FastWoman

A valve train with accumulated varnish can have sticking problems. Try running a high detergent motor oil -- or possibly adding a quart of Rislone. I've also flushed engines with Gunk with great success (including on a previously owned '75 280Z and a 2001 Z3), but I was strongly cautioned against that practice by others on this list. It seems that if you flush an absolutely filthy engine (like my '78), your engine can suffer a loose-sludge attack. (I'm doing fine so far, but I'll be changing my filter at 500mi.) Anyway, that's the solution for sticking valves -- getting them clean.

Well, it's not at all a subtle problem. It's obviously a major malfunction in your fuel delivery. Look into the mouth of the air flow meter. Does the flap close, or is it stuck wide open? Do the injectors go "tick tick tick," or are they held wide open? Perhaps the fuel injection computer is malfunctioning? Is your fuel pressure extraordinarily high? Good luck with it! Sarah

De nada, TomoHawk.

Sticking/sluggish valves could definitely cause a cylinder not to fire. Maybe that's the problem. There could of course be other causes, like the injector not firing. I clean a lot of things with Chemtool B-12. I don't know whether there's a spray version of this product. Some form of spray cleaner (a strong solvent) would be good for getting the product into tight areas (e.g. inside the valve springs). Find a product that attacks varnish, which is your culprit. You don't need to clean away the oil; the solvent will do that for you. You will need to mop up the solvent periodically to keep it from draining back into the oil pan (i.e. down the timing chain tunnel). If you park the car facing slightly up-hill, the oil and solvent will collect in the back of the valve area (away from the chain tunnel). You might start the process by removing all of your spark plugs, so that you can turn the engine easily by hand. Spray down your valves, turn the engine, spray again, turn the engine, spray, etc. After you've seen that none of them are sticking with hand turning, then work them a bit faster with the starter. Don't turn the ignition on. Open your carb to full throttle, with the choke off. Disconnect the wire from your ignition coil to your distributor (just in case). Clip a wire to the solenoid of your starter. When you touch the other end of the wire to the + of your battery, the motor will turn. Do this very carefully (!!!!). I don't know if the motor will turn fast enough to sling any oil out of the valve area, but be aware of mess potential. Spray the valves again, turn the motor (with the starter), repeat, repeat. Watch for wobbling rockers. Listen for any snapping sounds. If you see/hear/experience any of these things, STOP IMMEDIATELY, and return to working the valves by hand. When you are convinced your valves are working freely under starter power, put it all back together, and start it up. If it runs OK, then shut it down. Finally, put a quart of Rislone in your oil. I haven't used this product YET, but it comes highly recommended to me. It's extremely high in detergent and will work on your sticking valves. You might have to drain out a quart of regular oil to add the Rislone. You can also put a bit of B-12 in the gas tank. I've successfully cleaned injectors and intake valves this way, but it takes a bit of time and repeat treatments. Pack up some tools in the hatch (in case you need them), close the hood, and go for a very long pleasure drive. Don't get too far from home. Stay within towing range. Don't worry if the engine isn't running absolutely perfectly, as long as your valve train isn't falling apart and you're not hurting it in any way. Hopefully that will free up your valves for you. One last note: I've never done this on a car with valves sticking as badly as yours. Others may be able to advise you from a standpoint of more experience. You should consider my advice only as a starting point but should probably research a bit further before actually trying anything. Good luck! Sarah

The 280Z tach circuits are apparently proprietary and mysterious. I've opened up a '78 tach, and there are some key black-box components. I suspect nobody has a schematic, except for Nissan. The trigger from a stock 280Z is not a clean 12VDC pulse, as it has some high voltage transients from the coil kickback. I don't know what voltages are necessary for the tach circuit to trigger. It might even trigger off of a 5VDC TTL pulse. If you need to convert 5VDC to 12VDC, just make a little comparator circuit. A 741 chip should do. Wire a potentiometer (maybe 10k) between +12 and GND, and wire the center tap to the - input on the 741. That pot is used to adjust your trigger voltage, and it should operate just fine over a very broad adjustment range. Then wire the 5VDC TTL pulse from the MSD to the + input of the 741, probably with a 10k resistor in series. Then wire the output of the 741 to the tach's signal post. Simple circuit -- nice beginner project.

