technicalninja

Might have a restriction in the metal lines in the tank. If replacing the lines doesn't help might want to check this.

Difficult to clean out of the cooling system. Mixture of bleach and water followed by multiple flushings seems to work best. Messy and nasty. Pretty common occurance. Need to inspect tranny fluid as well as after car is turned off pressure drops off the tranny cooler faster than pressure drops off the cooling system and antifreeze can get into the tranny. BAD BAD BAD

Could be tranny fluid from the cooler in the radiator.

I've done it myself as well but it is a grunt. Much easier and safer to have someone help. Coming off the stand is not so bad (normal strength average man) but going back on is difficult. Two weak people can handle it with ease so you can ask your girlfriend/ Wife is SHE would like to participate in your project. Teenagers work well to- and complain less about the grease.

Yes you do have to drill a new pivot hole and I have found 3 different styles of tower lengths (shift lever ears that pin fits through). The 77-79 trannys had the short ears which cannot be redrilled but are the ones that work with the MSA short shift kit (at least the kit that I have now). the 80-81 trannys had the medium length ears which can accept a 10 mm higher hole, and the 82-83 style which has very long ears and could accept 20 + increase. If you were very-very steady you might be able to drill it on the tranny (tranny will have to be removed from car). The ones I have done were during complete tranny overhauls and the shift tower was removed from tailshaft housing and drilled with a good drill press. Pin fit was as tight as the factory hole. The mod doesn't cost much but "some assembly is required" and I don't think I would remove and dissemble tranny JUST for this mod. awful lot of work (by itself) for the change. Jon- I included my measurements to clarify what I thought was not enough - 10 mm and too much - 25 mm. Yes - there is a thing as to much and for me I think anything over 20 mm will fall into that catagory. This was to help readers visualize the difference and maybe give a starting point for someone else doing the mod. The distance between the pin and cup does mean dick as it controls the total movement in degrees between far ends of the throw. Shortening the upper section does nothing to this ratio although it will affect travel of the knob. The location of the pin in the ears does not change the shift ratio at all and can be anywhere (vertically) that allows the lever to not bottom out against the housing (lever straight up and down) and keeps the tip/nylon cup in the inner rod at the far ends of the travel. I mearly drilled my holes the exact same distance higher that I added to the lower section of the lever. Everything fit fine that way. Although I don't have one (yet!) I would bet that the truck shifter is not more than 10 mm longer that the stock 240/280 unit and IMO 10mm is not enough. I expect that I will have to shorten the upper length to satisfy me. There are definite benefits to using the truck shifter. Done in car and only requires basic tools. No modifications to tranny at all. No welding. Should be cheap as long as you can find a early truck. I have been watching for one for 6 months now. Just like 510s and 240s they appear to be rare now days. Different ways to skin the cat for different people. When I did my first mod I was not aware that a longer shifter which would fit using stock pivot hole was available or I would have tried it first. Due to this site and Jon I have been educated that an easier way does exist. I'm just not sure if it will be a large enough reduction for me. I went out and measured total travel between far ends (3-4) on the MSA kit 2.5 inches. I didn't like the weight of the knob but it sure feels nice to grip. Their kit appeared to be a real Nissan shift lever and Nissan knob (can't imagine what its original application was as I have never seen anything even close to it) and the custom ear extenders which are not a Nissan part. I did check if the 25mm longer MSA shifter would fit the longest ear shift tower and it will not. If you want the 25mm addition you will have to use some kind of extension on the ears.

