Chickenman

I believe that unit is the Voltage Limiter for the gauges. Water and Fuel gauges work on 9 volts. The rest of the car works on Battery voltage which is higher. This instrument Voltage limiter knocks the alternator regulated output down to a staedy 9 volts. This produces more accuracy in the guages and also reduces heat buildup in the operating coils in the gauges. We used to replace them quite often in the dealerships. Some models ( not all ) had a separate part number for the instrumentation Voltage Limiter. Some you had to buy a complete Speedo or Tach to get the unit. I can't remember if 240Z had a separate one available or not. RatsunNet has an article on how to replace a defective Instrument Voltage Limiter with a generic part: http://community.ratsun.net/topic/54598-bad-gauge-cluster-voltage-regulator-easy-2-fix/

The most expensive car you will ever own is an inexpensive German car.....

A 225vr15 that would have a huge sidewall height. Around 28" O.D. Nice for Tractor tires but not on a Z. The XVS is also an ancient tire, Produced in early 70's. What are you using this on? A big Jag or something?

Air cleaner material and shape can make a surprising difference to the fuel curve. We tested various air cleaner tops on 580 HP Pontiac 463 motor. Engine was baselined with a Moroso 14" drop base air cleaner with domed metal lid and 3" tall open element air filter. We lost 6 RWHP switching from a 14" Moroso Domed metal lid to a K&N Extreme filter top. K&N filter top lost HP and Torque through out the upper range. Vaccuum secondaries also started opening 200 RPM later. Air entering through top of K&N lid was creating turbulence with air entering from sides of the open element filter. K&N extreme filter top: Moroso Filter Top: Removing air filter all together picked up an additional 5 RWHP from Baseline results. A taller air filter, 4.5" or 5", would likely have negated that loss, but hood clearance forced the use of only a 3" tall filter.

The following site also indicates that both L28 N42 and N47 heads came with steel Intake seats: http://www.viczcar.com/forum/topic/4286-overview-of-l6-engine-heads/ Edit. I think the confusion may be that the 260Z also used an N42 head. Different part number of head for 260Z and the Intake Valve Seat part number is 11098-U8710. Vs 11098-N4210 in the 280Z N42 head. Both the 260Z and 280Z head use the same Intake Valve ( 44mm ). Might be some crossover of 260Z N42 heads to early production models of 1975 280 Z's???? Illustration #2 ( 260Z Intake seat ): http://www.carpartsmanual.com/datsun/Z-1969-1978/engine-240z-260z/cylinder-head

According to the information at CarPartsManual.com all L28 engines take the same Intake and Exhaust seats, and these are steel. The actual illustration of the Valve Seats is in a weird location ( at front of head gasket ) so people often miss the listing if they only look at the picture. Illustration #5: Insert - Valve Intake = 11098-N4210 Illustration #6: Insert - Valve Exhaust = 11099-N6810 http://www.carpartsmanual.com/datsun/Z-1969-1978/engine-280z/cylinder-head

Used to love Metal Masters. Made by Repco I believe. Haven't seen them in Canada for a while. .Great semi- metallic pad that could be used for just on the street, Autocross, Hillclimbs and Track Days. Ran them on my 71 Z and 73 Camaro RS. Should be available still in UK. Bendix Titanium were good as well, but Bendix closed down Canadian distribution some time ago...

