bjhines

...hmmm...^^^^ I run my current 240Z at HPDE and TT events once a month...I run autocrosses about once amonth also. I use factory 4 screw Hitachi carbys with no mods... the car puts out 138HP at the wheels..It pulls great all the way to 6500 RPMs...for as long as needed..well over 120MPH...I have absolutely no issues with cut out in corners...Roebling, VIR, CMP, Rockingham...brakes are my biggest issue..not fuel delivery. I used to guess at mixture settings until some dyno runs with an AF meter showed me that the mixture varied GREATLY under different conditions...I installed dual AF meters with twin displays....this took ALL of the mystery out of tuning my car...It runs reliably,cleanly, and powerfully. I must say that a lot of the "advice" I had received over the years about alternate fuel pressure and float levels was a bunch of BS. If you have everything up to factory spec..and tuned properly you will not have cut out problems under any conditions...with Hitachi or the siamesed/triple carbys.... I just went through this with a fella who had the same high RPM cut out you describe...It turns out that the cut out was not related to RPM as much as it was engine load and duration...it just happened to show up around 5k RPM under most circumstances...The problem was fuel flow rate...the steel lines had rusted around the battery tray area...a small pinhole had allowed rust to penetrate inside the line and apparently plugged the hole behind it...rust built up inside the line and almost closed it off...When I performed a pressure test on the lines the rusty area blew out and the problem became evident...once the steel line was replaced the fuel flow was back to normal and factory settings performed wonderfully.... If you want to do yourself a favor...get some time on a dyno..with a working AF meter in the exhaust....It will tell you exactly what is happening under various loads and RPMs. A note about air cleaners....The factory air cleaner is fantastic...there is nothing but noise to be gained by removing it and going with "pop" cleaners...or open element filters....I tried several different common filters and found that none of them made more than a 2 HP difference from stock... The stock filter housing covers and contains the element...it is much less likely to catch fire and burn in that steel box than when it is exposed to the free flowing air in the engine compartment...besides...when the hood is buttoned up and heat builds up...the factory cleaner will draw cooler air in from the front of the car...the "pop" filters just suck hot air off the headers... Triple carbys obviously cannot use the stock air cleaner...but "TWM" makes an airbox to fit them that uses a single cone filter on the snorkel tube.... Apparently Prieth took my comment about professionals the wrong way....I will not vouch for the average mechanic...HS education with some community college does not count as an experienced mechanic... but the manuals assume you know what you are doing..they are not written to cover all the bases for a home tinkerer.... If you have not done it before...get help from someone who has...there are soo many finer points to doing any job correctly that a newbie cannot hope to get it all right the first time...unfortunately...the fuel system is not very forgiving..and it is very dangerous if you do it wrong.