As promised, here is an image of my original, under-hood stickers -- one for the emissions and one for the A/C. As I said before, cats weren't installed on '78 280Z's, except in California. As you can see, mine is a non-california ("non-catalyst") and low altitude version. Mine has a generic cat on it for some reason. I don't think there are any Virginia laws relating to retrofitting of cats. (My '66 Mustang doesn't have to have one.) As has been suggested, any cat should be fine if you have to put one on. Just be careful that it has adequate heat shielding. BTW, I moved from Ohio a few years ago, and they weren't doing emissions testing or even state inspections when I left. Are they testing emissions now? Perhaps that's a Cleveland thing? Peace, Sarah

Is your fuel fresh? You'd be surprised how fast it can turn to a gummy syrup when just sitting. Then it will gum/glue your valves in place, causing exactly the problems you describe. I've had that happen with a 280Z I let sit up for about a year. This happens especially if you run the engine on the old gas (and it will seem to run "OK") and then let it cool off (which lets the hot gum solidify). In any event, I checked a previous post of yours, and you talked about a stuck valve. Be VERY CAREFUL when your valves are stuck, because they can collide with the pistons, and your valve train can fall apart (as happened to you). I'd recommend pulling the valve cover and the intake manifold and cleaning/freeing the valves from both sides with a strong solvent, working them manually. Run the engine again only after you've resolved the sticking valves.

It doesn't sound like a bad bearing to me, as it only has one constant pitch that doesn't vary with engine speed. I'm speculating that it has no relation at all to lubrication. It sounds like some sort of air valve to me -- one of the emissions valves, perhaps -- or maybe a vacuum control. Anything making that loud a noise should probably vibrate pretty well. I'd start feeling around for vibrations in the different parts that have diaphragms.

I presume your '78 is a non-California model. Right? If so, there's no cat on it. Having said that, mine is also a '78 non-California, and someone actually did put a cat on it. Aside from the cat, I don't think there are any other exhaust issues. (Are there?) Anyway, I'll take a pic of my sticker for you when I find a moment.

Sounds like my discovery that my serial # didn't indicate a 5-speed (i.e. HLS30F). At first I fretted that it wasn't original, but then I reminded myself how much I wanted to swap my 4-speed for a 5-speed on my prior Z. I like my 5-speed.

I'll bite. Put a vacuum gauge on it. The needle should be steady and the vacuum strong. It won't be strong if your engine is missing, of course. However, it should definitely be steady. If it's bouncing all over the place, you could have sticking or leaky valves, which would definitely cause the cylinders to miss. The advice I seem to be getting for a dirty engine is to use Rislone. That would have been better than flushing, which I did, and which liberated incredible amounts of sludge all at once. (Gradual is better.) Test the compression. Do all the cylinders look normal? Pull the plugs, and read them for clues as to fuel/air ratio problems, oil, etc. FAIW, I had major headaches with an old 1975's fuel injection system. Even if your injectors fire, are they injecting the right amount of fuel? How does your exhaust smell? Rich? Lean? (Again, what do the spark plugs tell you?) I ultimately found my AFM had been damaged from backfire, and the engine ran much better after I bent the metering flap back into shape and recalibrated. There are lots of things that can cause these engines to act up. It just takes a slow, methodical approach to work through all the bugs. Then they run great!

Thanks for all the great advice, guys! OK, then. Drawing upon all of the advice above, I'll go ahead and drive the car, cautiously, for a few hundred miles, swap the filter, top off with Rislone, drive another thousand, and then change the oil. I'll make a switch to the Chevron Delo w/ STP (for zinc) at that point, with a fresh Bosch filter. If anything becomes "different" on my gauges -- either oil pressure or temp, I'll go ahead and change oil right then. Of course I'll let the appearance of the oil (black) also tell me when I need to change. Wish me luck!

