I purchased a propane powered F700 truck chassis off eBAY last year. It used to be a tanker truck for propane but that was removed before I got it.
When driving it down on a Heavy Equipment in transit tag that I had borrowed, the truck ran out of fuel cause of a faulty gauge on the side propane truck which didn't read how LOW it actually was. Finding next to no where to get propane for it, we converted it to gasoline using a new Edlebrock 4-bll from PepBoys, an electric fuel pump wired in and a side mounted metal cylinder shaped gas caddy that held 15 gallons.

Needless to say before my great move to a new location 40 miles away, 2 countys over, I had a rash of vandalism, including my carb being stolen. Not wanting to pay $750 to have it towed, I purchased another identical carb and had it placed on.

It seems like the 750cfm is just too much for this motor and it backfires out of the exhaust under moderate or worse load. Is there a better sized carb for it? Or since it has a rebuilt Jasper unit in it, what do I have to do to make it EFI? I assume the manifold has to be changed out since it has some type of tall pedastool (A high rise?) that all the carbs sat on.

I decoded the VIN and placed it here. I figured somebody in the KNOW would be able to tell me if do to it being a propane powered unit from the start, what would I have to get from a boneyard to make it like it was a normal powered EFI unit from the same line of assembly? Do I have to put some type of emissions like gadgets on it, or are such large trucks exempt for that model year? I assume they have computers as well.

All my large trucks are either OLD (1982) or are Mechanically injected diesels from around the very late 80s to early 90s. This is my first Large Ford, I have GMC 7000s and Kodiak Topkicks for the family contracting business. I have tons of smaller ones like Econolines and a few 83 to 96 era pick up trucks.
<table border="0" cellpadding="6" cellspacing="0" width="480"><tbody><tr><td class="pageTitle">VIN Results</td> <td align="right">
</td> </tr> </tbody></table> <table border="1" bordercolor="#cccccc" cellpadding="0" cellspacing="0"><tbody><tr> <td class="pagehead1"> VIN: 1FDXF7087VVA33241
</td> </tr> <tr><td> <!-- Section for positions 1 thru 3 --> <!-- Section for position 4 --> <!-- Section for positions 5 thru 7 --> <!-- Section for position 8 --> <!-- Section for position 10 --> <!-- Section for position 11 --> <!-- Section for positions 12 thru 17 --> <table id="tablegeneral" border="1" cellpadding="2" cellspacing="0"> <tbody><tr bgcolor="#cccccc"><th colspan="2"> World Manufacturer Identifier - 1st, 2nd, 3rd Positions </th></tr> <tr><td>VIN Code:</td><td>1FD</td></tr> <tr><td>Assembly Country:</td><td>USA </td></tr> <tr><td>Make:</td><td>Ford </td></tr> <tr bgcolor="#cccccc"><th colspan="2"> Restraint System Type (Passenger Cars) or Brake Type and GVWR Class (Trucks and Vans) - 4th Position </th></tr> <tr><td>VIN Code:</td><td>X</td></tr> <tr><td>Brake System:</td><td>AIR </td></tr> <tr><td>GVWR Class:</td><td> Class 7 </td></tr> <tr><td>GVWR Range:</td><td>26,001 - 33,000 Pounds </td></tr> <tr bgcolor="#cccccc"><th colspan="2"> Line,Series Body Type - 5th, 6th, 7th Positions </th></tr> <tr><td>VIN Code:</td><td>F70</td></tr> <tr><td>Vehicle Line:</td><td>F-700 </td></tr> <tr><td>Body Type:</td><td>CONVENTIONAL </td></tr><tr><td>Vehicle Type:</td><td>Truck/SUV </td></tr> <tr bgcolor="#cccccc"><th colspan="2"> Engine Type - 8th Position </th></tr> <tr><td>VIN Code:</td><td>8</td></tr> <tr><td>Engine:</td><td>7 L </td></tr> <tr><td>Cylinders:</td><td>8 </td></tr> <tr><td>Fuel:</td><td>Flexible </td></tr> <tr><td>Horsepower:</td><td>218 HORSEPOWER, 213 - 234 HORSEPOWER </td></tr> <tr bgcolor="#cccccc"><th colspan="2"> Model Year - 10th Position </th></tr> <tr><td>VIN Code:</td><td>V</td></tr> <tr><td>Model Year:</td><td>1997 </td></tr> <tr bgcolor="#cccccc"><th colspan="2"> Assembly Plant - 11th Position </th></tr> <tr><td>VIN Code:</td><td>V</td></tr> <tr><td>Assembly Plant:</td><td>KENTUCKY TRUCK: JEFFERSON COUNTY, KY </td></tr> <tr bgcolor="#cccccc"><th colspan="2"> Production Sequence Number - 12th - 17th </th></tr> <tr><td>VIN Code:</td><td>A33241</td></tr> <tr><td>Prod Sequence Number</td><td>A33241 </td></tr></tbody></table></td></tr></tbody></table>

 

During my escape, I had issues with the new carb ranging from Vapor Lock in the 95 degree weather last Sunday to finding the plugs were fouled. We guessed that the plugs were not switched out when it was propane, so it was behind on mantience. Plus when converted it to gasoline, perhaps a different gap and range were required. I replaced the plugs with new ones of the normal gasoline burning type for a 429 and put a new cap and rotor on as well. The wires didn't seem to be unacceptable really and I was short on time as well as my location was a gas station that the truck stalled out in.

 

On a truck that new.... i have no idea, sorry i cant help more.

 

My thoughts on this would be that this new a truck would be fuel injected-so if your changing to a carb you would also have to change distributors to a duraspark from a carbed unit. My guess is that the computor does'nt have enough feedback to advance the ignition properly.
Have A Good Day----Hotwrench