I picked up 6 brand new Standard Blue Streak FJ-3 injectors for $165 on E-Bay. That's hard to beat There are still some for sale. http://www.ebay.com/itm/75-76-77-78-79-80-81-82-83-Datsun-280Z-Fuel-Injectors-FJ707-FJ3-/162241229221?hash=item25c654b1a5:m:mqP-kgYey2FHyrChcpHSIlg Injector seals and injector holder kits are dirt cheap. Most of the EFI issues are due to old injectors and corroded terminals. You can get a complete terminal replacement kit with Bosch spring loaded terminals for very little money. One of our members ( FricFrac ) sells a very nice kit. My 1976 280Z has an F54 block with flat top pistons, N47 head, 280 duration cam, headers. 2,5" exhaust and TWM 60mm throttle body. All running on factory ECU ( at present ). New injectors, good wiring harness ( perfect actually ) , new Airtex Fuel pump, Z31 Auxiliary Air Regulator Car starts at first touch of key hot or cold. Cold idle speed of 1.500 and settles down to a rock stable idle with a nice lope at 1,000 rpm, mid range is perfect, Driveabilty like a stock Nissan and I get 25 mpg on the highway ( 5 speed with 3.90 gears ). Stock L28's normally fall flat on their faces after 5,500 RPM. With the cam and other mods this one pulls HARD past 7,000 RPM. Having everything in good condition and smart tuning is the key. I've got the car running so good right now, that I put a Haltech ECU project on hold for now. Was going to swap it in this summer, but ended up driving Z all summer ( My Audi broke and pissed me off. So I parked it ). Z ran so good all summer, that it had me second guessing Haltech swap. ( That plus health and money issues ). I did get the car up and running with the Haltech controlling the fueling ...with ECU temporarily sitting on fender. But I'm hesitant to swap over now, because the car runs so good on the factory ECU. It's not perfect. I'm sure I'm leaving some HP on the table. But this is a not a competition car. It's just a nice Sports Car that I can have some fun with. At 62 I find that I'm getting tired of working on cars. Plus my body has put an end to almost all DIY work...

BTW, the factory EFI system can work quite well with a mildly modified engine...with some limitations. Camshaft duration needs to be kept no larger than your typical 270 or 280 degrees advertised duration ( .230" to .236" at .050 lift ) A proper ignition timing curve WITH a tweaked manifold vacuum advance really helps smooth out the idle. The fuel pressure can be raised a bit to support a mild cam, headers, 2.5" exhaust etc and the AFM adjusted to compensate. ( Raise fuel pressure with adjustable FPR to eliminate lean spot after AFM tops out around 4,000 RPM and then adjust AFM spring tension to lean out mixture at cruise and low RPM's ). The DSM and Toyota boys have been tricking out Air Vane AFM's for decades using that method. The AFM does NOT fluctuate at idle as widely reported in various articles... as long as cam overlap is kept reasonable and idle at 1,000 rpm minimum You are restricted with mild modifications with the Factory ECU as you really can't change injector sizing.. but it will support up to 200 HP with the right tweaks. A stand alone ECU just eliminates ALL of the issues with the factory ECU and then the sky is the limit on HP.

I agree with Rossiz. I would keep the factory EFI...especially over a Holley conversion. I have built and Raced Holley carbs for many, many years, and I would never switch back to them over a factory EFI system. Conversion to twin Su's or Triple Webers/Mikuni's sure. But a Holley 4 bbl would be a step backwards IMHO. The Holley is not going to like being perched above a stinking hot exhaust manifold... the Holley float bowls are even more sensitive to fuel peculation than the factory SU's. A really good heat shield and phenolic base isolator are a necessity. The installation position of Holley's with that manifold is 90 degree's to their design position and this can cause float level issues under hard cornering. Mixture distribution to #1 and #6 carbs is less than ideal as well. This picture shows the improper " sideways" mounting and the lack of a heat shield. Bad design. Holley aftermarket needle and seat are infamous for sticking open, causing massive flooding with raw fuel dripping out of the carburator. Use of Genuine Holley Needle and seats along with a good fuel pressure regulator will help alleviate the sticking N&S problem. However, the modular float bowl design of Holley 4150/4160 carbs always tend to have some full drip from the float bowls. Right on to the hot exhaust manifolds or header Not good.

Hmmmm... maybe now's the time to think about installing a nice Ceramic coated header???

PO probably used a head gasket with some sort of sealant that melts when torqued down. Another suggestion to try. Put your breaker bar back in the Intake port and try it again. But this time have an assistant whack the front and sides of the head with a hard Plastic head hammer. The Plastic head should not harm the aluminium , but should shock the head enough to break it free. That usually works for me. Jeff's idea of the 2 X 4 sounds good as does the Plastic Wedge idea, but I've never had a head stuck on that bad. Breaker bar in a Port usually works for me....

A lot of Circle Track cars use Evans. Pretty sure F1 and Indy cars are using it as well, or something like it. I've read some articles on it in Circle Track and Race Car Engineering magazine, and it's pretty impressive stuff. You do have to follow their flushing procedure very carefully though. IMHO, overkill for street use... but for extreme use and conditions it's the best coolant out there.