Thanks for your advice, Gary and Will! Given that I've done what I've done, where do I go from here? I've got Castrol 10W40 Syntec in it and a fresh Bosch filter. Gary, are you suggesting a complete oil change at 500 mi or simply a filter change? The order of oil flow seems to be from the sump to the pump to the filter to the oil passages, and the pressure sender is on the output side of the filter. I would presume if my filter became clogged, the pump would blow out the filter material, and then I'd still have oil pressure, but with contaminated oil. I probably wouldn't notice anything on my oil pressure gauge. Correct? I'm guessing the conservative approach would be to immediately drain the oil, pull the oil pan, clean it, and then put in fresh oil and a fresh filter. Should I do this? Thanks again for your help!

The R134a operates at much higher head pressures and often doesn't get along well with existing hoses, coils, and configurations. I've had two cars retrofitted to use existing coils and hoses. The budget retrofit (Fred's no-name in an old Cadillac) blew up. The expensive manufacturer retrofit (Saturn) works fine but leaks. I've also put a complete Vintage Air 134a system in a Mustang, and of course it works great. However, that didn't involve a combination of old R12 parts and new R134a parts. I'd stick with R12 as long as feasible, as long as it works.

Hi all, I could use a bit more advice, regarding the 160K mi original engine in the '78 I recently bought: I flushed my engine today (Gunk) and changed the oil. Then I opened up the valve cover to adjust the valve lash. I was rather surprised at what I found. Although the moving parts were more or less clean, the valve cover and top of the cylinder head looked like the inside of my smoker after a 16 hr round of smoking. There was a varnishy/gummy crust that averaged maybe 1mm thick, with much thicker build-ups in some areas. The Gunk took down some of it from the valve cover walls in sheets, in line with oil spray from the valve train. I scrubbed the remainder of it from the valve cover with B-12 and a toothbrush, and I scooped out the piles of compacted sludge from the large cap-head bolts with a screwdriver. I then wiped down the valve train as best I could to remove additional deposits. As I looked down the timing chain tunnel, I could see incredible amounts of sludge everywhere -- perhaps as much as 2-3mm thick. I'm sure there are similarly impressive deposits in the crank case. I'm presuming this engine has never been flushed or cleaned, and I've frankly never seen the inside of a 160K engine that hasn't been flushed. I've always bought younger engines and have periodically flushed them. Would this degree of sludge accumulation be expected/ordinary? So I'm wondering how I should approach cleaning out the rest of the stuff. I'm thinking of using a quart of Rislone, to work away at it with detergent. Perhaps I'll change oil again in 1K miles, or when the oil gets black, whichever comes first. Then I'll change oil/filter after another Gunk flush, using old-fashioned, non-synthetic oil (I used blend this time) with Rislone. Then I'll repeat and repeat until everything is clean. Will this work? Is this too aggressive? Do I have to worry about loose sludge in the oil pan at this time? Do I need to pull the oil pan? I've never been down this road and would appreciate any advice -- and any modifications to my plan of action. Thanks! Sarah

Update: I still haven't tested the cold start, but I flushed the engine and found it to be pretty gunky. Sticky valves? I then pulled the valve cover to adjust the valve lash. I found that the #6 exhaust was a bit tight and MAYBE could have prevented the valve from closing completely on some cycles, allowing exhaust gasses to backflow into the cylinder during the intake cycle. Just speculation, but that could have caused the backfire. Fingers crossed... I haven't experienced backfire since then, but then again I haven't started the engine cold more than a single time. The exhaust still puffs a bit. I only put a dent in the engine's gum and varnish, so sticky valves are still a possibility. I think continued de-varnishing and de-gumming is the most likely solution.

Mmmmm... It turns out that it doesn't make any difference whether the vacuum advance is disconnected. It times the same at idle. I'm wondering whether I have a good vacuum at the advance. I didn't have time to test today, as there was a beautiful sunset we wanted to take in on the water. The vacuum line to the distributor has a T connection also going to the carbon canister. That might be compromising the vacuum. Question: Is the carbon canister really necessary? Does it do anything for engine performance? Would it still even work after 30 years? I'll look into these and other matters tomorrow.