ok...engine fires are caused by fuel....fuel needs to get OUTSIDE the carby to get enough air to burn. YOU HAVE A LEAK...or an overflowing carby.... Were the aircleaners soaked with fuel when you had the fire??? This is common and could be the result of sticky floats...overly high fuel pressure, bad inlet needle valves.... If you have "performance" carbys...a common "upgrade" was "Grose jets"...Grose jets HATE gunk and trash in the fuel...They are great...until they see dirt or varnish. A common newbie mistake is cutting new rubber lines and failing to clean the little bits of rubber off the cut ends...another common mistake is removing and reinstalling hoses on BARBED nipples...the sharp edges of the barbs lift little slivers of rubber off the inside of the fuel lines...when you push the hose back on....the slivers are scraped off and end up sticking the inlet jets open. Soo many people miss the little things and screw up their cars.... A good mechanic is not just able to follow assembly manuals...he is also an expert at proper handling and assembly of individual parts...there is a lot more to it than the manuals explain... As far as your car is concerned....A complete fuel system rebuild is MANDITORY!!!!!! You absolutely MUST determine what caused the malfunction. You must also treat the other carbys as if they were exposed or prone to the same problem. Even if you find that the original problem was unique to only one carby....YOU MUST REBUILD ALL OF THE CARBYS NOW that they have been exposed to heat of the fire....All engine parts get hot....but the fire could have heated things far above their failing point. If you brought the car to me to fix...THE FIRST THING I would do is check fuel pressure...It does not need to be more than 1.5 PSI at any time....to ensure flow through undersized fuel lines you may hear of people running as high as 4 PSI...but this is unnecessary with a well thought out fuel delivery system...raising the fuel pressure will not make MORE POWER....It just makes your car burn. In any case...Fire is one of the most painful ways to die....It will also completely destroy your car...do not dick around with this problem...take it to someone who knows how to work on performance carbys on older cars...A Ferrari dealership would be the PERFECT place to find folks who know how to properly work on the siamesed sidedraft types. On occasion.... an improperly set spark advance will cause a backfire into the intake manifold while attempting to start the engine....with the extra fuel pooling/wetting in the manifold at cold startup...a fire can occur.....A carby/manifold fire of this type is easy to extinguish by contiuing to crank over the engine..... It may startle you....but simply continue cranking until it starts....once the engine starts...blip the throttle to draw the flames into the engine...the fire will almost instantly go out... Of course...if your aircleaner is on fire...you better break out the extinguisher...you dont want ashes and bits of paper or foam going into the engine. A little list for you to check.... 1. fuel pressure 2. inlet screens on each carby....functional and in good condition as well. 3. proper handling and assembly of all hoses and fittings....from tank to carbys..This also involves flushing the system into a clear closed container and checking for bits of trash...even one little spec can cause you problems. 4. check condition of fuel filter...look for bits of trash or sludge that may require draining and cleaning the fuel tank. 5. test flow through feed and return lines....a plugged return line can cause overpressure. 6. dissassemble each carby and check condition and operation of float and needle valves...in case you dont know...this involves blowing through a tube attached to the inlet and moving the float until it closes the inlet valve...stopping the flow of your breath though the tube...check float height at the point it actually stops flow...not where it "feels" like it is closed...you must actually test this while blowing air through the inlet....Something like aftermarket "Grose jets" will render the dimensions in the manual useless unless you actually test the jets while blowing air through them. 7. check the condition of the engine mounts and tranny mounts...A bucking engine can literally shake the floats loose in the carbys...although this is more of a problem with off road/all terrain engines.

I have put a few exhaust on 240Zs. It is a good idea to replace your engine and tranny mounts BEFORE you add your new exhaust...things may not line up properly when you attempt to replace them later on. There are a variety of headers out there...some will require custom stud lengths..most will work with the stock studs...some will require a great deal of trimming washers to even the contact between the exhaust and intake manifolds. They are all prone to flex and breakage of the outermost studs. It is a good idea to add a flex joint right after the 2-1 collector...this will take strain off the studs..but it will require extra support aft of the flex joint. The factory placement of the resonator just after the collector was done to break up resonance in the long straight run to the rear. I think this is a good idea...It has been suggested that it may add some midrange power when compared to a similar exhaust without it. Whatever you decide to use..it should be a straight through design...and it should be at least 8" long and significantly wider than the rest of the exhaust tubing....similar results could be obtained by placing the resonator at the aft end of the long run( just in front of the differential)...though the forward placement will even out flow through the entire run. Muffler choices are more personal...A Dynomax is a very popular muffler for Z cars. It has a sound that is similar to the stock Z-car growl...You can keep one factor in mind when making choices...A straight through design will ALWAYS be louder than a baffled chamber design.... I have heard a Z with a NA L28 with 2 straight though mufflers...one in the resonator location and one in the normal rear location...with 2.5" tubing it was LOUD!!...2 does not make it much softer than just one. When deciding tubing sizes...2.5" is the most popular....3" may not maintain enough gas velocity at low RPMs to scavenge properly...It has been said that Z-cars with 3" tubing sacrifice some off the line pull...I have never compared 3" with smaller sizes on a street car...most 3" systems are on race cars that do not need the low end "street" response. last item on the list.....A "resonator" exhaust tip can be very effective at damping the sound as it leaves the system...this can slightly reduce the noise.... most systems end with a short section of straight tubing... that can set up a popping resonance that actually increases the noise... Make sure you beef up the factory hangar points when you replace your exhaust...most of them are held on by 2 small spot welds...they are prone to breakage.

