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NC280z

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About NC280z

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    Advanced Member

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  • Location
    Havelock,NC
  • Cars
    1975 280z, 1987 300zx *sold*

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  1. NC280z

    Rebuild N42 Head

    Fortunately they sent a return label without any difficulties, I'm just waiting on it to arrive at the retailer for a full refund. Based on the box the head came in, it would seem that Go-Powertrain is a storefront for Allied Motor Parts from GA, and AMP does not have very good reviews. Oh well, on to the next project.
  2. Hi all, I was doing a bit of work on my '75 280z and noticed something odd on my passenger side strut tower. The seam closest to the front of the car for the passenger side strut tower has a few spot welds that are curled up, the rest of the strut tower spot welds/seam is nice and flat. I've owned the car for 7 years, and I don't recall the previous owner mentioning any sort of accident history. Is this indicative of damage from an accident, or just something resulting from age or factory oversight? Nothing around the area is wrinkled, or suggests any sort of major accident.
  3. NC280z

    Rebuild N42 Head

    The pits on the deck were my biggest concern, that and one of the valve guides is so corroded that it looks like the upper portion of the guide is missing. Overall, it looks like they shaved the head, painted it and shipped it out. I don't know how you get so many metal shavings in the box it was shipped in, it's as though they took it off the mill and just chucked it into a box and sent it out. Not too happy, I've sent a polite request to return the item, so we'll see how it goes. As always, I appreciate your input (and sanity check!) datzenmike. I'm glad I wasn't over-thinking this one.
  4. NC280z

    Rebuild N42 Head

    Good evening all, I recently purchased a rebuild N42 cylinder head from "Go-Powertrain" to prep for a larger cam and use on another build and noticed some things with this remanned unit. Cylinders number 5 and 6 have a bit of pitting, both in the chambers and on the deck of the head. I haven't measured the head yet, but I'm guessing it's been shaved a bit, as there's metal flakes all over the head, and some of the flakes are trapped under the valves along with bits of shop rags and other debris. Would these pits present much of an issue? I know that pitting is usually a sign of casting defects or of detonation damage, and that these pits can fill with carbon deposits and create hotspots that worsen preignition. I tend to be overthink things, and I don't know what to make of the pits on the cylinder head deck that are close to #5's combustion chamber. Run it or send it back?
  5. Good afternoon everyone, I'm restoring my '75 280z to the original radio system and need some help figuring out the polarity for the single (mono) speaker that these cars came with. The original speaker is missing, but the stock white and white/black wires are still there. The FSM and factory diagram available from XenonS30 and other sites do not show which color wire is which polarity, and the replacement Hitachi speakers I've acquired from a Datsun 1200 have the striped wire going to the negative side of the speaker. Does anyone here still have their original speaker setup, and if so, which wire goes to which terminal? Thanks in advance for any help you all can provide, I've searched just about every forum and have come up empty-handed. The majority of the posts on other forums only show how to determine a speaker's polarity, not the polarity of the wiring from the head unit.
  6. So it's been a few weeks and I'm happy to report that the oil leak has been resolved. I just figured I'd do a follow-up in case someone else runs into a similar issue, I'd recommend following the Chilton/Haynes manual's advice of coating the side-seals with RTV rather than with engine oil as recommended in the "How to rebuild" book.
  7. That helped, thanks! I ended up purchasing a 260z expansion tank, as it's made of metal (early 240z are plastic) and it had all the requisite vent inlets. It's very odd that the stock '75 setup didn't have all the correct inlets, I'm not certain what the stock setup would have done to ensure proper tank venting with all the extra outlets.
  8. Good evening everyone, I'm doing a refresh of the fuel system to my '75 280z (changed the topic of the original post to suit), and I've got a quick question regarding the vent lines on the expansion tank and the outlets on the fuel tank. It looks like the '75 model year was an oddball for differences between the fuel tank and expansion tank, as the fuel tank has 3 vent tubes but the expansion tank only has connections for 2 vents, plus the line that runs up front to the evap canister and a line to the fuel-filler neck. The main difference is that the '75 and older fuel tanks have a 1/2" vent tube right near the exhaust that was removed (probably for obvious reasons) in later model years and it does not have a mate of similar inlet diameter on the expansion tank. If I keep the topmost vent lines ran to the expansion tank, would it be alright to just cap off the 1/2" vent tube? What would you all recommend to cap the tube? The previous owner had a mishmash of adapters and tubes to run the 1/2" vent tube to the expansion tank, but left the 3/8" vent tube open to atmosphere which I believe has led to moisture in my fuel and a rapid degradation of the fuel itself. Tank photo borrowed from another Z site, as below:
  9. NC280z

