Effects of high altitude on LP gas converted engines?

[The_Handier_Man1]

From: Graham  (Original Message)
Sent: 5/1/2004 12:31 AM

Hi again...

I've just been advised that a 1973 Winnebago Brave with a Dodge 440-3 motor running on LP gas is unable to cross the Rockies in Canada because of the effects that high altitudes have on the gas???

Please tell me this isn't true or if it is - gulp - what is my best solution to the problem.  Just spent a king's ransom to have the system re-certified and overhauled!!!

Feeling glum, Graham



From: denison
Sent: 5/1/2004 8:06 AM

Graham: I have no expertise here: But, in all the years of reading articles on the advantages of lpg powered vehicles I have never heard of any issue with high altitudes. My quick internet search didn't turn up a word about it either. With gasoline powered vehicles having carburetors, the high altitude problem has always been of running too rich; but they still ran okay.
I found a link on the internet you might like to read, www.wps.com/LPG/lpg-how-to-book.html, from someone who did his own conversion, to a 1963 car with a 190 engine. Do a "search" for the word -altitude-. He says his ran fine at 9900 feet.
The article makes me want to scrounge an lpg system from a junkyard and try it out in one of my vehicles. 



From: denison
Sent: 5/1/2004 8:09 AM

I meant to type -a 1970 engine-.

At high altitudes you loose a few percent of horsepower for each 1000ft above sea level, and thats true for all vehicles - cause the air is thinner. 



From: DaveVa78Chieftain
Sent: 5/1/2004 8:53 AM

  The only thing I can relate is that the discussions around using catalytic space heaters always bring up an issue about not being able to work at high altitude.  Has to do with lower oxygen level.
  If you get a chance, I sure would be interested in seeing some pictures of your setup.  Especially around the carburator area.  My 78 originally came with LPG however, a previous owner had removed all the components in the carb area.  I still have all the piece parts I removed, but have no idea what else was needed to make the system work on a 440 with a Thermoquad.

Dave



From: zInGiErKiLgOtYaRneR1
Sent: 5/1/2004 6:57 PM

Graham I have the propane set up in a '76 Brave 440 and have not been through the mountains but the previous owner claimed to . Where did you get recertified and how much is a kings ransom? I am in Alberta and need to recertify. If anyone is interested I could post a picure of my carb set up as I'm working on the valve covers.
Hugh



From: denison
Sent: 5/6/2004 11:29 AM

This posting is from Graham in Edmonton, who asked me to forward it.

Hi Dave,
I sent message to the list but it got lost??
4 questions.
1 Dodge MH Manual 11-6 talks about conical washers for exhaust manifold. Mine are flat. Which type should I get?
2 Do the conical ones centre the manifold or something?
3 If I use stainless steel nuts, should I use stainless washers too or reuse old ones?
4 Having difficulty finding a metal flange gasket - needed due to propane heat. Do you have a manufacturer, part# and source to try?
Can you forward to the list and thank the other Dave for the Mr. Gasket #. Managed to get that locally.
Ho hum, many thanks and God bless, Graham

Guesses by denison:
I only recall the washers being very slightly conical, but I didn't keep them.
I dont know if the conical washers have any centering effect - I wouldnt think exact centering of the exhaust manifold is vital. I can only assume the conical nuts help to keep the manifold snug after the stud stretches slightly, but still allow it to move slightly as a result of expansion and contraction. I dont have them on my manifolds now, and everything has been fine for over 10 years. I also make it point not to over-torque my manifolds fasteners.
If you use non-stainless steel studs you can use stainless nuts. It wont matter if the washers are stainless. I would reuse the old ones if they arent too rusted. If you use stainless steel studs, you should NOT use stainless steel nuts, to avoid the nut siezing onto the stud eventually.
I dont know where to find a metal flange gasket. The original mopar # is 1924887 for the two gaskets on the 413 exhaust pipe to manifold joint. The exhaust pipes should project up into the manifold slightly, and hopefully this would protect the gasket from some of the heat. When I put my exhaust pipes back onto the manifold flange, I used antisieze compound of course, then added extra nuts on the stud, just to keep the threads from sticking out where they would get so rusty.



From: Graham
Sent: 5/7/2004 10:39 PM

Well at least I tried!

I spent the day cleaning all the parts, removing old gasket material and cleaning the head faces, chasing all nuts and bolts, gooping nickel paste on anything that moves and put everything back where it had come from.  Refilled the coolant, fired up the motor which started first time and the manifold is STILL LEAKING!

I used the Mr. Gasket which didn't seem too good a fit as far as the embossed bits lining up with the ports are concerned, but it looked OK.  Fitted all the bolts and nuts and washers including spring washers which came with the gasket set, tightened them bit by bit in a circular direction from the centre out and torqued everything up to 20 ft lb.  Fitted the flange and gasket, then the exhaust clamp.  All a la manual.

So PLEEASE help me - what have I done wrong?  The LPG conversion guy I went to, told me he doesn't use a gasket when the manifold has been milled, just uses the nickel paste.  Has anyone tried this?

At least I now know how to dismantle and reassemble the manifold.

Feeling a bit down but not yet defeated.

Hope this meassage gets posted this time.

Many thanks for all the ideas, especially the tap and die thread chasing,

God bless, Graham
Any ideas - use no gasket, two gaskets, regular gasket?