The service manual says 800 for manual and 700 (in gear) for automatic. I used the right RPM -- just had the vacuum advance connected. ;-)

Thanks! I'll give it another go this evening with the vacuum advance disconnected! Regarding the transmission in gear... It's a 5 speed manual. I think I'll keep it in neutral!

Hi, Gee, it's been a while since I've actually had to time an engine -- long enough for me to forget a thing or two. I just replaced my distributor, and therefore I need to do this. Here's what I did: Warmed up engine. Set idle to 800 RPM. Connected timing light. Set to 10 deg BTDC. Readjusted idle. Rechecked timing. Tightened set screw at base of distributor. Finished. As I was doing this, I noticed that there was quite an RPM drop between, say, 20 and 10 deg BTDC. The engine seemed to run smoothly, but that seemed quite an excessive drop -- perhaps a few hundred RPM. Moreover, my engine vacuum is a few pounds below where it should probably be. Stupid question :stupid:: Am I supposed to disconnect the vacuum advance before setting the timing? The Datsun service manual didn't tell me to do this, so I didn't. Somewhat smarter question: At about how many deg BTDC should I expect idle speed to peak? Another question: Does an excessive falloff in RPM between the "happiest" setting and the mfgr's specified setting suggest any particular engine problem? Finally: Are there ever any reasons to set timing more advanced than the 10 deg Datsun specifies? Thanks for any advice! Peace, Sarah

I haven't tested the cold start yet, to be honest. I do need to replace the fuel line to the CS injector, so perhaps I can test it at that time -- by jumpering it to the battery and seeing if it passes air.

Hi Unkle, Thanks for responding! The air filter wasn't breached, so I know nothing got into the intake. Distributor is clean, just corroded/stuck at 10 deg BTDC (another thread about vacuum advance -- distributor to be replaced today). I've been through the vacuum lines and wiring pretty thoroughly. I've not found anything chewed. No evidence of rats -- only a small mouse nest. Overall the engine runs quite well (better, now that I've fixed some vacuum leaks). Startup is just a bit rough after the car has sat a few days, and I occasionally have a miss, resulting in an exhaust "puff."

Dunno... I have two general problems, possibly interrelated, that might be attributable to multiple causes. I was simply asking which are the more likely of these causes, as it seems better to throw money at the cheaper and/or more likely causes first. Do I have too many questions in one thread? Should I have posted in multiple threads? It seems unlikely that the dozens of Z owners who have read this thread would not have a clue about any of the questions I've asked. I'd be very grateful for any thoughts about any of these questions. (Responders need not answer *everything* to provide info that would be helpful/useful to me.) Again, I greatly appreciate any help anyone is willing to offer me.

FAIW, it's really hard on all the circuitry (e.g. fuel injection computer) to disconnect the battery while the engine is running! While you're diagnosing, and when you need to kill the motor when it fails to shut off, you're much better off pulling your ignition coil wire. (Wear Playtex gloves, so that you don't get zapped.)

Alex, I think you mentioned that you put antifreeze in the radiator just prior to this happening. FAIW, antifreeze has anti-corrosion additives, so I'm guessing you won't encounter pronounced rusting/corrosion anywhere in the engine because of its exposure to the coolant. However, I'd try to get as much of the coolant out of the engine as possible. I'd drain out all the milky oil and spray everything possible with WD-40, draining that into the pan too. After you remove the head (if you're doing the work), you should take it to a good machine shop and have them look it over for the potential problems others have mentioned (particularly warping). Get a price quote on any rebuilding work they recommend. Also inspect your cylinders. You'll probably see some coolant in one or two of them. Those are the ones you want to pay particular attention to. Are there any rust perforations in the cylinder walls? Turn the motor, so that you can see all parts of the cylinder walls. After you know what you're dealing with, THEN decide how to proceed. I think that's all Steve was suggesting. It was actually good advice. Good luck!