Looking for Info on Z24 conversion for my 74 620

[TyS]

I am looking to possibly do a Z24 conversion.... I was told it would bolt right in but I would have to shave a 1/4" of tranny shaft? Anyone who has done this conversion please fill me in on what it will take..... I have a 4 speed L18 currently in truck thats tired...

[datzenmike]

First you will need the 720 electric 3PSI fuel pump or equivalent. The Z24 does not have a mechanical fuel pump.

 

The L18 rad may be a bit small for a motor that is 1/3 larger. An L20B rad might do the trick but the Z24 rad is way too wide to fit between the 620 high beams. In any case the top inlet for the L series rad is on the left hand side and the Z24 top rad hose ia on the right so some extra bends will be needed. The Z24 plastic fan may be too large for the L18 fan shroud. If needed you can swap the L18 water pump onto the Z24. They do fit.

 

You cannot use your 4 speed for this, (as it is at least) so you will need the Z24 5 speed or any NAPS Z20 or Z22 5 speed. While we are talking transmissions, in order to fit your 620 drive shaft, your choice of transmission must be 31.5" long, the same as your current 4 speed. Some 720 5 speeds were 26" long and if this is all you have your drive shaft will need to be lengthened about 5 1/2" roughly.

 

The Z24 has the carb on the right hand side so get the much longer 720 throttle cable.

 

The Z series exhaust manifoldis much different than the L18 so you will need a custom made down pipe or part of the 720 one and weld/graft it to your exhaust system.

 

Be sure to get the dual coils from the 720 doner truck. Wiring is fairly simple for the dual plug design.

 

The Z24 alternator is a higher output (50amp) and internally regulated,* however it is a larger diameter and may rub against the 620 idler arm. You could simply just bolt your L18 alternator in and go.

 

* your L18 alternator is externally regulated so if you opt to use the 720 alt. you will need to convert your electrical system over and get rid of the voltage regulator on the pass side fender. This is not that difficult and well documented.

 

Be sure t keep and use the Z24 engine brackets. These are the metal braces that bolt directly to the sides of the block and rest against the rubber isolator mounts on the frame. Get both just in case. Your L18 brackets are vastly different and of mo use.

 

 

I swapped a Z24 into my 620 and yes it fits. Hopefully it's not from a 4X4 as the oil pan will NEVER fit. A 2wd oil pan seen to fit ok.

[TyS]

Thanks...I have a choice between an L20b and the Z24...

[datzenmike]

Then the L20B is a bolt in, but you will need the 6 bolt flywheel as well, as the L18 is 5 bolt. If the L20B is from a car, you can use the L18 oil pan and pick up on it andyou can use the L18 225mm clutch and pressure plate on it as the cars used a 200mm.

 

Have to say the Z24 has about 33% more torque than the L20B and at 2,800 RPMs, so very snappy around town.

[TasoZ24]

I have all the components necessary to do the swap just in need of wiring info... thankful for all the advice already, but have searching all day and cant find a thing besides that its well documented. Looking in the wrong places and Google just doesn't get it. Thanks for any tips :)

[datzenmike]

I put Z24 in my 620.

 

There should be three wires to the distributor. The power wire from the 620 ignition switch goes to both Z24 + sides of the coils and to power to the distributor. The coil negative wires go to the other two wires to the distributor.

[TasoZ24]

would L20B engine brackets work for this swap? My Z24 has a Z22 on passenger and L18 on driver, and not working at all. doing the lift with tractor soo trying to keep my trial/error ratio to a minimum. 

[datzenmike]

L series engine brackets will position a Z series into the L series position so... no.

[TasoZ24]

Didnt think so, thanks buddy