Curious as to why are you only using water in your Rad. Unless it's a track requirement... as for most Drag Strips? A proper coolant has anti corrosion additives s that are extremely beneficial when running aluminium and Iron together. I'm sure you know that. The Water Wetter reduces the molecular tension of Coolant ( Antifreeze in Canada ) mixes. This allows more wetting of interior surfaces than just Coolant without Water wetter. Coolant mix also raises boiling temperature, which is good for reducing nucleate boiling, which in turn reduces the formation of steam pockets. While the heat absorption capability of Coolant mix is slightly less than that of distilled water, the addition of Water Wetter does bring the W/Wetter plus Coolant mix much closer to the heat absorption capability of distilled Water. Personally, I prefer the additional anti corrosive capabilities and increased boiling point of a Coolant mix with Water Wetter. The anti corrosion additives of Coolant mixes are a big bonus to me. BTW, VW/Audi ( and Porsche, BMW, Mercedes) use a low sulfate coolant referred to as G12. The stuff is not cheap, but independent tests show it is vastly superior in preventing galvanic corrosion compared to Regular Green fluid or even DexCool ( yuck ). Pentosin makes an excellent product, much cheaper than you can get at VW/Audi dealers. As with any Coolant change, you should flush the whole system, although G12 can be mixed with other fluids, it decreases it's performance. But at least it will not turn into Red sludge like mixing Dexcool and regular " Green " Glycol antifreeze/coolant. I'll see if I can find the link to the test data. It's quite interesting...

I wouldn't switch to a flex fan. Personally, I've never seen one that works as good as a stock fan on any car. Flex fans flatten out at high rpm. That's their design. While this initially seems like a good idea, as it reduces HP loss... it also turns the Flex fan into a very good airflow blocker to the radiator. Effectively a 17" Pizza Pan placed right behind the rad. Plus they will slice your fingers or hand off in a split second if you make a mistake.. Plastic fans will badly bruise or even break a finger or wrist. But at least it won't chop them off like a guillotine!!! What does work on the track is careful consideration given to radiator ducting. You want air pressure high in front of the rad and as low as possible behind the rad. Box in the front of the radiator to the grille so that the high pressure air is forced to go through the radiator. The stock design has too much area in the nose for the air pressure to bleed off. A shroud on the fan is a must. Make sure you are running the belly pan. That lowers coolant temp significantly. Air stacks up in the engine bay at high speed and needs some way to get out. Consider adding hood vents or simply prop the hood open about 1" at the back . You MUST use hood pins if you do this. Don't rely on the safety latch!!! The hood opening idea is quite effective. We used to run our D Production Z's this way back in the late 70's early 80's. With good air management ( ducting and venting ) and a decent Rad, overheating should not be an issue in a Z under 90 - 95 F ambient. Above 90 - 95F ambient gets tuff on any car. We ran a 160 degree thermostat and no fan at all on the race cars. If you need a fan for street use and track use, the 7 blade 280Z fan with factory shroud and clutch is very hard to beat. Even some of the best electric fans have a hard time keeping up with the flow that a decent mechanical fan makes. Mechanical fans can use a much higher pitched fan blade and a wider blade than electrical fans. It's all pure HP required to drive the fan.And it's all a compromise. Stop and go traffic in Downtown LA with the AC on is much harder on the cooling systems cooling ability. than running 100 MPH on the race track

If you still need more oil pan clearance, you could always go Dry Sump. Yes I'm an evil person....

All good info. Owner needs to do some proper tests though. Backfiring under load can also be due to a weak spark. Something Siteunseen mentioned in an earlier post about checking the points and condenser.. A weak spark will allow a car to idle fine, but as soon as any real load is put on it car will lose power and can backfire. Will also affect plug coloring. Not to say he doesn't have a fueling issue or Vacuum leak issue, but don't over look the Ignition system either. A weak condenser can be an SOB to find. Solution. Brand new points and condenser if old ones are at all suspect. Don't know if OP has checked spark quality, but he should . Get a cheap plug tester ( less than $10 ) and open gap to about .060". With engine running you should get a strong blue spark and hear a bit of a " Snap". If spark is weak, intermittent or yellowish then you have an issue. Same with fuel. By an inexpensive fuel pressure gauge and actually measure the fuel pressure. Better yet, buy a good combination Vacuum and Fuel pressure gauge. Quality tools and equipment are always a good investment and will last you a lifetime. Assuming that things are OK "because there is lots of fuel in fuel filter " is not the way to test. Same with alternator. Put a volt meter on it and measure what it's putting out. Consider switching to an IR alternator down the road. Original Nissan regulators were pretty good in their day. But that technology is 40 years old now and the VR's available now are mainly Made in China crappola. OP needs to take a methodical method of diagnosis and eliminate causes one at a time with the proper instruments. Otherwise you chase your tail in circles. Wouldn't be surprising if he finds several small issue.