I would not have gone down without a fight.... then I would recoup any fines and or additional jail time by sueing the **** out of Best BUY. I WILL NOT be wrongly arrested without a major fight. I will beat the **** out of the security guard/cop before I go anywhere under those circumstances. Citizens of this country should not allow themselves to be arrested for dumass shiat like this....It is worth the battle and the bruises. I have done it before and gotten away scott free.....the officer and I suffered from a few injuries...but I guarantee the officer has more respect for his fellow citizens now. Just dont get your *** shot when his backup arrives.

I have a few comments here....assuming this is an L-6 and not a V-8 Hybrid. 1. The fuel filter is supposed to be placed BEFORE the mechanical pump. This is a general rule to follow here. 2. There is supposed to be a return line or your fuel pressure may surge. Go get another fuel rail that is functional. 3. You have not mentioned any evidence of contamination in the fuel filters that keep failing... If your tank is full of rust and water...I would not be surprised that you have gone through a whole box of filters in a few minutes run time. Nissan was soo thoughtful to have placed a DRAIN PLUG on the bottom of the fuel tank. Drain it and have a poly liner installed. 4. Go get a Haynes manual....they tell all You sound like a likely candidate for a FLAMING DEATH... The carby fuel system is as simple as they come... You should not drive it until someone with experience can take a looksee.

Quick Electrical checklist....for 240Zs 1. Make sure the original fusable link is in place... on the starter +terminal. 2. Any added circuits should be connected to the battery +terminal with a fuse at the battery. 3. Ground the engine block to the chassis with a heavy guage grounding strap...no lightweight body ground crap...we want to see big meaty wire. 4. make sure the battery ground -terminal has a connection to the firewall near the battery. 5. check and/or clean the lighting ground terminals in the rear clip, the dash areas, and the front clip. These are common problem areas...you might get a few more watts of headlamp intensity. NOTE: Adding circuits that bypass the original harness (attached to battery +)..... will cause the AMP guage to read a high charging condition when using the new circuits.... Just use a volts guage instead.

I see the o2 bypass circuit... i can only assume that it is feeding voltage from a thermocouple sens wire back into the o2 sensor wire....as far as the heater element...that is obvious..although I would use a 50 watt resistor and keep it away from flammable materials. some people seem confused about the operation of these sensors... The actual sensor outputs voltage to the computer...anywhere from 0.01 volts up to about 1.0 volt....the only difference in wideband and narrowband sensors is the range of measurable air/fuel ratios. the wideband picks up a wider range without spikey voltage swings..... as far as the sensor just operating on and off modes in a repeating pattern every second...that is your cars computer in closed loop sensor mode doing that.....the sensor will simply track the actual a/f ratio...the computer is alternately forcing the engine to run rich then lean over and over again....all this happens at idle or part throttle....look up closed loop mode in google.

Ohh....My manual for my 1972 240Z says to use 93 or 95 octane fuel. I imagine the 1970-71 models would require 95 octane...as they had the highest compression of any Z car ever. High octane fuels have been around since WW2... Consumer grade gas was lower octane in the 40s and 50s because the average Joe's car had a very unsophisticated motor. Folks who drove high performance cars went to the airport for gas. High octane consumer gas became more expensive and harder to find after lead was banned... You can purchase gas at your local airport and pump it directly into your car IF.... you have no restrictor plate in your filler tube.... The rule is...you can only pump avgas into a vehicle that can use the large sized filler tube. No gas cans...no funnels allowed... If your local airport operator says no...just mention that you can actually fit their large sized filler into your antique car...with no funnels or other aids. Be careful when you pump from avgas pumps....they flow about 5 times the rate of a consumer filling station...

