Making the Z24 alright

[captain720]

Ok guys so I haven't been super active lately because I have honestly been putting all my spare time into keeping my dailys on the road and my 87 D21 lost its Z24 due to rod bearing failure from the last owner and I need to put her back on the road so I can finish the white truck and get Charlie his parts and blah blah blah. 

 

Anyways to the point here D21 needs a new Z24 and I have a whole bunch of Z24s that I got basically free out if various parts trucks and what not. So I have a good head and good block and crank and rods and all that junk sorted out and I AM NOT PUTTING IN A KA OK!?! I know we have shut down a lot of noobs trying to hot rod the Z24 but I just want to do a couple things here to increase power while I have it all torn down.

So I am going to clean up the valves and intake manifold to remove burs and slightly increase flow, finds some pistons to bump compression to around 9.1-9.5 and run a slightly reground cam ditch the D21 throttle body for a spare 32/36 that I have (I have a spare) and a stage 2 clutch, Doug thorley (I know it "does nothing" but it looks cool). Now do not say it's going to be cheaper to put in a ka because I have all these parts already and they we're all basically free. All I need is the cam ($125 or so with core) and pistons from something. Just looking for suggestions and input I think Mike has done some work on the Z24 head and just looking for input. Also planning on a KA oil pump.

 

If I pick up 15 numbers each way that would be way more than enough to make me happy

 

 

Thanks in advance

[captain720]

Also just so no one yells at me I am gonna run a pre 1986.5 distributor

[datzenmike]

Use KA24E pistons. They have the same pin height and diameter as the stock Z24 pistons but hardly any dish. KA24E pistons will make 9.52 compression. I would over bore the Z24 and get 1mm oversixe to maximaze the engine displacement.

 

The D21 fuel pump is high pressure and won't work on a carb.

 

Any Z24 distributor should work fine.

 

Not too sure the Weber or Z24 carb will fit the EFI intake. You may need to use a carb intake.

[captain720]

Yeah I just keeps the intakes and carbs together when I part out a truck, keeps the adapter plate from warping thanks for the heads up in ka pistons will plan on that now. Local machine shop will handle block. Will the ka pistons still work with oversize?

Edited October 11, 2018 by captain720

[Charlie69]

You do not want any more engine problems obviously.

 

You should have quite a pile of 720 Parts now!  LOL

 

I am in the process of buying an 84 parts truck.  I believe it has AC not sure as I have not seen the truck in person.

[datzenmike]

 Get the KA24E pistons and rings in the oversize you want. THEN send them and the block out to be over bored. A good machinist will measure the pistons (none are absolutely and exactly perfect) and bore to match them. He will also hone the bores to get the perfect piston / wall clearance and finish. Or he should.  

[bottomwatcher]

The z24 is a very reliable motor and the power is not that bad as long as it isn't tired and you are not trying to swing larger than stock tires. if you are trying to swing big tires well it will be a dog and not amount bolts ons  will help.

[captain720]

19 minutes ago, bottomwatcher said:

The z24 is a very reliable motor and the power is not that bad as long as it isn't tired and you are not trying to swing larger than stock tires. if you are trying to swing big tires well it will be a dog and not amount bolts ons  will help.

I know I have been driving the Z24 in various rigs and combinations for the past couple years and I love it! As I am assembling my next one though I am just trying to make the best Z24 I can because I like it's reliability and it really isn't that slow to begin with.

[datzenmike]

1 hour ago, bottomwatcher said:

The z24 is a very reliable motor and the power is not that bad as long as it isn't tired and you are not trying to swing larger than stock tires. if you are trying to swing big tires well it will be a dog and not amount bolts ons  will help.

 

This is the abominable gearing used on a heavy truck to try and drag the most mileage from a high torque engine. It should not be below 4.11 and 4.375 would be even better.

[Charlie69]

My 720 2 wd king cab 5 speed runs great with the 370 gear ratio.  Pulling a double axle enclosed U haul trailer full of Datsun/Nissan parts from Battle Mountain NV did work it a little.  10 miles an per hour up the grades but she never missed a lick.  On the flat stretches I would find myself doing 85/90 miles per hour.  I do not pull heavy loads that much so the 370s are just fine.