Hey All,
Just finished up my LPG conversion on my '78 FJ40. I am sure some of you have seen some threads I have posted for help, but I thought I'd start my writeup. I still have some tuning to do since I am getting horrible mileage - I think I really need to get my dizzy recurved and I have to get an AFR setup to find out where I am on mixture. I'll add that to this writeup as I get that done.
My main concern was that I was getting some carb stumble out of my 38/38 Weber, which had previously served me really well. I never could seem to get the mixture right and since my Cruiser "Dozer", is mostly a trailer queen, I decided an LPG conversion was a good option. I looked at doing the 2FE, but have domed pistons so I scrapped that idea.
I started off by buying a "kit" from a fellow Mud member. It included an Impco 425 mixer, Model E evaporator, vacuum lockoff, fuel pump blockoff plate, heater hose taps, vapor hose, and a Offenhauser dual-plane intake, as well as a Holley (650?) vacuum secondary throttle plate. I picked this up for $400 and added the high pressure hose for $68 from Nash Lift Truck Supply Co. - Clark Forklift Parts, Caterpillar Forklift Parts, Hyster Forklift Parts, Yale Forklift Parts, Baker-Linde Forklift Parts, Intrupa Forklift Parts, Clark Lift Truck Parts, Caterpillar Lift Truck Parts, Hyster Lift Truck Par - Bill is topnotch and I highly recommend them for any LPG parts!
First, I utilized the bottom portion of my 2F aircleaner assembly to mount the Model E and lockoff. I simply drilled two holes to match the mounting pattern of the evaporator and tacked two bolt from the bottom to act as "studs". I cut off the "intake portion of the aircleaner to make room for the vapor hose to run from the evaporator to the mixer.
Next came plumbing the evaporator. You simply have to tap the supply and return lines from the heater with supplied Y-Pipes. They can be seen here:
Supply:
Return:
You have to make sure to install the y-pipes in the same orientation so that one is pumping coolant to the evaporator and the other is sucking it out and back to the radiator. This warms the Model E to help convert the LPG to vapor form.
I connected the high pressure hose to the lockoff and routed it directly down the firewall on the passenger side of the transmission and up into the cap where the fuel supply and return hoses originally were located:
The tanks are to be mounted in the rear, one on each fender well - brackets are on order and I'll update the thread once I have them installed.
Next was fitting the Offy intake. I am running 3FE exhaust manifolds, because the 6-1 header I ran for years never seemed to make a good seal. I had to rework the mounting surfaces to make sure the flange thickness was identical between the intake and exhaust manifolds. I simply used a dial caliper and filed the aluminum intake until each bolt location had matching thicknesses. I also used copper washers on the studs in the center locations to add some forgiveness since the copper molds when you torque the nuts down good. They can be seen in the picture below (barely), but the next picture is more to show the bracket I fabbed to maintain the stock throttle linkage:
The Holley four barrel base plate bolts directly to the Impco 425 and the Offy intake. It utilizes vacuum secondaries, which apparently won't work with LPG, so I tied the secondary linkage to the primary using a machine screw and nut. You can use this to adjust how far in the throttle cycle the sencodaries open, which I have moved since this picture:
I wasn't sure if it was necessary, but I filled the vacuum ports on the baseplate with JB Weld and sanded smooth. I believe the key is to close up the hole in the center of the plate, but I knew the other ports weren't utilized with the LPG mixer, so I filled them as well. I left one vacuum port open, which is to be utilized for dizzy vacuum advance:
Next issue was getting the throttle linkage to work with the Holley plate. I looked at getting a cable pedal setup, but decided that was more trouble and an extra $150 - plus I think the stock linkage is a good setup. So I had to manipulate the linkages to fit the Holley throttle linkage location. I had to shorten the throw rod that goes from the firewall bracket to the carb. I fabricated an L bracket to mount the throw rod and it can be seen in the photo above I included to show the copper washers. I also had to cut and reweld the bracket that mounts to the firewall about 1 inch towards the passenger side to get the linakges to match up. I robbed the linkage ball joint from my Weber that mates with the Toyota linkage and mounted it to the Holley arm. I also had to trim the Holley baseplate arm because it was hitting the brake booseter. A few pics of the linkage mods:
Next I just had to mount the 425 to the Holley baseplate. For this, I couldn't find the exact right gasket, so I used a generic Holley baseplate gasket and trimmed it to fit the 425 (between the mixer and baseplate).
The next issue I had was the aircleaner. The Impco 425 has a 5 1/8" diameter neck, so most Holley open air element assemblies will work. However, given the close proximity of the mixer to the brake booster, there is no room for that style. Therefore, I found this "trick" Spectre 9841 Carb Hat/Plenum. It was about $80, but it's the best I could come up with that would fit in the space left. I used a Spectre open air intake element I got on the ricer isle at Autozone for $25. One issue was the valve cover vent connection. I drilled and tapped the plenum to accept a brass NPT 5/8" hose barb and sealed it with some silicone:
The last issue was getting manifold vacuum for the PCV. The Offy I got had a huge threaded port on the side that was tapped for 3/4" fine threads. I couldn't find any manifold union to fit that port, so I had to make one. I center drilled a 3/4" bolt and tapped it for a 1/8" NPT hose barb:
Ramon
Just finished up my LPG conversion on my '78 FJ40. I am sure some of you have seen some threads I have posted for help, but I thought I'd start my writeup. I still have some tuning to do since I am getting horrible mileage - I think I really need to get my dizzy recurved and I have to get an AFR setup to find out where I am on mixture. I'll add that to this writeup as I get that done.