There is a neat program about the history of gasoline....on History channel...I think.... Moridin has the closest correct answer.... Heptane = 0 octane rating Octane = 100 rating. This is only the basis for our "octane rating". It has nothing whatsoever to do with the actual compounds in the fuels we call gasoline. gasoline contains many diffent carbon chains.... In fact current day gasoline may contain varying quantities of compounds anywhere from 6 to 10 carbon chains long. These compounds have been "cracked" from longer molecules during the refining process using heat and catalysts.... In fact there may have been several cycles of cracking and recombining of these molecules to get the mix we call gasoline. The cracking process was developed to get more "gasoline" grade fuel out of each barrel of oil. It has been modified to get not only more gas...but better gas for high performance engines. The actual "octane" rating for these compounds has been further modified by a process that "joins" the loose end of the carbon chains in a RING shaped molecule that turns out to have enormously higher octain ratings than the linear chains.....although it is the same chemical. Additives like Tetra-Ethyl-Lead further improved octane ratings as the need for detonation resistant fuels increased with high performance aviation engines in WW2. Countless other compounds have been developed since then to replace lead with less hazardous substances. Other additives help stabilize fuel, clean the engine, and reduce emissions. Most importantly.... ALL FUEL OF A GIVEN RATING IS THE SAME....NO MATTER WHERE YOU BUY IT IN THE USA. All the distribution companies use the same infrastructure to pipe the same fuel as everyone else. Ahhh....but you say that Amoco fuel "smells" better....or soandso fuel burns better...Yea Yea Yea...There is a difference at the pump....but the only real difference is in the ADDITIVES that the individual fuel companies put in their alotment of gasoline...that is done locally at the depot where the gas company fills it's trucks....

I just received a new set for the L24 from Motorsport... They are bagged from nissan and contain a whole laundry list of various lengths and part numbers combined into one set. There are at least 3 different length studs and a few bolts along with all the nuts and washers. It was pretty expensive as I recall.

Great results are always very satisfying....Goo job!! I will say that I have been through a number of "upgraded" fuel system components....some are not as good as they seem at first. I grant that the original intake may not have been flowing enough air for 6000+RPM torque numbers....but the fuel system should have been able to keep up with most of the powerband. Many times people "upgrade" to a new fuel system when the original system is broken and malfunctioning. Under those circumstances the improvement seems huge...but usually it is not that great. Keep in mind that many folks have to consider the Inspection Nazis once a year. Original equipment has great value to these people. About the 4BBL conversion.... It seems capable of flowing more than enough air and mixing in great quantities of fuel. But it can have some drawbacks.... 1. poor fuel distribution between cylinders....can cause premature wear of the rings on some cylinders...lean detonation on others. Not that Nissan did this right either.... 2. gasoline can pool below the carby and "run" into the engine on hard corners...Auto crossing on a hot day can make this a nightmare. 3. you wont pass inspection in most cities 4. I dont like the feel of the primary/secondary downdraft carbys with these motors. That is subjective...but a good set of S.U.s with tight shafts have a WONDERFUL linear "feel"....very predictable when feathering the throttle in sweepers...or getting power on quickly and smoothly comming out of a turn. I have a set of dual Weber DGV carbys, twin Cannon manifolds, with the jet kits, 2 rebuild kits, and a spare carby brand new in the box. I ran this set up because my SUs were worn out and this seemed like an improvement. This is all sitting on a shelf now. 3 years later I got a fresh set of 4 screw SUs and removed the stupid Weber downdrafts. I spent at least $1500.00 and COUNTLESS man hours trying to make those carbys do what the SUs just do naturally and better. Good luck with the 4BBL conversion...I am interested in how they hold up for you in the long term.

LOL...that assumes your significant other isn't already restrictive enough.

I hate these people who hawk useless junk that can only hurt performance or do nothing at all..... Give me a break....It creates turbulence in the fuel line....and this is supposed to have some chemical effect down the line after the fuel has passed though any number of other turbulent restrictions...including the spray nozzels of the injectors... I bet I can get the same results by driving real fast and "shaking" my fuel tank. As far as the "photo" proof they provide....how about a frame of reference...they can just as well make that claim of soot reduction and really only mean that "we cleaned the paint when we installed the device...and then we took this photo".... The bus pic does not mention that the engine was in too high a gear in the smokey picture...and the clean picture has it in neutral. You can stick one on the end of your Penis to enhance your sperm too.

