mind, HERE.

the only issues i encounter is a compromise with the fine tuning as i do run it on both fuels & the engine should be advanced for LPG.

i'll have the LPG system looked at in a few weeks & get her onto a dyno too.

good luck, i'll try to help you out any way i can...
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  #17  
Old 11-21-2011, 01:28 PM
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But thanks for reviving it. You saved me from having to hunt for it. I'm getting ready to convert my '74 J-10 over to LPG
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Hi my name is Keith; I have Obsessive–Jeep Disorder (OJD) : a mental disorder characterized by intrusive thoughts that produce anxiety, by repetitive behaviors (buying parts and more Jeeps) aimed at reducing anxiety, or by combinations of such thoughts & behaviors such as but not limited to working on said Jeeps for extended hours.
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