chaseincats

My friend has a '75 280 that had a crane x700 spark box on it which we removed. After reconnecting the stock ignition system we noticed the ballast resistor had been removed by the PO. Using the 12v coil the crane module used, would connecting both power wires to the positive terminal cause any long-term damage to the stock transistor ignition module? The car runs when wired that way. If running it that way will cause an eventual issue on a '75, what did Datsun do to the '78 model since that was the only year that didn't use the ballast resistor?

Ran the car without a thermostat and it got up to the temp it gets with the thermostat in it (albeit took a lot longer to get there of course). I also had the block/radiator power flushed and not much rust came out which either means its REALLY clumped up in there or I got it all out flushing it a few times.

Does anyone know where/if you can buy the reluctor wheel for a 280z distributor? We tried to take the one out of a broken distributor to fit a working on and ruined the teeth.

Definitely a fair point but I grabbed an IR temp gun and verified that the engine temp was fluctuating and not a goofy gauge 😞

Alright, I'll give that a shot. Again, it's not about being precise or 'that's a fine temperature.' The car is running differently than it was before which is indicating there is an issue. The fact that it is not bad yet doesn't mean the issue should be ignored. The difference isn't only the temperature it's getting to - the main difference is the temperature flux between idling at a stop light and driving with air through the radiator. Before this issue started in 2020, the needle got to 170 and never moved regardless of idling at a stoplight or not.

It’s not a boiling issue (at least not yet), the issue is that it isn’t behaving like it was last year when this issue started which tells me something is wrong and will eventually get worse.

It might go a bit below 170. Even though 185 to 190 isn’t a huge issue (arguably an issue at all), the fact that it used to get to 170 and sit there regardless of if I’m idling or driving freeway speed means something is not working as it was/should, you know?

As long as I've owned the car it was never full because the old radiator had a pinhole leak at the top and didn't hold pressure but always kept the car at 170. The new radiator is filled to the brim but not the reservoir tank. If the car's problem was the head gasket though, wouldn't it run warm all the time regardless of airflow through the radiator?

Gotcha. I will be out of town so I can try this in a few weeks. The reason I was trying to go around this is paper gaskets do not seal my thermostat housing - each time I pop it open I need to seal it with RTV. Regarding head gaskets, one thing I don't understand is if I accelerate hard and shift, there will be a puff of white/sweet smelling smoke out of the tailpipe (coolant) but when I pressurized the cylinders for the leak-down test, there weren't any bubbles in the radiator. Also the exhaust gas in the radiator tester with the blue liquid did not change colors either. I don't understand how coolant makes its way into the cylinders sometimes but does not show up in any tests.

Just so I understand, what would it running better without a thermostat or running worse tell us?

With the old smaller thermostat the car would get up to 180+ at idling but when starting from a stop (at a traffic light for example), the car would drop back down to 170 after a few minutes of air flowing through the radiator at road speeds. With the new larger opening thermostat, it will get up to 180+ at idle but when starting from a stop with this new thermostat, the car drops to 170 within a matter of seconds - the car is cooled way faster with the larger OEM thermostat. I have not driven the car without a thermostat because the car never had this problem with the old OEM thermostat (until 2020). The new OEM thermostat that's in the car now was tested in a pot of water so I could confirm it was working as it should and at the proper temperatures before installing in the car. Driving the car without a thermostat might keep it slightly cooler but that would be a bandaide and not fix the real problem.

We won't need to wait for spring, the thermostat didn't do anything different except drop the temperature noticeably faster when going from 180+ at idle down to 170 when driving. I did notice that when I held the idle higher than 800, the temp would drop slightly so I grabbed some cardboard and slowed down the fan to see if I could spin it backwards and I could a tiny bit but then it went right back to how it was supposed to run. Here's a video from just now. I replaced the old fan clutch (Aisin) with a new Aisin clutch when this started about a year ago and I believe they both worked the same way when spun backwards. So I'm assuming we're moving back to rust in the block is clogging the radiator?

I agree with no definitive answer until then. I will post some observations in the interim though.

All makes sense. Since I did a leakdown test and didn't see any bubbles in the radiator & used a combustion gas tester, how else would I check for a head gasket leak if there isn't any mayo in there either?

I did that early on after running radiator flush through the system. A good amount of stuff came out for sure. Do you think its worth doing again?

Not since I've owned it 7 years ago. I did do a leakdown test to make sure no combustion gasses were entering the coolant through the head gasket and the head gasket came back as solid. There isn't any chocolate milk under the coolant/oil caps.

Gotcha. He suggested changing back to an OEM style thermostat and if that doesn't work to knock out the back-right freeze plug (the one above the starter) and flush the engine out again through the thermostat housing. He said IF there's rust in the block, it usually sticks around near that freeze plug.

It has a brand new 3-core radiator. Everything on the cooling system was changed.

Right. The old OEM thermostat opened 20 degrees later than it should have and even at well over 200 degrees didn't fully open. The aftermarket one reacted more along the lines of the brand new oem thermostat but it's opening isn't as large and the plunger travel isn't as far since it is physically smaller.

I did not. I felt that since the car will have a thermostat regardless, testing one to confirm it works as advertised before putting it in would negate that test especially since I confirmed the original OEM one was broken and the newer aftermarket one is more-or-less defective by design.

UPDATE: I spoke with my old Z mechanic to see where he got the OEM thermostat that was in the car before my changeover to the new aftermarket one earlier this year since OEM ones are supposedly NLA. It turns out Nissan still makes a thermostat that works but is not the original one designated for the car. This thermostat is a Nissan part (part number 21200-F3190) but works in a bunch of their engines (L-series included). This is the thermostat that held the car's temperature at 170 from 2015-2020 before I started having cooling issues. I threw the old and new OEM thermostats as well as the aftermarket one in a pot of water. The old OEM thermostat started opening at 185 (unlike the new OEM one which opened around 170) and after continuing to heat the pot, the old OEM thermostat only ended up opening about 2/3's as much as the new OEM thermostat so the old OEM thermostat was indeed bad. The aftermarket one opened and closed at the same temperatures as the new OEM thermostat but the opening indeed is about 30% smaller than the OEM thermostat and the amount of travel the plunger can physically move is again maybe 30% less due to it being physically shorter. I have not tried the new thermostat in the car because driving it around in this cold weather won't give me a definitive answer, but I am feeling confident that my old worn-out OEM thermostat not opening at the right temperature (and not to the right amount) started this issue, and installing an aftermarket thermostat that physically can't move as much coolant as an OEM one kept me heating up, but for for a different reason entirely. With the new OEM thermostat correcting both issues, we should be all set come spring time. Here are pictures of the OEM one (right side) next to the aftermarket one (left side). You can see the opening is considerably smaller and plunger's travel is considerably shorter on the aftermarket unit. I will update you guys in the spring. I don't understand how/why they sell this design...

I've been asking in a variety of ways if the spacer is needed to have the gap between the body and tire identical on the front or rear. I haven't received a yes or no yet.

Oh, so the spacer would be necessary for the car's rear not to sag then it seems?

I haven't actually. That said, I have the considerably lighter (23 lbs) 77/78 bumpers so I don't think it would change the ride height as much as it would have with the 74-76 ones which were ~90 lbs each.

Any idea without the spacer, would the vehicle sit level with the ground or would the rear sag compared to the front?