ummmm....evidently you guys are not looking at the same pics.... The linky shows me 1970-71 round top, 4 screw Hitachi/SU carbys. with the air cleaner....those things are worth $300 if they are indeed in good shape. If he had the N46 manifold they would be worth more.

hard vs soft mounts....hmmmmmmm...... You guys should really keep in mind that cast iron is a lot stiffer than sheet metal..... sheet metal is quite flexible. the whole damn car is made of sheet metal.... If you mount the front of the diff solidly it will simply flex the sheet metal.... I can gaurantee that the car will "tear" before the diff case or the solid mount breaks. If you want to test this I will be happy to hook a cable up to your solidly mounted diff from my 1 ton 4x4. I bet if I floor it the diff will come out with the mount and moustache bar still in one piece. as far as noise is concerned.......You are now flexing the sheet metal in the floor of the car...you can think of your car as a speaker cone...the voice coil is the is the differential and its mount...hard mounts will transfer not only more energy...but also a MUCH wider range of sounds.....Also the rubber in the mount acted as both an insulator AND a dampener....you could add your own damping materials to the inside of the car to reduce noise. A heavy but flexible weight attached to either side of the tunnel would do wonders for noise.... also try putting your original 50lb spare tire back in the well..my 1972 spare fits in with the rubber pressed against the perimeter of the bottom of the well....it is very heavy and flexible so it cuts the noise wayyyy down...it can better balance your car as well.

Look at the procedure for setting up the clutch pedal in your service manual. I had similar problems after reassembling my 1972 a few years back. It turns out that the clutch pedal and the master cylinder rod were not set up correctly....following factory procedures for setting the clearances and pedal height worked like a charm..... as far as the machine shop saying the "resurfacing" was done incorrectly is total B.S.... I have heard this far too often from mechanics who simply did not want to admit they never had a clue how to set pedal height or free play by factory specs. 99.999999999999999% of these clutch problems are caused by half ***, ignorant attempts to set up the pedal height and free play in the system. BUY A SERVICE MANUAL......and demand that it is followed to the letter by your mechanic.

edit: ok already covered

I installed the crankcase evac kit that Mr gasket offers....there is a Moroso kit for twice the money. They are one way valves mounted on an angle cut tube welded into the header collector. They create vacume by venturi effect from exhaust gasses rushing through the collector pipe. I got 2 of the check valves in the kit...I had to replace the first one mounted 3inches off the pipe after only a few thousand miles....I added thinwall tubing and some flare adaptors to place the check valve up high away from heat....The second valve has lasted for 5000 miles soo far and has no signs of quitting. I am currently using the original "flow control valve" mounted on the left inner fender of my 240Z....this valve is a 2 stage relief valve for crankcase vacume. I have the exhaust evac. tube pulling on the top valve cover vent. The PCV valve is connected as usual to the lower crankcase vent...I added one of the oil separators that came in the evac kit to the lower crankcase vent with a 90degree elbow soo that it sits level and drains back into the crankcase. I am routing the small nipple on the lower crankcase vent to the "flow control valve" in the stock configuration. The reason I am using the stock vent system is that it provides a vacume relief for the crankcase. It works in 2 stages...first it pulls vacume on the fuel tank...as vacume builds in the tank the second stage opens and draws air from the atmosphere. Soo far I have no problems...except the darn thing pulls too much air....I am afraid It is going to cause fuel pump problems with anything but a brand new pump. I can hear and feel air rush IN the tank when I pull off the gas cap with the engine running at high idle. The system worked fine with my old restrictive muffler....2.5" exhaust and the muffler had a 1.5" restrictor tube buried inside...I recently added a Dynomax "turbo" muffler with no restrictor. Now the crankcase vent system is really pulling a lot of air. In fact the "flow control valve" cannot flow that much air...at full throttle vacume builds slowly until you let off the pedal. Keep in mind that none of this affects the Manifold vacume...only the crankcase side is affected. I am considering adding a oil separator tank with baffles and a drainback system that combines the various vents and plumbing to one location. I would like to provide a way to "flow" fresh filtered air through the crankcase while maintaining a slight vacume in the crankcase. The current system pulls on both ends of the block and only allows air from the outside through the highly restrictive "flow control valve" (into the lower crankcase vent). I would also like to combine manifold and crankcase vacume(with check valves) in a resivoir to aid the brake booster servo...the cam I am using provides very poor vacume at idle...hard brakes can surprise me in slow traffic sometimes. The brake booster only stores enough for 2 or 3 pushes on the pedal. I would like more reserve. Any ideas would be welcome.

