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.