I have modified 2 shifters now using the method I posted earlier on thread and one of the trannys went into a customers car that had the MSA short shift kit which is now on my 78. The MSA kit increased length to section below pivot by 25MM and shortened the upper section by 10MM and although it is a nice part I believe the change in pattern is too much. It did increase the force required to shift and even has a very heavy knob to help this out. The problem I find most annoying is I sometimes think the shifter is in 3rd when it is actually in 4th and it is slightly disorienting to have to change directions that you were moving your hand in. I haven't had it in the car long and will probably get used to it but it sort of wierd. The two shifters I modified I added 10MM to lower section and did not change upper section at all and although they definitely shortened the shift pattern I felt it was not enough. the next time I do one I will add 15-18MM to lower section and leave upper section alone. this mod requires the long ear variety of the shifter towers (82-83ZX trans). I will be looking out for a truck shifter as this change sounds dirt simple and by shortening the upper section it may well shorten the pattern up enough. One of my customers had an extremely shortened 240 shifter in which most of the upper section was removed and nothing was done to the lower section at all. I hated this set up, you almost had to reach down inside the console hole to reach the shifter. The MSA shifter kit required modification the first time it was installed as the side plates would not tighten up and it had quite a bit of slop in it between the side plates and the shift tower on the tranny. After modification the side plates had to be carefully alined during tightening procedure. Both the truck shifter and my mod do not have this problem as nothing is added to the shift towers.

These combinations regard stock combustion chamber CC N42 Early 240Z 70-mid 72 will lower compression Mid 72-mid 80 compression will not change as this head has same CC as all heads applied to these years. Mid 80-last 83 NA will raise comp to approx 10-1 (flat top pistons) All turbo ZX will raise comp to approx 8.5-1. (dished pistons) Put on an early 240 with the parts you described it will probably produce LESS power that stock set (yes-even with the SUs) up untill revs pass 6000 after which increased flow capabilities will come into play but lack of compression will still restrict total power output. It will make about the same power as the stock 240Z (maybe a little more) but it will have lower torque at all engine speeds below 6 grand. I would expect loss of .5 seconds in 1/4 mile ETs. Yes it will run on any gas you can buy (even cheapest regular) and adding a big cam will only make these problems worse and the cam will be necessary for operation above 6 grand. It will also require a custom balancer and other hi rpm operation mods to increase reliability at these speeds. Just bolting this head on a stock bore 240 will require "eyebrowing" of the cylinders and putting bigger valves in the head may not clear cylinder walls even with extensive mods (valves will hit cylinder walls). This set up you described will work pretty well on a flat top piston 280ZX engine and set up with a proper cam (not the biggest cam that is available) should produce power in the 200-240 range (depending on setup and the tuning abilities of the guy who does the work) and it will definitely work with 95 octane fuel and properly tuned it should work fine on super-unleaded pump gas. I built a customer engine using N42 (ported and worked comb chambers)flat top N54 block/ tripple Webber, small preformance cam, big exhaust and the car now has almost 30,000 miles on engine with no mechanical problems. It will out accelerate a stock LS1 Camero and has gotten as good as 24 mpg. It has only been run on 92/93 pump gas and does not ping but each part was chosen to balance/match the other parts. A better head for a 240Z application is either an E31 or the Maxima head of which much is written on this site. IMHO more investigation is needed on your part. Any performance engine has to be built to a proper plan and the mods need to compliment each other.

