akorna

New listing: 1974 Datsun 260z 2+2 2nd owner - rare

If you are interested - this is a decent car - not too may 2+2's survived. 1974 Datsun 260z 2+2 2nd owner - nice

All - thanks for the advice and observations. I re-assembled the entire intake and exhaust manifolds using new gaskets, pcv valve, pcv hose, and thin beads of copper silicone sealant. While I had the exhaust manifolds off, I removed all of the air injection plumbing, and blocked off the holes with 14mm X 1.25 bolts (installed bolts with sealant, then cut off bolt heads and ground close to flush with the manifold. I also replaced the exhaust manifold to exhaust pipe gasket. The exisiting one pretty much crumbled apart during disassembly. I had two studs fail, the far forward exhaust stud (enough thread left that I was able to double nut and drown in PB blaster and remove) and the far rear (had to drill and insert). I baselined the car settings and let the sealant cure for 24 hours. On restart, it fired up quicker than I expected. I slowly released the choke, and was able to get it to idle pretty well at about 1000 rpm - much smoother than before. I was pleased to see that vacuum was now 18-19 inches of mercury, instead of the 10-12 earlier. I synchronized the carbs, left the mixture alone for the moment and test drove - seemed much better. This coming weekend I will set mixture and check for any evidence of coolant loss, but I'm pretty sure the head is fine. Likely the coolant got in the intake during disassembly. Attached are before and after pics. Before After

Thanks Nissanman/Bobc, Note that the vacuum leak was at the #4 Intake, the coolant was visible in the #3. I did not drain the radiator, but rather removed carbs, then disconnected the hoses at each intake - so there is a chance that it leaked back into the head. I think I'll go ahead intall a new Intake/Exhaust gasket w/new hardware and re-assmble everything and post what happens.

I have been troubleshooting a recent rough idle and hesitation. Everything checked out fine, but vacuum was only about 10-12 Hg at idle. I tracked down an intake leak at the head at the #4 cylinder. Knew I had to replace the intake/exhaust gasket, so removed everything. After I had the intake manifolds off, I could see in the head that the valve (closed) was in a pool of coolant! I have 175 psi compression in that cylinder and no sign of coolant in the oil, or oil in the coolant. The plug had looked like the mixture was running a little lean, but similar to the other plugs. The engine has not had white smoke coming out the exhaust. I wonder if the coolant leaked in from the manifold ('72 w/water cooled three screw Ztherapy SU's) during disassembly or am I looking at a cracked head? Anyone experience something similar?

I have had no problems with the Pertronix Ignitor since the install chronicled in this post Regarding the dwell - when I set my points to the factory specs (0.016-0.020), I would get about a 24-28 degree dwell. In order to get to the factory spec of 35 degrees, I would have to go with a gap of 0.012-0.014. I noted when installing the Pertronix that the dwell was the same as with the factory spec gap - about 24-28 degrees.

Crazy, Your compression looks fairly even, but on the low side, but car should still run. You've mentioned in recent posts that you were setting the floats, but you described adjusting the mixture, by turning the mixture screws. Did you ever actually remove the float bowl lids and set the floats? Virtually all of the plugs show fuel fouling due to flooding or an overly rich mixture. You mentioned that you no longer have choke cables - so how are you starting/running the car without a choke? If you're just lowering the nozzles then the mixture will be way too rich. Small vacuum leaks around the throttle shafts will tend to cause a lean mixture, not a rich one. With the car dying suddenly, you have something interupting fuel flow or spark. I really don't think your carbs are bad, since there are short periods that the car will run OK from your description.

Others can chime in here on the numbers - but the compression seem to be pretty low, which would impact combustion - I would think you should be looking for something in the 150-170 psi range. I assume these were obtained using a "dry test" - you could follow-up with a "wet" test by squirting a few shots of engine oil into each cylinder and re-testing. If the compression goes up more than a couple PSI then your rings/pistons/cylinder walls are worn. If it does not, then you have a head gasket or valve train issue. If your static timing is off, then the valves could be opening at the wrong time and compression may be reduced.

The white smoke leads me to head gasket leak - but also think you need to test the compression of all the cylinders. Why do you think that removal of the emissions gear would make it harder to start? Are some of the hoses/fittings not capped or plugged? If your dizzy is more than 15 years old than the breaker plate is probably sticking and you are only getting mechanical advance. Do you have a mechanical fuel pump? Is it reading between 3-4 psi? Is the tank full of FRESH gas?

Thanks all for the feedback. At one point I removed the strut, dovetails, and latch - issue still there. I also saw some puctures of a 280z with two struts that displayed the same alignment problem (of course the right strut could have been bad for years...). It's possible the strut may have caused the deformation over the years, or maybe it's just a panel stamping problem.