I noticed your pic of the header collector....I installed the same crankcase evac tube in my collector.... I got 2 of the check valves in the kit...I had to replace the first one mounted like yours after only a few thousand miles....I added thinwall tubing and some flare adaptors to place the check valve up high away from heat....The second valve has lasted for 5000 miles soo far and has no signs of quitting. I am insterested in how you intend to plumb your evac system... I am on generation 2 and I need to move on to gen 3 plumbing. I am currently using the original "flow control valve" mounted on the left inner fender of my 240Z....this valve is a 2 stage relief valve for crankcase vacume.

I ran into the same problem when adding a rear swaybar to my 240Z... I used a rear mounted swaybar that pivoted off the rear crossbrace behind the diff. For starters...you really have to get the brackets as high as you can to clear the drive shaft under full compression....And I had to cut the end link spacers to 2 different lengths to compensate for one control arm being convex and the other being concave...about an inch difference..... Like a dummy I tried to measure the difference and cut the spacers different by the thickness of the control arms...Well...that ended up wrong... second attempt was done by trial and error with the car on its wheels and the endinks measured to fit the car as it sat level.

123MPH to stock redline on 205/50/15Z Azenis..The speedo will read 140 @redline ....I think it could get a little higher with larger wheels. It does not need to go any faster...even at track events.

I have installed several camshaft kits...pain in the ass...you really have a lot of time waiting for more lash pads to come in the mail I have a collection of various thickness lash pads now....The cam kits work well on a high reving high compression engine...they just make low comp motors sound cool and idle poorly. I have no idea whether a cam kit would help a Turbo L-6..I think not..the turbo will just blow half your charge out the exhaust during the overlap. I have heard that the P90 hydraulic head are not well supported for parts. I have heard that the Borg Warner trannys are not supported for parts. I would not coat the inside of the intake manifold..It is bbound to come off sometime and ruin you motor. The stock valvetrain is fine I think...you don't need to rev past 7000RPM with the Turbo. You can lighten the rockers and get stainless valves and aluminum keepers if you really want to see 8k on the tach. I have a BSP prepped 240Z...I wind it out to 7k all the time. It pulls hard to 6500...and gradually falls off. I had it well balanced and used all Nissan parts. I have a mild cam installed with stock lift. I am using the original R180 diffs...I like the low ratios for track events...they seem to hold up fine for me. I rebuilt one and installed Phantom Slip traction plates. They are a dime a dozen and I like that... I am using the "B' 4 speed tranny... I love the 4 speeds because they are a dime a dozen...but they have not failed me yet...I ended up with 3 extras for free.

I came within a hair of buying a set of KA-24 flat tops for my current project L-28/E-31/SUs... with a standard L-28 crank the compession was acceptable...but the piston would be almost 2mm below deck with the longer 240 rods...no squish effect.. I have 2 sets of L-24 rods and I was willing to bastardize 2 engines...l28 and l24.... I think I am just going to slap the cammed E-31-(with big valves) on the 1mm oversize flattop L28....I can get away with pump gas I am pretty sure...

You can trust the quality of most of the amp install kits. The red and black power wires are vinyl insulated and hold up well under extreme conditions. The superfat speaker wire with the clear insulation is not rated for UV, oil, or high temp. Do not use speaker wire. A good alternative is low voltage direct burial landscape lighting cable. It is very tough and it is chemical resistant too. Always use multi-strand wires for you automotive needs, stay far far away from natural insulation compounds and silicone insulation. It has a tendancy to split and crack after a few years. Always place a fuse on the battery end of ANY WIRE YOU ADD.....DO NOT EVEN MOCK IT UP until you have a fuse block installed.