My main concern was that I was getting some carb stumble out of my 38/38 Weber, which had previously served me really well. I never could seem to get the mixture right and since my Cruiser "Dozer", is mostly a trailer queen, I decided an LPG conversion was a good option. I looked at doing the 2FE, but have domed pistons so I scrapped that idea.
I started off by buying a "kit" from a fellow Mud member. It included an Impco 425 mixer, Model E evaporator, vacuum lockoff, fuel pump blockoff plate, heater hose taps, vapor hose, and a Offenhauser dual-plane intake, as well as a Holley (650?) vacuum secondary throttle plate. I picked this up for $400 and added the high pressure hose for $68 from Nash Lift Truck Supply Co. - Clark Forklift Parts, Caterpillar Forklift Parts, Hyster Forklift Parts, Yale Forklift Parts, Baker-Linde Forklift Parts, Intrupa Forklift Parts, Clark Lift Truck Parts, Caterpillar Lift Truck Parts, Hyster Lift Truck Par - Bill is topnotch and I highly recommend them for any LPG parts!
First, I utilized the bottom portion of my 2F aircleaner assembly to mount the Model E and lockoff. I simply drilled two holes to match the mounting pattern of the evaporator and tacked two bolt from the bottom to act as "studs". I cut off the "intake portion of the aircleaner to make room for the vapor hose to run from the evaporator to the mixer.
Next came plumbing the evaporator. You simply have to tap the supply and return lines from the heater with supplied Y-Pipes. They can be seen here:
Supply:
Return:
You have to make sure to install the y-pipes in the same orientation so that one is pumping coolant to the evaporator and the other is sucking it out and back to the radiator. This warms the Model E to help convert the LPG to vapor form.
I connected the high pressure hose to the lockoff and routed it directly down the firewall on the passenger side of the transmission and up into the cap where the fuel supply and return hoses originally were located:
The tanks are to be mounted in the rear, one on each fender well - brackets are on order and I'll update the thread once I have them installed.
Next was fitting the Offy intake. I am running 3FE exhaust manifolds, because the 6-1 header I ran for years never seemed to make a good seal. I had to rework the mounting surfaces to make sure the flange thickness was identical between the intake and exhaust manifolds. I simply used a dial caliper and filed the aluminum intake until each bolt location had matching thicknesses. I also used copper washers on the studs in the center locations to add some forgiveness since the copper molds when you torque the nuts down good. They can be seen in the picture below (barely), but the next picture is more to show the bracket I fabbed to maintain the stock throttle linkage:
The Holley four barrel base plate bolts directly to the Impco 425 and the Offy intake. It utilizes vacuum secondaries, which apparently won't work with LPG, so I tied the secondary linkage to the primary using a machine screw and nut. You can use this to adjust how far in the throttle cycle the sencodaries open, which I have moved since this picture:
I wasn't sure if it was necessary, but I filled the vacuum ports on the baseplate with JB Weld and sanded smooth. I believe the key is to close up the hole in the center of the plate, but I knew the other ports weren't utilized with the LPG mixer, so I filled them as well. I left one vacuum port open, which is to be utilized for dizzy vacuum advance:
Next issue was getting the throttle linkage to work with the Holley plate. I looked at getting a cable pedal setup, but decided that was more trouble and an extra $150 - plus I think the stock linkage is a good setup. So I had to manipulate the linkages to fit the Holley throttle linkage location. I had to shorten the throw rod that goes from the firewall bracket to the carb. I fabricated an L bracket to mount the throw rod and it can be seen in the photo above I included to show the copper washers. I also had to cut and reweld the bracket that mounts to the firewall about 1 inch towards the passenger side to get the linakges to match up. I robbed the linkage ball joint from my Weber that mates with the Toyota linkage and mounted it to the Holley arm. I also had to trim the Holley baseplate arm because it was hitting the brake booseter. A few pics of the linkage mods:
Next I just had to mount the 425 to the Holley baseplate. For this, I couldn't find the exact right gasket, so I used a generic Holley baseplate gasket and trimmed it to fit the 425 (between the mixer and baseplate).
The next issue I had was the aircleaner. The Impco 425 has a 5 1/8" diameter neck, so most Holley open air element assemblies will work. However, given the close proximity of the mixer to the brake booster, there is no room for that style. Therefore, I found this "trick" Spectre 9841 Carb Hat/Plenum. It was about $80, but it's the best I could come up with that would fit in the space left. I used a Spectre open air intake element I got on the ricer isle at Autozone for $25. One issue was the valve cover vent connection. I drilled and tapped the plenum to accept a brass NPT 5/8" hose barb and sealed it with some silicone:
The last issue was getting manifold vacuum for the PCV. The Offy I got had a huge threaded port on the side that was tapped for 3/4" fine threads. I couldn't find any manifold union to fit that port, so I had to make one. I center drilled a 3/4" bolt and tapped it for a 1/8" NPT hose barb:
Ramon