Very nice explanation Blue. Whoever did that re-grind in the last set of pictures looks like they did a beautiful job. Who was the Vendor?

Ha ha. My Brake check relay just died 2 days ago. 76 280Z. Wasn't sure where the sucker was located. Thanks to Google and Classic-Z!!

When I had my Autocross/Hillclimb Camaro, I used a K&N filter.... once. Didn't like it. Mechanical oil pressure gauge showed an immediate hot oil pressure drop of 5 psi. Indicating that filter medium was too restrictive. Went back to AC/Delco Synthetic oil filters ( Very good filters by independent studies ) and oil pressure was back at proper hot pressure. Gauge was plumbed with a -4 AN braided line, not your typical 1/8" Nylon POS. So gauge was very fast reacting and accurate. Just my .02c. I like factory Nissan filters on my Nissans and AC Delco on my Chevy's. Mann on my Audi. Mann would probably be fine on the Nissan or Chevy as well. Good filters.

Over 200 Classic Japanese cars at Waterfront Marine Park North Vancouver, BC. Aug,28,2016 Photo's start on page 6. Some beautiful cars, trucks and Motorcycles: http://www.the510realm.com/viewtopic.php?f=12&t=28977&start=75#p255449

Thanks Jim. I'll be giving them a call to see how much to re-chrome my 280Z Tail Light Bezels. No shops in BC that will do Plastic re-chroming.

Sorry for Trying to help people out. I like to explain things and pick out pertinent data, not just point to links and let the person wade through data. . Sometimes people miss the points buried in links. Sometimes people don't read the links. BTW, the Z-creations page is exactly the one I referenced earlier and is quite specific to our 280Z cars. I have no idea how you consider that " Generic ". And just because " You " got poor results, doesn't mean that others have gotten the same result. But I'm done with you. I've tried to be civil, but you Troll just about everything that I post. You have excellent knowledge on Z cars in general and I applaud you for that. But you are not as educated as you think in regards to High performance Modifications in general. You have undoubtably served the Forum very well, and have provided a lot of usefull information. But you also seem to have developed a God complex, consider yourself the sole expert on everything on this Forum and Hybrid Z. You have treated myself and others with a condescending attitude and arrogance. As a moderator you should be better than that. From now on I will simply not feed the Troll and not respond to any of your comments. I may even decide to just leave the forums. I've got better things to do. Of course that is probably your game and I believe that I can be a value to these Forums. I've certainly never received this type of disrespectful treatment from any of the other Automotive and Electronics Forums that I frequent. Pathetic... I'm gone. Richard B.

Glad you got it working. Don't know why ZH conversion didn't work using the Z-Creation method. But I have a feeling the difference may be between California and Federal models and involves the Floor Temperature sensor. Federal models do not have Cats and no Floor Sensor. However, they do have a fuse ( 1 A ) for the Floor Temp sensor. I've noticed that when something in the Charging circuit fails, both the Brake light and the Charge light will come on ( no charge of course ) and the Floor Temperature fuse will blow. V/Reg was getting flaky and blew the Floor Temp fuse. Replaced fuse and car charge again and Charge lite and Brake light went out. I have a Federal model ( Car originally bought in Arizona ). Also had a rear bearing fail in a 60 Amp External Reg alternator. Shorted out the commutator and again the Floor Temperature fuse blew.

Edit: In reply to ZH. From Post #10. I don't know what else I can say. Everything works exactly as it should and exactly like it did before. Don't know why it didn't work for you.... What car is that wiring diagram from in Post #9. It's not from a 1976 280Z FSM.