Captain Obvious

Off topic alert. I'm asking here because the level of experience is much higher here than where I should be asking. I just bought a cheap disposable Hyundai. It was overheated significantly by the previous owner and because of that, it needs engine work. No surprises here. I knew about all that before buying it and I got it cheap enough that even if I have to replace the engine completely, I think I did pretty well. Here's where I am... I know the head gasket has been compromised and I'm assuming that the head has warped as a result of the heat and will need to be planed flat. But before I pull it apart, I'm trying to figure out what else is wrong. I don't want to dump a bunch of money into the head only to find that the engine should just be completely yanked instead. The engine has 120K miles and the compression test numbers don't look too good. Wet looks great, but dry is below the service limit. So it sounds like rings or worn cylinders, but at 120K miles, I would be disappointed if it was just normal wear. So here's the question... Just how hot do you have to get an engine before rings lose their temper? Is it conceivable that the engine overheating episodes ruined the rings? is it conceivable that the pistons and bores are OK, and I could get out of this with just tossing new rings on the pistons?

Yes, if you've got the diode on the green, then it should protect against a grounding path. That's not what it's for, but it will do that as well. Actually the best thing would be to have diodes on both wires feeding that relay. Diode OR them together such that either of them could feed the relay without affecting the other.

And yes, it's completely conceivable that whatever shorted was far from the fuse block. For brief periods of time, copper wires can carry an enormous amount of current. Even the smaller ones.

Regarding the override wire shorting to ground in the engine bay, I don't think that would cause the issue you had, but it could be a problem. If you've got it wired as shown in the instruction sheet and the ignition switch is on, when the temp switch closes, you've got +12 on the yellow wire. And since the yellow and greens are tied together at the module, you've got +12 on the green. Shorting the green to ground would be a connection to ground through the ignition and temp switches. Also, a little unrelated, but just noticed that they have a diode on the override wire. I'd put it on the one coming from the ignition switch instead. The way they have it, you can't back power the override source from the ignition, but I think it would be more important to make sure that you can't back power the ignition from the override source. Especially if the override source is hot at all times. Did I say that right? Does that make sense?

Stumps me. I looked through the literature I've got and there's nothing even close. That's why I hadn't responded to date.

Replica Cobra. Nobody is going to take a proper one out without a surrounding of bodyguards.

Wow. Those are some nice looking front end parts! I got two other comments: First, there have been reports of snapping T/C rods when using poly bushings on both sides. Now I don't know if your aftermarket rods are stronger than the stock rods (probably are), but you might want to look into that before using poly on both sides. Second, You used a force gauge to check the preload on the steering rack? Seriously?

Well the biggest bummer right now is that if the problem spontaneously went away, you can be sure that it will spontaneously come back again. Are you double dog sure it doesn't have anything to do with the electrical work you just did? You were messing around up front near the parking lights with the fan install. I know it's unlikely, but just seems too coincidental.

Well duh. Who doesn't!!?

Well that's a bummer. So looking at that fuse and the cover, here's my forensic analysis of the whole situation... (Warning... Heresay and theory alert) You have (or had) a dead short somewhere in your parking light system. That dead short occurred spontaneously as you were driving. Hit a bump? Something maybe that had been very close to shorting for some time finally picked last night to be the time when it went the rest of the way? Or maybe it's related to the electrical work that you have been doing recently? That spontaneous dead short blew the fuse so violently that you ended up with arcing sparking inside the glass tube along with ionized air and metal mist from the vaporized fuse material. That ionized air and metal mist allowed an arc to form (just like welding) and that arc not only allows current to continue to flow, but it also produces mucho heat. Certainly enough heat to crack the glass and melt the fuse block plastic. So, you've got this dead short in your parking light system and a fuse that is still passing huge current even though the metal strip is long gone. You're pulling many amps through the dead short, and because of that, your headlights go dim (which looks to you from the driver's seat like they went out completely). Then after some period of time, the arc finally stopped. Maybe the fuse metal burned back so far that the arc could no longer be sustained. Maybe when you flipped the headlight switch back and forth a couple times, you were able to break the arc? Maybe whatever shorted in the first place became spontaneously unshorted? Maybe the high current melted and opened a wire somewhere? In any event, the high current draw stopped, your headlights were able to come back to better brightness, and everything else, other than the parking lights, went back to normal. And for those of you who are wondering "OK, so if this is all true, then why didn't a fusible link blow?" Well here's why... For whatever reason, in Datsun's infinite wisdom, there are a bunch of circuits that hang directly off the alternator with no fusible links between the alternator and said circuits. They are a direct connect to the alternator, and in the case of a hard fault, are happy to suck down as much current as the alternator is willing to produce. I don't know if this is a design oversight, or on purpose for some reason, but that's the case, and yes... The parking light system is one of these "non-link protected" circuits. So, my first question is... Is the short still present, or did it fix itself as mysteriously as it occurred? You can't simply check with an Ohmmeter because all the bulb filiments will make it look like a short to ground (even though it might not be). I would put a new fuse in that spot (like a 5A fuse?) and turn the parking lights on while you watch that fuse at the same time. if the parking lights come on like normal, then you've unfortunately got a continued mystery. If that fuse goes up like a flash bulb, then you need to start disconnecting things until you find out why.

The 78 fusible link for the headlights does headlights only. Nothing else is on that circuit. What's the state of the issues now? Is everything back to normal, or are there still lights that aren't working?

Dennis, That would be such a fine site to see. Thanks for the tip. I'll be sure to do that if I ever make that journey!