I would look for something causing drag between the engine and the transmission which basically results in clutch performance like a user is only depressing clutch half way. Clutch not fully dis-engaging (poorly designed PP) Warped or too thick disc (very rare) Sticking pilot bearing (very common) Mis-alignment of engine-transmission (missing dowel or pin at bell housing) Lack of travel in clutch hydralics (probably not in your case) Bent/damaged clutch release fork (creates lack of travel) Improper TOB carrier (probably not in your case) Improper friction surface height. IE flywheel needs step or flywheel has been cut to much (only seen this once on a Nissan truck but it did effect disengagement). I would lean towards the pilot bushing first. A common misconception is that the pilot needs no lubrication. They are sintered bronze and require "oiling" by placing bushing on your thumb one open end down against thumb, filling the interior with common engine oil until totally full, and slowly apply your other thumb to top pressing oil through bushing. You will actually be able to see oil weep through the walls of the bushing. drain excess oil out of bushing and wipe or blow off. you should not be able to see liquid oil on bushing at install, you are "infusing" oil throughout walls of bushing. I use a wooden dowel to install bushing in crank to keep from mushrooming end. I have used a properly sized socket before and most of the time it worked OK but sometimes it would "ding" the end of bushing. My wooden dowel has never dinged a bushing. "oil" bushing slowly as I once split one by being to hasty- suprised the dog out of me. A slightly damaged pilot might "fix" itself every now and then causing your inconsistent results. Another minor possibility is the step in the flywheel. Yes there is a minor step. Years ago I verified the step by going out to Courtesy Nissan in Dallas and measuring all the new 280Z/ZX flywheels that they had in stock. .006 inch was what I measured. I fully believe that most clutches will work fine on a totally flat flywheel as .006 in is a very small amount and could easily be accounted for in normal clutch wear but a friend of mine (375 HP turbo using standard Nissan trans) who drag raced extensively could not get a clutch to last with out a step in the flywheel and he increased his step to .015 as I remember. His problem was different than yours- he was killing clutches; not having trouble shifting. I also had a customer with a 350,000 mile Nissan truck in which his flywheel had been turned to much moving clutch closer to the engine which caused hard shifting due to lack of travel to disengage clutch. This is the only vehicle I have ever seen this on (20+ years professional import tech). very wierd and hard to diagnose. I had tranny out of truck more than once to find this. Shortly after the clutch/flywheel fiasco his truck started breaking headbolts from age/fatigue and he finially took my advice and replaced it with a newer Nissan truck. The low oil level you described is not good- If the tranny shop did the install shame on them!. I would drain oil into clean pan and really look at oil for debris. Nearly every tranny that I have found problems with had crap in the oil. After draining trans stick your finger into drain hole and feel around floor of case (that you can get to) for debris that didn't come out with oil. Any of the oils mentioned in earlier posts should allow tranny to shift fine (including what you think is in it now). Some of the special oils can smooth tranny operation (and lower tempatures-important for track use) but none of them will overcome an actual problem Hope this helps Rick

I just used some Saturn exhaust studs and nuts (92 SL2 twincam engine) to install a MS header on a customer car. Perfect length with cool little inverted Torx heads for ease of install. Black oxide coated. Nuts are 13 mm class 4 (metal self locking) and will probably pull the studs out when removed many years from now but will not loosen up. Would have rather had 12mm heads but I was able to get to all except the inner nuts on #1 and 6 with a socket and the two I couldn't reach with socket were accessable to a wrench. Worked great. Got into locking portion of nut about 2.5 turns before tightening to the manifold. Full retail at Saturn: studs .99 nuts .79. I ordered 11 of each and did all locations on manifold. Was going to buy studs from Pallnet but he got into a Hurricane right about the time I needed them. I am sure his stuff is higher quality than the Saturn parts but the Saturn stuff fit far better than I expected. Was cheap and easy to get also.

Compression is fine, All comp gauges vary somewhat and one gauge might show 150 where another would show 165 and yet another might be at 125. I have verified this strange fact by testing all the gauges in a dealership (more than 10 mechanics/gauge sets in test). Even had large variations between gauges made by one source (Snap-On, not a cheap source). What I look for is readings close together. Your engine has a smaller variation factor than most engines, even freshly rebuilt stuff. Doesn't appear you have engine or ignition system issues but ignition patterns should be looked at on a scope to verify ignition is actually working properly as some problems cannot be diagnosed by part inspection. I would look to an injector/injector pattern problem next. Also might be vac leak issue.

Bad vac leak in rear manifold might cause problem but should also have other symptoms which would be obvious to you. Might have something in fuel line to jet or jet itself. Some (late 71/72 carbs) have different float mounting legs and as such have two different settings (and different length needle valves). I seem to remember that the long set goes on rear carb but I may be wrong. An exhaust back pressure test might help decide if the exhaust is restricted which can poorly effect high speed/load drivability. Drill and tap exhaust pipe for 1/8 pipe- Brass fitting- 8' vac hose- standard low pressure F.P. gauge. For N/A anything above 1.2 psig is not real good, above 2 will seriously effect power, and good system should be .5 or lower. Verify that mechanical and vac advance is working. Swap back three plugs with the front ones. Verify fuel pressure while driving (tape gauge to window and check at speed) Verify float vent is open and any line attached is open to atmospheric pressure (might have gotten plugged off when the emissions were removed) Verify that airfilter housing does not restrict vent to vac chamber (pot). Snap throttle while holding you finger lightly against piston to gauge piston load reaction. If the back carb is not opening as much (or opening faster) you will be able to "feel" the difference. I would guess either the rear carb piston is reacting differently than the front or you have a reduction of fuel flow at rear jet. Might be smart to run FP test line from rear carb fuel inlet. Valves badly out of adjustment might cause these symtoms as well. Hope this helps Rick

