Zed Head

1978 280Z's don't use the ballast. The 15 volts is concerning since the 1978 cars have an internally regulated alternator. Should only go up to about 14.3 or so at most. High voltage can mess up your other electronic parts. The tach jumping is a sign of a failing ignition module or a failing tach. Sending out extra sparks, that the tach can see but don't affect the engine. Probably want to check the alternator first, getting the voltage right might make the other stuff right. Like Patcon says use a voltmeter at the battery, don't trust the dash gauge.

I think that other types of problems might be getting blended together in the comments. With the clutch pedal pushed in the engine is disconnected from the input shaft. So the clutch seems to be right, it disconnects the engine from the trans, like it should. With the transmission in neutral the input shaft is disconnected from the output shaft. since the car moves with the lever in the neutral position, apparently, then there's a problem with the transmission. Here's another possibility - neutral isn't really neutral. I assume that you are assuming that the transmission is in neutral because the lever is in the middle and/or not in one of the gear slots. Maybe the transmission controls aren't doing what they should. Are the shifter bushings tight? Can you get the lever in to any position that frees things up? Maybe the detent pins/balls aren't detenting. Here's another - a broken or loose shifting fork. It might not be releasing the coupling sleeve. If this was the case you might find that certain gear positions actually lock everything up since you'd be in two gears at once. Overall though it looks like you'll have to get in to the transmission to see.

If he's getting actual movement of the weight of the car he has some serious binding inside. Sounds like the shady mechanic. You can turn the input and output shafts by hand, easily, in neutral, with the transmission out and on the ground. There's no way it should move the car at all, unless there's a serious bind-up.

Just a guess but maybe it's a sign that the ZX module is gong bad. Shorting to ground lightly, causing constant current through the tach circuit. If you have a spare module a swap might show something. Or the higher current flow from the ZX module and the coil is damaging the tach.

The LSD isn't doing much unless you're turning. No clutches slipping. Might be a clue. Check the simple stuff like lug nuts. They'll make those kinds of noises as the wheel wobbles back and forth. Pretty sure also, that somebody just had a simlar noise and it was the half-shaft flange nuts/bolts at the wheel. Check all of your nuts.

The head gasket/block/head combinations discussion can get convoluted. Especially if you get in to what the high power guys do to their heads to balance the cooling, drilling holes and attaching extra coolant lines. Sometimes people assume that all of the passages available need to be open and flowing as much as possible but if you follow the Nissan design path it looks like they modified the head gasket to control flow, by blocking or reducing the size of certain passages. There was a picture recently that showed it clearly with rust spots on the head gasket where the ports were blocked. So if you're mixing head and block you have some thinking to do. I've always thought that the head gasket should match the head. The head is what warps if cooling is bad, the block is essentially just a reservoir of coolant. And it's not a block gasket, it's a head gasket.

Exactly. I was just adding to the lack of clarity. For amusement.

Correct.

That color is hot.

The fragments would get splattered up to the valve cover and around up top but once they get to the pan they have to go back through the filter before reaching a bearing. Might be interesting to split the filter open.

People usually catch it sooner but, yes, that's the typical pattern. The pressure is on the lobe. A picture of the base circle might show a nice untouched surface. Here's an old thread -

It looks like just wear. Once you break through the surface the lobe can wear quickly. The base circle looks intact, it's on the rocker pad in the picture, which indicates proper valve lash. Fairly common, especially during break-in of a new camshaft. Some of the members here have burned through some cam lobes. @madkaw I think, for one, if I remember right.

The sporadic nature of your problem suggests those two electronic parts. There's not much to the HEI module wiring, on a 280Z. You can connect it temporarily in the engine bay with some jumper wires and a screw or two.

I didn't read back through all of the posts but this one and the following kind of suggests either an ignition module going bad, too many sparks causes too much fuel, or an ECU going bad. Tthey tend to go rich first then just die. You mentioned what what the tachometer needle was doing when it was starting to die. You talk about "roaming" and that's a sign of an ignition module dying. Mine showed a jumpy needle, reading high, as it was kicking the bucket. A $25 GM HEI module is a simple quick test, and always good to have around anyway.

Thanks GN. It was a fun project. I realized afterward that a person could probably bend a single piece of steel to fit the bolt positions on the side of the tunnel, then drill holes for mounting and the the GM mount. No welding, just good bending and 5-6 holes drilled. That Technoversion mount is a pretty nice piece of work. Hard to do it yourself for the same value.

I bought a 280ZX engine and it had bolts instead of studs. They looked factory. Seems like the basic question hasn't been defined. What are you trying to accomplish by changing from the factory setup? If you don't care about the studs getting pulled out why not just use thread locker?

If you want to get more "forensic" you can consider what happens when the engine runs and/or the car is driven. Road debris will hit the inside of the fender wells, PCV vapors will coat the inside of the manifold, the distributor cap and rotor electrodes will darken and pit, carbon will deposit on the spark plug threads and insulator. There's a bunch of small stuff that should look like new after just 350 miles. You might even find a 43 year old piece of gravel in a tire tread, or, the clincher, a pop-top from a soda or beer can.

If you look closely at the yokes, and the contact points, and its shape you can see that the design is kind of self-correcting, or self-leveling. Easiest to see on used parts. There are two sharp contact points with the manifolds and the surface under the nut is round, You probably want to maintain the sharp contact points to avoid putting a bending load on the stud. Polish up the rounded surface and make sure that the stud doesn't contact the inside of the hole. It's a very loose fit, so it can move, I assume. A crude looking thing with some serious ingenuity in it.

It won't stress the u-joint but it might lead to vibration due to u-joint misalignment. The transmission output shaft and the diff input shaft are supposed to be parallel within a few degrees. Most people don't have problems with it though, apparently it's "close enough".

If you use self-locking nuts they'll probably pull the studs out on the next removal. Nissan did not even use lock washers. Actually, they didn't even use flat washers, where the yoke was used. Stud, yoke, nut was all of it. The mismatched flange thickness is the standard problem with headers. John Coffey suggested cutting flat washers in half and tacking the pieces on to the header flange as a fix. Requires a welder of course, but it was a simple and effective solution. http://www.carpartsmanual.com/datsuns30/Datsun-Z-Index/Engine-280Z/Manifold-Egr/From-Aug-76

Blowing the loose dirt off with light air pressure should be okay, or brushing.

Better check your ratios. Might want a diff also. Or keep the 71 4 speed for a while.

The old way of telling if an odometer had turned over was to see if the 0's were on the same line. Yours look pretty good. Seems like the more fundamental question might be "were all of the 280Z's delivered from Nissan perfect on arrival". That seems to be the assumption for people critiquing yours. Who knows.

Can anybody read this? Good data right there. Engine serial number, etc. Build date is on the door jamb tag. Lots of highly suspicious people out here. Nissan made mistakes on these cars, but it looks like it what the guy says it is, to me. Why are the intake manifold bolts orange? OMG, it's been molested...

It might help your thought process to realize that the head "gasket" is actually three gaskets in one. The metal cylinder sealing rings, the copper oil passage sealing rings, and the composite water passage sealing material, that also positions and holds the other two seals together. Consider each one separately.