propane on a 454 with a 6/71 some questions

Propane, Butane, LPG, GPL, C3H8, C4H10
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remco
Posts: 4
Joined: Sat Sep 12, 2020 6:35 am

propane on a 454 with a 6/71 some questions

Post by remco »

Hello,
I have a C 30 dually truck ( a 6000 pound car)
It has a 454 in it and I,m running it now with 1 OHG 450X and a 300 evaporator.
Am going with a 6/71 on the engine. compresion ratio is 8-1 aiming for a modest 10 PSi boost .
Am thinking about this cam from edelbrock 240/246 duration....560/573 lift at valve......112 LSA degree at 110. oparating range 1500-6500
Have a MSD 6A ignition setup .
When I use this formula Replace the 14.7 with 15.6 for propane Than It tels me that I need about 1400CFM of flow
[(DxR)/3456] x [(B/14.7)+1]=C
D = Cubic inch displacement of the motor
R = Maximum engine RPM
B = Maximum blower boost
C = Maximum CFM required
I ques that a 450x mixer flows 450CFM ??? is that correct?
In that case I will need 3 of them,
And 2 650 carbs would be a bit tight, But I do not want to use carbs , I,m looking at Throttle body,s, And here I have a problem, When I look at some charts it say,s that 3 x 60 mm wil flow all that I need, And that seems wrong to me , The carb that is now on the 454 has 4 41 mm valves.
About fuel flow, I can drill and tap the tanks for a extra outlet that is not the problem, Will 2 x 8 mm fuel lines do? that is a 6 mm internal diameter. Have 2 tanks 180 and 230 liters . ( 110 gallon) hope that it will bring me 500 miles

storm
Posts: 706
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: propane on a 454 with a 6/71 some questions

Post by storm »

remco wrote:
Sun Sep 13, 2020 4:02 pm
When I use this formula Replace the 14.7 with 15.6 for propane Than It tels me that I need about 1400CFM of flow
[(DxR)/3456] x [(B/14.7)+1]=C
You are using this formula incorrectly.
Leave it alone as it is [(DxR)/3456] x [(B/14.7)+1]=C
The 14.7 represents the weight of air not air fuel ratio. At sea level air weighs 14.7 pounds per square inch. By my "rough" calculations you will need 1438 cfm.
remco wrote:
Sun Sep 13, 2020 4:02 pm
I ques that a 450x mixer flows 450CFM ??? is that correct?
Approximately.
remco wrote:
Sun Sep 13, 2020 4:02 pm
I,m looking at Throttle body,s, And here I have a problem, When I look at some charts it say,s that 3 x 60 mm wil flow all that I need, And that seems wrong to me , The carb that is now on the 454 has 4 41 mm valves.
What charts are you talking about? Also do you actually mean valves or are you talking about throttle blades?
remco wrote:
Sun Sep 13, 2020 4:02 pm
About fuel flow, I can drill and tap the tanks for a extra outlet that is not the problem, Will 2 x 8 mm fuel lines do? that is a 6 mm internal diameter. Have 2 tanks 180 and 230 liters . ( 110 gallon) hope that it will bring me 500 miles
Don't scrimp on fuel lines, use 10mm internal diameter and be done with it.
Unless you are an authorised LPG technician that is also authorised to "modify" LPG tanks leave the tanks alone.
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456

remco
Posts: 4
Joined: Sat Sep 12, 2020 6:35 am

Re: propane on a 454 with a 6/71 some questions

Post by remco »

Thank youfor the reply.
I took the flow from this website https://accufabracing.com/cfm-air-flow
If I look at this chart I see that the stoch 5L mustang flows 495 I think that that is a 60 mm Trottle body than , but is seems a bit strange and realy small to me .
I do not want to spend a lot of € € € on them, hope I can find what I need at a salvage yard

For fuel lines we do not haven the 10 ID and valves for that overhere ( Netherlands) Max is 8 mm OD
I am not a authorised LPG technician, but have a small machine shop. Drilling and tapping for a extra take of valve is simple .

storm
Posts: 706
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: propane on a 454 with a 6/71 some questions

Post by storm »

remco wrote:
Mon Sep 14, 2020 3:50 pm
I took the flow from this website https://accufabracing.com/cfm-air-flow
If I look at this chart I see that the stoch 5L mustang flows 495 I think that that is a 60 mm Trottle body than , but is seems a bit strange and realy small to me .
You should have noticed that one manufacturers TB may not flow the same as anothers of equal dimension.
Just be aware that carbs and TBs are very different beasts. Comparing the cfm a throttle blade on a carb to the cfm of a TB is a rookie error. Carbs have venturis to help draw fuel through, TBs (usually) don't. Venturis restrict flow but create high vacuum.
remco wrote:
Mon Sep 14, 2020 3:50 pm
For fuel lines we do not haven the 10 ID and valves for that overhere ( Netherlands) Max is 8 mm OD
you might want to have a chat with kikigeek who is also from the Netherlands. He has a Suburban with a 454 and is going through the fuel line thing as well.
remco wrote:
Mon Sep 14, 2020 3:50 pm
I am not a authorised LPG technician, but have a small machine shop. Drilling and tapping for a extra take of valve is simple .
It may be simple but I doubt it is legal even with your small machine shop. There is more to a fuel system than a take off line.
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456

remco
Posts: 4
Joined: Sat Sep 12, 2020 6:35 am

Re: propane on a 454 with a 6/71 some questions

Post by remco »

Thanks ,
I just bought two more OHG 450x mixers . Had a bit of luck they are a bit rare overhere.
So I have 3 now , Hope that Feeding them with 2 evaporaters will do.
I think that engine will not be at WOT long, It,s in a dually truck, Not a race or track car .
The one I had was on a 750 carb , so carb was a lot bigger that what the 450 could flow.
That gives me the question , dous it hurt a lot if I would take the trottle body,s a bit larger that wat is the minimum.
So 65 mm.

storm
Posts: 706
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: propane on a 454 with a 6/71 some questions

Post by storm »

remco wrote:
Thu Sep 17, 2020 7:06 pm
That gives me the question , dous it hurt a lot if I would take the trottle body,s a bit larger that wat is the minimum.
So 65 mm.
Sorry I don't understand what you are asking.
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456

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