LP converted 440 vacuum reading?

[Dunnohow2]

Greetings all,
Does anyone know what the vacuum readings should be for a 440-3 converted to LPG with an IMPCO vaporizer and mixer.
Using the manifold outlet to the power booster was around 14 "Hg.
Thanks,
jenni.

[Dunnohow2]

OK boys and girls, I need answers! Please please a thousand times please.

As some might have read, I'm fitting a new booster and brake m/c.  Booster tests not good. Checked vacuum = 14" Hg at idle. So I checked the forums for optimal readings at various rev ranges, idle and decelerating etc.,and guess what I found...

My unanswered question of 21 Oct 2009!

So, assuming nobody knows the answer or nobody likes me, does anyone have a plan of which vacuum ports connect to which dohickeys.  I couldn't find info in the Dodge RM300 440-3 Workshop manual and parts manual.

Can anyone recommend an IMPCO expert or explain how to correct vacuum levals.  There seem to be pipes which loop from one port to one alongside it.  Is this "normal"?

Is 14" Hg enough for the booster to function?

As before, ALL help will be muchly appreciated.

[DaveVA78Chieftain]

Jenni,
Engine vacuum would be basically the same if you are running on gasoline or propane.  14Hg is normal for an engine at idle which means it is satisfactory for the brake booster.   Typically vacuum only gets higher than that when decelerating.  When cruising vacuum is around 6-8Hg.
Here is a good tutorial about engine vacuum and the vacuum gauge.
http://www.secondchancegarage.com/public/186.cfm

The manual says the RM300 chassis uses a single Master Vac booster (Page 5-49).  Does that match what you have?  Or, do you have 2 vacuum boosters mounted to the frame rail halfway back?  If 2 boosters, then you have a hydrovac system (page 5-51).  We have to know what you have before anyone can assist you.  The single booster Master Vac is much simpler than the 2 booster hydrovac.  Myself I have a hydroboost system that doesn't even have a vacuum booster. 

The IMPCO system was not installed on many rigs so few people here know much about them.  Part of one was on my rig but I never tried to find the remaining parts and try to use it.  IMPCO is still in business so your going to have to google them.
My first impression (from google) is IMPCO wants you to use their dealers.  You sort of get to be the one to learn using propane on a 440-3.

Dave