engine swap

[datsun77]

i recently bought a 720 with out an engine with an automatic trans.i have a 79 620 parts truck with a good motor and 4sp trans.would this be a direct fit in the 720?and does anybody know if i can use the automatic trans or if the clutch and brake pedals will work out of my 620 in the 720.any imput would be appreciated thanks!!

[datsunaholic]

1) The engine and tranny will swap in, but the pedals probably won't (and you'll need to plumb in clutch lines). The speedometer won't have the idle kick-down switch in it, though (but if you aren't using the stock Hitachi carb it won't matter).

 

2) You can use the automatic, but you'll need a flexplate and spacer (and likely the torque converter if you didn't get that).

[datzenmike]

If its an '80 720 the L20B will slip right in and fit the automatic, but like 'aholic said you need the flexplate and crank spacer. If it's an '81 or older you will need another Z series motor to fit that automatic.

[datsun77]

thanks for the info.does anyone know which engine mounts i will need to use and will the starter work with the 720 trans since it bolts up at the top instead of the bottom thanks!

[datzenmike]

What year is the 720????

 

Two different series motors were used in the 720 line. The first year, '80, the old L20B was used, same as your '79 620. But starting in '81 Z series motors were used which sit more upright than the L series. Transmission bolt patterns reflect this 'tilt and so the motors aren't really swappable between different series.

[datsun77]

the truck is an 85 which came with the z24s engine and the hf38 rear axle.iwill ditch the auto idea if i can use the motor and manual trans but if it wont work. has anyone put a 720 bed on a 620 or swaped in the 720 rear axle on a 620. does anyone know the axle ratio for this truck?

[datzenmike]

You already have told me the differential size. The 38 in HF38 means 3.889 This is the usual rear axle ratio for the automatic truck. The carrier is an H-190A

 

The carrier will most likely swap into the 620 axle but not advised. The 620 uses a 4.11 ratio and dropping it to 3.889 will make it very sluggish.