NapZ in my '64 320

[LKPar1270]

I haven't been on here in a while.  The Puddle Jumper has been on the road for a couple of weeks, some problems have been cropping up, mainly the alternator, using a Chevy geo alternator, put the 3rd one on Thursday, I like these but don't use a rebuilt, get new.  Right now I cant get my aftermarket tachometer to work correctly.  I'm running an '89 NapZ with an '80 distributor, wired as if it were Kettering ignition.  Maybe this is my problem as I see in a wiring diagram of the '86 d21, the is some sort of 'power resistor' on the coils and a condenser between the two coils.  Any suggestions on what parts I need to duplicate this?

Edited March 13, 2021 by LKPar1270

[datzenmike]

The tach should run off the negative side of the intake coil.

 

'80 distributor? Are you not running dual spark plugs?????

[LKPar1270]

That's just how I have been hooking them up, I get a reading that looks like it may be close to correct if you average the reading, but it is constantly wandering high and low, sometimes it goes full scale for a few seconds, and sometimes 0.  Doesnt make sense to me, but then I have never dealt with duel ignition like this before.

[datzenmike]

Are you running dual coils? Because you said you have an '80 distributor and that are for single plug L series engines that year.

 

I'll assume it's  Z series distributor with 8 plug wires. Dual plugs are the same as single just two of them. The two coils both fire together so either coil negative will work but the intake is the better one as under certain conditions the exhaust coil can be turned off.

 

 

[LKPar1270]

That's just how I have been hooking them up, I get a reading that looks like it may be close to correct if you average the reading, but it is constantly wandering high and low, sometimes it goes full scale for a few seconds, and sometimes 0.  Doesnt make sense to me, but then I have never dealt with duel ignition like this before.

That '80 distributor was a misprint, it's a 1986 distributor, dual coil  - 8 plugs.

[LKPar1270]

It's an'86 distributor, dual coil  - 8 plugs 

[datzenmike]

The tach on the 80s cars and trucks had a 2.2K ohm resistor in line. If you have a 720 harness (I doubt) this resistor may be messing with the after market tach. If you wired it yourself to one of the coil negative terminals... it should work.

 

Do you have a good ground from the block to the body sheet metal??? Or battery negative to the sheet metal body? Assume it is negative ground?

[LKPar1270]

Yes, I do my own wiring, infact I do everything myself, and have good ground between block and body.  This has got me stumped.  That is why I was wondering if there was something about this distributor and the 'power resistor ' on the intake coil and the condenser between the coils shown on the d21 wiring diagrams.

[datzenmike]

The D21 coils look like a small transformer with a power transistor on the side right? Those are used with the crank angle sensor distributor set up on the Z24i engines. 

 

Borrow a couple of coils that the distributor is used to working with and set those other ones aside.

[LKPar1270]

I'm using off the shelf, standard coils. I actually have no idea what kind of coils the '86 distributor used.  I changed the distributor from the angle sensor because I dont want fuel injection or computer control.  I guess I just assumed the older distributor could handle regular old style coils.

[LKPar1270]

I cured the problem with the tachometer.  Ive had a Holly Hyfire 6M laying around for a couple of years, decided to try it on the NapZ.  Works great, AND the tach connection works!  I do agree with all of you, it should work without the CDI, don't understand why is, and the text tachs didn't work other than I don't have the condensers or the 'power resistors' connected as it shows in the wiring diagrams for the 720s with dual ignition, that appears to be the only thing I didn't do when replacing the crank angle distributor with the 720 one.  Thanks for the input on this problem.

[LKPar1270]

I have a differincial swap question.  I know it's been talked about on here that the 320's use an h190 case.  I'm dealing with a guy now that has a 3rd member out of a 720, axel code hf38.  This guy is, I hear, a Datsun genius and he says it will exchange right into my rear end.  Any experience with this swap?

[datzenmike]

I think you will find the early trucks like the 320 have 13 spline side gears the axles fit into. Car H-190 as almost always 23 spline The 520/521 and up H-190 truck side gears are 29 spline. So there's no way a 320 axle fits a later truck H-190 differential without taking it apart and swapping the side gears. Mklotz70 has a Blue Hands video on swapping side gears. I can be done.

 

13 spline H-190 320 differential (maybe 410/411 or whatever)

 

 

23 spline H-190 car (Roadster, 510 and 810 wagons)

 

 

29 spline H-190 520/521/620/720/D21/WD21 also '83 S110 200sx and 84 S12

[LKPar1270]

Yes, I was aware I would be changing the spiders, just didnt know if the third member from a 720 actually fit my diff case.

Thanks for the info.

[datzenmike]

Side gears have the splines and yes the H-190 will fit. Yours is likely an aluminum case and from early '70? and up are steel and stronger, but heavier. The gasket is likely NLA so a good sealer like Permatex will do. It's what I used and you have to let set for 15 min. Use only GL-5 90w  oil.

[LKPar1270]

Thanks again.

[Charlie69]

12 hours ago, LKPar1270 said:

I have a differential swap question.  I know it's been talked about on here that the 320's use an h190 case.  I'm dealing with a guy now that has a 3rd member out of a 720, axle code hf38.  This guy is, I hear, a Datsun genius and he says it will exchange right into my rear end.  Any experience with this swap?

The HF38 is 3.889 ratio.  This is a real common 720 ratio and is a good ratio for highway.  On my 86 720 2wd Z24 5speed at 3500 rpm in 5 gear I am doing approximately 80 miles an hour.  My 720 will cruise all day at this speed but it actually smooths out at 85 mph.  I have this ratio in my 66 520 with a L20B automatic.  Have not driven this truck yet, I might have to go to 411 gearing which was the ratio used in the 1980 720 2wd L20B automatic.

[LKPar1270]

👍

[wayno]

Sometimes it is a pain getting the solid pin out of the 320 gear set, you have to remove the ring gear to do that, I mark the ring gear and put it back in the same place, the 720 gear sets have a roll pin which is much easier to remove.

When I have done this mod I always put the 320 gear set back together with the 720 side gears and sell them to race car guys, they like them 4.88 gears.

Fact is with a napZ engine in a 320 truck you should be able to turn 350 gears, the napZ Z24 engine has torque, but 3.8 gears should make it snappy.

[LKPar1270]

I did the swap, very happy with the hearing.  Must say though, everything I've read says it's a simple swap...Not!  Maybe the 510 3rd member is the same, but the 720 case is larger inside to account for larger spider gears.  I had to make shims out of brass to back the splined gears, 180 thousandths each side. But with that they fit nicely, no slop and smooth running.  If you have the ability to make these shims, I recommend this swap.