Don't have to take the lower ones off, just loosen up a couple of turns and pull manifold straight up. The lower stud/nut are also used for sealing the exh man and spans between the two manifolds with a big thick curved washer. much easier to remove and instal the nuts/washers when intake is out of the way.

The 83 Head (p79) has round exhaust but the 240Z head (E31/E88 ) has square exhaust and the exhaust manifold/header that is on the car now may or may not work with the P79 head. Headers seem to be more finicky about this than the orig exh manifolds. Will need to look a sealing of exhaust carefully. All the FI heads that I have seen (N42/47, P79/90) have both the 240Z and the 280Z intake bolt patterns machined in the head. The intake should bolt up with no problems. T-stat housing mount is the same on all L-series.

You can make a version of a thread chaser with a good used gland nut by grooving it. Make 4-6 straight cuts perpendicular to the threads evenly spaced around the nut. You can use a hacksaw/file but it is important to keep the edges straight and "clean". Each grove makes a little cutting tooth on each thread and the grooves allow cuttings to have somewhere to go. I like to use a new dremel cutting wheel as you can create truly sharp edges (can't allow tool to skip across nut when cutting-hold very tightly).You can taper the first few threads with a flat file to ease starting of the tool in the damaged housing. I have never heated and quenched the tools I made but it sounds like a wonderful idea. I think it would make the tool a permanet addition instead of a one or two use tool. I have fixed badly damaged threads in both steel and aluminum using this method but I would be critical of a repair to a strut tube. If I could get one I would use a good housing over one with wobbled out thread section as the gland nut will loosen up and come out of the housing if it has any play at all. I have a pair of early housings which are perfect, been cleaned/bead blasted and painted but I am not willing to sell just one. Jerry@ALLZs here in Ft. Worth might be a source for a single unit. Rick

TonyDs is correct that the later GR starter was applied for F.I. starting glitches but it created a starter with all sorts of torque that is good enough that most of the high end GR starters for wild V8s are based on this unit even to the point that many of them are actual Nippon-Denso and Hitachi units. Z trannys from mid 71 through late 83 will interchange with basically no major issues. exceptions are 70-mid 71 removable bell housing and ZX Turbo 5spds (Borg-Warners). All 70-83 z starters will interchange with no issues at all. If I had to purchase a rebuilt one I would definitely buy a GR style but using any style from any year will work fine. Only mod you will have to do to change over to a mid 80-83 NA ZX tranny is to put the speedometer drive gear from you original tranny in the later housing. The housings are different between early and late. You need the correct housing for the tranny but the inner gears are interchangable after removing a small roll pin. You should replace small seal inside housing when you have it apart (Nissan dealer part only) Ways to tell if your looking at the late ZX tranny out of the car. bolt which holds speedo drive housing in tranny is on a pad which sticks down off to the tail shaft housing. Earlier trannys had it going into case above drive. 2 10 mm threaded holes in lower section of bellhousing for engine braces. Reverse lock out mechanism- small diamond shaped plate on drivers side of tailshaft housing just above and forward of tranny mount flange. Earlier trannys didn't have this at all. ears for shift lever are longer- even though pivot hole is same height. You can redrill this hole higher and lengthen shift lever below pivot to make a "short shifter". The last production trannys had extremly long shift lever ears. To identify a 280ZX that should have the late tranny the car will be produced after about 5-80 (vin plate in driver door jamb) or on model identification plate (in engine compartment) you can find RC 3.9 embossed on bottom line of information. This is the rear gear ratio and the rear end will bolt right in your car as well as the tranny which is an excellent quick preformance mod for your car as well. The car will also have an F54 engine block in it (embossed in lower driver's side of the block). If you are planning on keeping the original 3.54 rear gear in your car the earlier 5 speed will work fine as it has identical 1-4 ratios as the original 4 speed. It mearly adds a .864 5th gear. the later tranny has taller 1st and 2nd gears and its overdrive is taller at .745 which will help lower engine rpm at cruise speeds. The late tranny running through the original 3.54 gears will launch a little softer and have a lower rpm at cruise speeds which might help your hiway fuel mileage. The early 5 spd running through the late 3.9 rear end will have a first gear that is so short that you will tend to use second gear to start off (when your not "on it"). Full throttle launch in first gear is less than 2 seconds before you have to shift to second (motor in proper tune). My 78 is currently set up this way and it can be fun (extreme hole shots) but I would rather have the later tranny. The drive shaft you have will work fine with any of the 5 speeds -exception being the B-G Turbo 5 spd.