    Cylinder Wall Damage

    I appreciate the quick responses! I tend to drift towards the worst-case scenario when I notice things like this. I had a machine shop bore and hone the engine, and I reassembled/refreshed the engine with new internals about 7 years ago and never noticed the damage during the reassembly process. During today's inspection I also noticed deposits on all of the pistons (see below), but all of them have this same even coating of deposits, which I'm guessing is normal for an engine like this. My idle AFRs are between 12.5~13.5, so a bit rich. N42/N42 with flattops, so compression is around 9.69~1 and it's happiest when on the rich side.
  10. Hey all, I decided to sneak an inspection camera into my Z's engine during some routing tune-up procedures and found a nick in the cylinder wall of the #3 piston, near the top of the bore. Attached below is a photo of the damage. The car idles well and draws a steady 20" of vacuum once warmed up, though I've not yet done a compression test to see if this damage has affected the engine overall. I also searched the bore for any foreign objects and couldn't find anything, so I'm not certain what would have cause this damage. Is this something I should be concerned with and address quickly?
  11. *FINALLY* figured out what was causing my leak. The side-seals were not sealing correctly and were allowing oil to pool up in the seal's registers and then leak down through the oil pan gasket. This also explains why my leak would continue even with the engine off and the car on a level surface. The registers for the seals were basically acting like little reservoirs of oil that would continue to leak until the next startup, where they'd refill and then continue the cycle after shutting the car off. Both of the old seals were completely soaked with oil when I removed them, and not all of the oil had the UV dye in it so I'm guessing it was a very slow and gradual leak that compromised the side-seals. I've compared the old side-seals to the replacements and found that the old seals are significantly smaller, I expected some shrinkage with age and heat cycles, but they're as much as 1mm smaller in both width and height. Now my question is how to seal the side-seals. The "how to rebuild your l-series" book and the FSM call for a ~1 inch strip of RTV on the groove in the cap, but I'm doing this replacement with the engine in the car and I don't have a nozzle small enough to reach into the groove to fill it with RTV. Has anyone here replaced side-seals with the engine in the car, and if so, how did you seal them? The how-to book also recommends coating the seals in oil prior to tapping them in place which seems counterproductive, since oil would likely prevent the RTV in the groove from curing properly. I followed the how-to book's guidance when I changed the seals last time and I think that this is why they did not seal correctly. My Chilton's book recommends coating the seals in RTV and then tapping them in place, which I may end up doing instead.
  12. I'll look into "the right stuff" gasket maker, all the threads that I've read on other forums have indicated excellent results. Could I use the right stuff to seal the front cover and rear main joints at the points indicated in the FSM and use a gasket as well? I ended up putting my car on stands and used my UV light to check for leaks last night, and it looks like both joints for the rear main have a slight leak, possibly due to the RTV not sealing up well enough. One quick question on side-seals, the "how to rebuild" book recommends leaving around 1/16th of the side-seal sticking out above the block, however, both of my side-seals are slightly recessed into the block, could this be an issue? I have new side-seals on hand, but I'd have to replace them with the engine in the car, which I'm sure is a PITA. The seals in currently in the block and the new ones I have on hand are the type which have the nail built into the seal, so it should make removing/installing them a bit easier.
  13. So I've used DanielC's tips and was able to fix the large leak from the front of the pan. I used a hefty brass drift and a set of feeler gauges to flatten and check the bolt holes around the perimeter of the pan. Unfortunately, I've got an extremely small amount of droplets coming from one of the rear main joints, and it looks to be coming from the block side of the gasket. I applied a thin bead of RTV as the manual specifies and I'm using one of the cork/rubber gaskets that datzenmike recommended. My guess is that either the bolt hole needs more work, or my application of RTV was insufficient. Everything's torqued down in a star pattern to just under 6ft-lb. I ran some UV dye through the oil and it's not a rear main seal or side seal leak (thankfully!). It's not enough of a drip to worry about yet, I'll probably readdress this at a later time. I appreciate everyone's help in this matter, and if anyone has any recommendations for sealing the joints at the front and rear of the block, please let me know.
  14. Sorry to revive an old thread, I've flattened the pan using the methods described above and I'm going to reinstall the pan this week. I know to use RTV at the joints for the front cover and the rear main cap, but I'm debating on whether or not to use gasket tack on the pan side of the gasket. The gasket I ordered from MSA is the cork/rubber type, does anyone have any recommendations regarding gasket tack and cork gaskets? It's this brand of tack: https://www.permatex.com/products/gasketing/gasket-sealants/permatex-high-tack-gasket-sealant/
  15. Time Left: 13 days and 3 hours

    • WANTED
    • USED

    Looking for a coolant bypass line for a 280z, specifically the line that runs from the lower coolant intake housing to the underside of the thermostat housing.

    NO VALUE SPECIFIED

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