So do either of the two restored service stations pump gas or work on cars, or are they both just tourist stops now?

Ignore the dents in the dash and focus on the rest of the car. Pretend the previous owner did it.

That's cool. If I had more time and more money, I'd do all sorts of expensive time consuming stuff, and one of them would be to drive the whole Route 66 from one end to the other.

I'll let you know in a week or so. A local Z buddy of mine recently ordered a bunch of those thinking they might look good. They'll be here shortly and when they get here, we'll try them out to see what they look like. As for a name? No idea. That technology is moving so fast and furious right now that I don't think there are standards to describe them. Other than the BA9S base, I don't think there's anything to describe them other than "oversize" or not.

Yup. That's exactly what would happen. The incandescents will always dim just fine, but the fewer of them you have remaining in the system, the less you'll get the LEDs to dim. And by the way.... As far as the dimming function goes, the stuff like the brake indicator, turn signal indicators, high beam indicators... None of those are connected to the dimmer so they don't matter one way or the other. Leaving them as incandescents won't help your LEDs dim. Only the incandescents that are dimmed will matter. On the 78, the only things that are dimmed (besides the gauges themselves) are the hazard switch, the HVAC faceplate, the original radio bezel, and the A/T shifter bezel (if you've got an automatic). So if you've got a manual trans 78 with an aftermarket radio and have already updated the HVAC bezel, then you've only got one tiny dimmed incandescent lamp remaining in your system and that's the one in your hazard switch.

I don't get over to Hybrid much, but I did see the thread a while ago. I gotta say that I'm more than a little impressed. That's some nice work on such a huge undertaking.

Haha! Glad to help. So my previous owner removed my cargo straps completely and I've been looking for options. I did pick up a pair of old straps off a junker a while ago, but they are very faded. Supposed to be black, but they're a pale blue/gray. I like the ratcheting ability of your mod too. Nice work.

Wow. Very nice. So you're "Captain Overkill"? So you've got access to all sorts of machinery to cut that prototype head, and the only thing you can find to finish off your brackets was freehand on a belt sander?

Cool. So far. so good. I suspect that as you increase the number of LEDs in the system (and reduce the number of incandescents) your "range of dimming" will decrease. You'll always still be able to get full bright, but the "dimmest" lower end will move up. And with that in mind, I think I would concentrate on LEDs that are dimmer rather than brighter. Everyone selling LEDs seems to advertise how BRIGHT they are and all the customers seem to think that the brighter, the better. I've done a little bench testing with a few LED bulbs in spare gauges and I've come to the conclusion that you don't need much. Now, I also know that how much brightness you want from the dash is different for everyone, but I'm not looking for way brighter than stock. I want white, not necessarily a whole lot brighter. YMMV.

The problem is the huge disparity of currents between LED's and incandescents. If you make the pot large enough that the LED's will get completely dim, then your incandescents will all go completely dark in the first ten percent of rotation travel of the pot. And if you make the pot small enough that you get reasonably good control over your incandescents, your LED's won't ever get completely dark. I think the best solution is to use all one technology or the other and not try to mix the two. And if you DO have to mix the two, a PWM dimmer would do a much better job of handling the two differing technologies because it's a duty cycle based control instead of a resistance based current limit. I think that if you do switch everything over to LED's, a 400 Ohm pot would be a good place to start. You could use traditional fixed value resistors first though just to test the brightness and then once you're confident on the upper end, buy the pot. But be warned... I expect you're going to run into the same problem with the pot shaft being too short and will need some sort of extend like what I did for the PWM module I made.

It's the one that points toward the radiator. Vacuum from that front port should "T" to go to two places. 1) the distributor vacuum, and 2) the carbon canister control line. I think I've got a spare throttle body in the shop. I'll snap a pic or two and label the connections when I get a chance.

And while we're on the subject... I'm no bulb expert, but I did do a little digging recently as a result of some of the stuff I'm doing to my car and here's a little bit of "Bulb Theory 101" that I picked up along the way: The "BA9S" simply describes the BASE size and shape. It does nothing to describe the glass shape. For example: "BA9S" - Means "Bayonet base which is 9mm in diameter and has a single filament." Bulbs with a BA9S base can come in one of many different envelope shapes: G = "Globe" - These are spherical (like a globe) T = "Tubular" - These are usually longer than they are wide. S = "Straight" - These are supposed to have straight sides, although they often do not...? In catalogs, the envelope shape letter is followed by a number, and that number is diameter if the glass envelope measured in eighths of an inch. Yeah, I know... I didn't make up the nomenclature. So, for example, you'll see bulbs listed as "G3-1/2" or "T3-1/4". What that means is: "G3-1/2" - Means "Globe (spherical) bulb with a globe diameter of 3.5 eighths in diameter or about .4375 in diameter" "T3-1/4" - Means "Tubular shaped bulb with a globe diameter of 3.25 eighths in diameter or about .406 diameter" I did a bunch of digging into the original bulbs (Toshiba A12V3.4) and I've come to the conclusion that they are not available on the free market. They are a BA9S base, but the glass portion measures about .310 (8mm) diameter. Using the modern nomenclature, this would be a "G2-1/2" and I've not found that size anywhere. Might be completely ubiquitous on the other side of the planet, but not here. I've not checked if the larger G3-1/2 bulbs will fit through the hole in the back of the gauges, but I have confirmed that the small T3-1/4 bulbs fit fine. In other words: "A bulb with a BA9S base and a T3-1/4 envelope fits in the dash gauges." Sorry you started the discussion?