All 81 +up ZX use the F54 block and they should be the same turbo or non-turbo. You should be able to find one down in Houston no problem. The earlier 280Z and ZX block will bolt up to everything major but it has a few differences. The cylinders have waterjackets between them and this might make the earlier block slightley more prone to cylinder wall movement. This is faily important if you were building something with a bore of 89mm and up but this should NOT be a problem with the stock bore. The earlier block will not have a spot for the detonation sensor and tranny brace peices. The thing that is the most important IMO is the tranny braces as they do make this area stronger. I would use a F54 block unless it was impossible to get one reasonably. I have a very good 82 F54 turbo block that I was starting a project motor with. It has no damage anywhere and it's bores run .002-.0025 over stock piston size. The bores have less that .0004 taper and average .0005 out-of- round. These clearances are within specs in the Nissan SM. It has been pre-cleaned and partially polished in the crankcase (about 60% done). All bolt holes are flawless and have been carefully cleaned with taps. I have rough honed the bores (with flat stones) and it is ready for it's final machine shop visit. I was going to have it vatted, decked, and platuea honed. The main galley has been fitted with pipe plugs. I wasn't planning on selling it but it could be bought or traded for? It will make a good motor IMO (ASE Master Tech- Master Machinist, 20+years) It is mounted on an engine stand right now and you are welcome to make the clearance checks yourself. I believe you should be able to find a complete short block somewhere in Houston between 100-200 used and if you are lucky it will rebuild standard but if you cannot I am up in Ft. Worth. Rick

Spoken with more than just Earnie at Konig. If it is a scam it is a complex one which involves NASA and GrassRoots Motorsports. The people at Konig sounded like the responce to this offer is quite business disrupting for them. I believe its real and am waiting for my wheels (have not received them yet and wouldn't be suprised if it takes Konig quite a while to fill all of the orders.) Earnie spoke of the deal lasting for a year but it wouldn't suprise me if it was shut down sooner.

The cam tower shims are used to correct cam retardation as the head gets thinner when its milled. As the cam centerline drops toward the crank it retards timing; the shims bring it back up to proper specs. The shims are not built to decrease chain slop although they can help with it anyway. In many cases retarding cam timing is the way to go as it moves the torque peak up in the RPM range which can make better power (especially in small displacement engines like the Z). I also believe the gear set up will provide better control of the chain at high speed but it will require periodic adjustment and if it is out of adjustment it will either create great wear on timing componets (to tight) or allow more slop than the stock chain set up (to loose). I would be suprised if this piece would increase horsepower in a measurable amount and the other limitations of the L-series perclude the use of the engine at speeds which the stock timing chain parts can withstand. The timing set up has not been the limiting factor on L-series engines. Its neat looking but cost $$$, won't help power much, creates more places for oil leaks, and increases maintenance. Not for me. If I was going to this amount of trouble for ultra hi rpm use I would be using a different engine family which has a 4 valve cross flow head like the RB series motors.