I noticed on my 72 Z and in photos of other Z's that the bottom left corner of the hatch is higher than the corner of the rear quarter panel (is not flush) - I'm not sure if this is related to the single strut support or some other issue. Anybody address and correct this?

Fascinating - no wonder folks go to the 280ZX distributor upgrade.

Motorman7, The cam adjustment screw is just for setting the points. Pertronix could have made the hole larger so you didn't have to touch it at all. My green tape was very close to the Ignitor, probably 0.015-0.018 - and you're right, slotting the lower fixed hole would be the solution - might be another source of unsucessfull installations. Did you get your ignitor replaced, or are you running w/out the tape? Ditto your observation on the wiring orientation - scratched my head on that one too I'm an engineer also - I feel your pain.

tlorber, So I would add to 5 that the front to rear inclination would effect the adjustment? - I would think it would have to be on a pretty severe slope.

This may be repetitive - but I've spent a lot of time researching and playing with the SU/Hitachi carbs – in my case three screw round tops. Here are some statements mostly about mixture that I’d like some feedback on - I think are all true, but please correct me if I’m wrong. 1. The rough setting for fuel mixture is the float level. 2. The fine setting for fuel mixture is the nozzle height adjustment screw. 3. The fuel level in the float bowl needs to be high enough to ensure adequate fuel supply at full load, but low enough to ensure that flooding will not occur. (approx. 23mm from the top of the float bowl) 4. If the fuel level is at the lower end of the acceptable range, then more counter-clockwise turns (lowering of the nozzle) of the mixture screw will be required to reach optimum mixture strength. A higher fuel level will require fewer counter-clockwise turns (lowering of the nozzle). 5. The number of counter-clockwise turns of the nut to reach optimum mixture is dependent on temperature and elevation. Lower elevation increases turn requirement, lower temperature increases turn requirements. Typical range is 1 to 4 turns. 6. One turn of the mixture adjusting screw moves the nozzle approximately 1 mm. 7. If the front and rear carburetor float levels are different, then the number of turns for optimum mixture will be different for each carb. 8. The front carb primarily feeds cyls 1, 2, 3, and the rear 4, 5, and 6. However, the balance tube reduces the direct relationship and the fuel mixture to the cylinders is more of an average of the two carburetor settings.

Mikez73, I considered the 280zx dizzy route, but from a cost (initial and component replacement) I decided to go this route. The remanufactured dizzy was $55 from Autozone, the Pertronix Ignitor was $69 - so I had a "new" dizzy for $124 that I could convert back to points if needed. Some folks still have some luck using a salvage yard 280zx dizzy, but I didn't want to replace a 38 year old electrical/mechanical part with a 29 year old one. The car is performing better overall - but yes, the faster start is a big improvement for me.

