EEC_1981 Posted May 18, 2015 Report Share Posted May 18, 2015 Hey Im new to this site and I need some info please. I have a 77 620 with an l20b and a five speed and I need to know if I can swap it into an 83 king cab 2wd that i recently just got. It had a z24 with a 5speed but both the motor and tranny are shot but the truck is real nice and worth saving my 620 on the other hand has a good motor and tranny but the body is shot and rusted out. Anyhow it looks close but the motor mounts look different any info would be appreciated thank you Quote Link to comment
datzenmike Posted May 19, 2015 Report Share Posted May 19, 2015 I have put a Z24 into a 620 so an L20B should go into a 720. You will need to check the transmission length. The 720 transmission will have to be 31.5" long, same as the 620. The engine brackets and probably the rubber isolators on the 620 will have to be used on the 720 frame to mount it. You may have to use the 720 rubber isolators. You may have to mix and match but the brackets on the L20B stay with the engine. The throttle cable on the 620 is much shorter and you probably will have to use the 620 cable and modify how it is bolted on to the fire wall. The 620 exhaust down pipe will be needed and have to be grafted onto the 720 pipe. The 620 rad can be used or maybe re route the top L20B hose over to the right side to match the 720 rad. Use the 720 alternator it's larger and internally regulated and your '77 alternator is not and won't work. Use your '77 coil and ballast resistor. Do not use either of the 720 coils... remove them. The 720 carb electrical plug will have a... Blue wire ... connect it to the L20B auto choke on carbRed wire..... connect it to the idle cut solenoid on carb Heater hoses on L20B are slightly differently placed but just graft them to the heater hoses on the 720 fire wall. Oil pressure sender wire is in the same location as is the reverse light switch for the transmission. Ignore the neutral and top gear switches on the 720 harness Transmission mount and drive shaft should line up fine. Clutch slave is the same. The 720 brake booster is mounted far forward and may interfere with the L20B air filter housing. You may need to get a smaller custom one for it. All I can think of right now. 1 Quote Link to comment
Lockleaf Posted May 19, 2015 Report Share Posted May 19, 2015 Mike covered most of it. The first year 720 came with an L20 in it, so the motor etc will all fit in the midst general sense. Any of the issues Mike mentioned above should be avoidable by using a few parts from that L powered 720. Those are likely available on here from other members, just ask questions as you encounter issues and use the classifieds when necessary. Quote Link to comment
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