Decided to go for the Pertronix Ignitor after installing a remanufactured stock dizzy from Autozone. I had all new ignition components now, so the baseline would be a properly functioning point system. There was also some debate on the correct/best coil to use with the Ignitor – a 1.5 Ohm with external 1.6 Ohm resistor, or a 3.0 Ohm coil without a resistor. The factory set-up uses the external resistor that is bypassed during starting to deliver higher voltage to the coil/points and through the external resistor while running to protect the points/coil. Many folks have gone through this, but I thought I'd go through my install as shown in pics below: The Ignitor 1761 only has a five parts – the unit with leads, the cylinder that fits over the dizzy shaft (DO NOT REMOVE THE GREEN TAPE), and three screws. 1. The leads are too short to reach the coil/resistor in the stock location – you will need to cut off the ring terminals and add 8-12 inches of wire. The instructions say to use 20 awg wire – I had some 16 awg in black and red, and spiced the additional wire by soldering the joints and sealing with heat shrink tubing. I used female quick disconnects with shrink tubing to match the factory connections. 2. Before installing I would start the car and warm it up a little bit – not so hot as to burn you as you work, but enough to make sure everything is operating, and the car does not have any unexpected no/poor start problems. 3. You do not need to align the dizzy to TDC or anything like that – just pop the cap and go to work. Remove the points assembly and the plastic insert in the cut-out that connects the black (-) wire from the coil and the condenser to the points. The condenser is not needed for the Ignitor, but I left it attached in case I wanted to return to the points set up for any reason. The wire to the coil is disconnected also, but not removed for the same reason. 4. Install the Ignitor just like a set of points – you may have to rotate the adjusting screw on the breaker plate so that the two attaching screw holes align. Then reconnect the distributor ground wire with the slotted screw. IMPORTANT: The slotted screw provided is too long – if you do not add washers (none provided in the kit) it will interfere with the operation of the breaker plate vacuum advance – I made this mistake and it resulted in a poor start/poor running situation. This may be a problem others experienced with the Ignitor, but did not realize it. 5. Route the wires out through the dizzy body cut-out and make sure that it they will not contact the rotor or shaft. Press in the rubber grommet so it fits snugly. 6. Align the black cylinder over the shaft cam and carefully press down on the shaft – if you aligned in properly you will hear/feel it seat. Once in place it should almost be touching the ignitor. If it is touching, something is wrong with the install, or the dizzy is worn excessively. 7. At this point I would check the operation of the vacuum advance with a hand held vacuum pump to make sure there is no problem as noted in step 3. The advance should start moving the breaker plate at 4-5 in Hg, and smoothly return when the vacuum is released. 8. INSTALL THE ROTOR – the Ignitor just replaces the points and condenser. Make sure that wires will are not touching the rotor. 9. Install the cap. Make sure you are not pinching any of the Ignitor wires. 10. If you are using the stock coil and resistor, connect the Ignitor RED wire to the ignition input side of the resistor (Black/White wire) using your connector of choice. You will now have the red and black/wire connected to the rear terminal of the 1.6 Ohm resistor. 11. Connect the Ignitor black wire to the (-) side of the coil and you should be good to go. 12. Cross your fingers and attempt to start the car as you normally would. If the engine doesn’t start, re-check all of your connections. 13. Assuming the engine is now running, you should check your timing with a timing light, you will probably have to adjust it. You may also have to adjust carbs, open spark plug gap and other tweaks to take full advantage of the ignitor. A TALE OF TWO COILS: I bought two coils to test for my Ignitor install – the Pertronix 40511, 3.0 Ohm that the manufacturer recommends (bypass the stock resistor) and the 40011, 1.5 Ohm for use with the resistor. I used the 1.5 Ohm/Resistor set-up first with the Pertronix. Subjectively, I did not sense a dramatic change in cold start/hot start, idle and acceleration over my refreshed point system (I had already tested the point system with the 1.5 Ohm coil with a fresh 1.6 Ohm resistor and did see some improvement over the apparently tired Bosch RED coil). I swapped the in the 3.0 coil w/out the resistor. I did a cold start this morning – this is a way I’ve been monitoring progress; how many 5 second attempts it takes to start (when I first got the car in December, it took 10 or more attempts to start!) – and at 36 degrees it coughed on the second attempt and started on the third. About eight hours later this evening at 44 degrees, it started in on the first attempt. All attempts were with full choke applied. The next day, temp at 42 degrees, it again started on the first attempt. I noted a more consistent idle and smoother acceleration - not dramatic, but noticeable. The tachometer worked fine with the 3.0 Ohm Coil. Overall, the 3.0 coil seemed to work at least as well as the 1.5 Ohm coil w/resistor, perhaps a little better – maybe the tech folks at Pertronix knew what they were talking about. Here is the final wiring diagram.

alhbln, Thanks for the specs on the Bosch coil. Interestingly enough I replaced the bosch coil with a Pertronix 1.5 OHM coil 40011 and the resistor with a generic 1.5 Ohm from Summit and the car showed an improvement in cold starting and idle stability - actually got the car to start on the second try at 40 degrees. I'll detail more of this in another thread on the Pertronix ignitor and the 1.5 ohm coil w/resistor vs the 3.0 coil w/out resistor.

alhbln, The heavy gauge black or black/white wire goes from the ignition to the resistor. Inserting a relay there would not influence the tach operation.

On the issue of low voltage to the coil - when I measured system voltages I found that with the engine off and ignition in run - there was about a 0.7v loss through the ignition switch to the resistor (black wire). Not a huge drop, but you could install a relay go direct from the battery - would also reduce current on the ignition switch - right?

Sorry for being ignorant but what is "atm" Also - I just solved a problem w/my distributor - I thought the breaker plate was ok - but in fact it was sticking/catching. If you have a hand vacuum pump, recheck your vacuum advance operation - it should start operating at 4-5 inches Hg - not 8-10 (see the FSM) If your vacuum advance is not even connected, not sure that would be an issue - but I would proceed w/the installation of the port and connect the vacuum. Another diagnostic thought - have you checked compression?

jwgarvey, The coil is a Bosch Red Super Coil - I have not been able to find the spec for it- I was expecting something along the lines of 10.6 or higher, but the temp was around 40 degrees, so that would have reduced the resistance slightly.

Are you sure your carbs are not running too rich? You may also have a sticking nozzle that does not move properly up into the carb after releasing the choke. After the car has warmed up, release the choke and then push up on the nozzle under the carb for each carb. If it moves at all the nozzle/choke mechanism is sticking. Why is your vacuum advance disconnected?

Thanks for the feedback - doesn't sound like anything conclusive at this point regarding the coil selection. I may experiment with this since I just installed a rebuilt distriutor due to a bad breaker plate - so I know that the shaft, vacuum and centrifugal advance is all working OK.