I would not slide a pair of seals in without removing the rear main cap. Most of the sealant would get wiped off, the area that is most important would get the least amount of sealant, and it is not possible to clean the old sealer out of the area without removing the rear main cap. I would give it a 50% chance of sealing your leak if you just slid another set of seals in. Also this way does not allow you to apply sealer between the cap and block which I believe is more important than the rubber seals themselves. After the pan is removed it is not all that difficult to remove the rear main cap but it will take a special tool. A small slide hammer with an adaptor to 8x1.25 mm thread. My slide hammer is adapted to a pair of Vise Grips which I lock on a bolt that I have threaded into the rear main cap. Works great!. After removing the main bolts on rear cap a few STRAIGHT wacks on the slide hammer will remove cap. Some people have probably removed this cap by using prybars but I don't recomend it. Carefully tapping the cap back into the block can be done with a small hammer and it helps to have a couple of long threaded studs to screw into the bolt holes. These studs help giude the cap back into position. The job can be done without them but they make it easier (especially up side down in the car). Now, If this was my car I would remove engine, mount on stand, and fix it properly for one more time ONLY. If my memory serves me right you had a less-than-steller mechanic do your last rear main seal and the oil leak is a problem that has re-occured more than once. I would re-seal rear main cap, replace rear main seal, inspect seal register (surface) on the crank and polish or "Micro-Sleeve" it, and reseal the pan without the oily mess. I would also seal the front of the tranny while I was at it. I understand your living arrangements limit you to what you can do to your car. I feel your pain. Always remember- oil is cheap!, As long as it is not leaking onto something than could be damaged by it it will do no harm and protects against rust! My dumpster-on-wheels 95 Grand Voyager has leaked badly since I bought it 4 years ago. It's bad enough now that I will not park in friend's driveways and I will be fixing it sooner rather than later but I have driven it 50K plus miles like this. As long as its not getting on the clutch and its' not sliming the bottom of the car badly I might not fix it. How often do you have to add oil? Does tha car leave a puddle every time you park it? You can also look up into the PP area through the clutch fork hole in the tranny. Just peel the rubber boot out of the way.

It's possible that the needles are installed to deep in the pistons. The shoulder should be flush with the bottom of the piston not flush with the groove it sits in. Loosen needle, place metal ruler across bottom of piston (across the bore - parallel to the throttle shaft). Pull needle down until shoulder hits ruler; tighen and check how needle goes into jet. Is it centered all the way down?. Some times rotating needle in piston can help an out-of-align situation. I have also seen the jets worn on one side (by a bent needle maybe?) that required replacement. I have also found a lot of "HOT" needles (especially ones that have been modified) are not that hot at all for normal street driving. If you still have the original needles put them back in and see how it does. I have found minor tweaking of the stock needles position in the piston was a far better way to "tune" the carbs to the engine. Put mixture adjustment nuts in the middle of their travel and move needles around until you find the center of the "sweet range" the use nuts for fine adjustment. This is all dependant on and related to float level. Make sure it is right before messing with needles. New needles and jets (just stock stuff) may make you job easier. Your set up shouldn't need much change from stock. These carbs were set up fairly rich from the factory (Much more so than a 280's F.I.) and all carbs meter fuel dependant on airflow and have a CFM range where they are most efficient. If you put a higher CFM engine behind them their sweet spot moves down in RPM. They still meter fuel just fine and their limitations are only noticed in high RPM/high load range. I think the stock S.U.s are a great size for a mild 280 (under 7000 rpm) and will give better low range drivability that ANY other carb currently available. F.I. will beat them but not by a large factor. Rick

When I install a rear main cap I lightly coat a section of the sides and out to the seal bore with Pookie (Aviation form a gasket non-drying-Permetex) to help this spot seal properly. The factory S.M. covers this as well. You have to keep it away from the bearing and install the side seals properly. Many aftermarket gasket kits have piss-poor side seals which are hard to install properly (they don't go all the way down because they are to thick). I try to use the factory ones if I can. Another place that can leak is the rear main galley plug which is beside the starter about 5" up the block. These only leak if they have been taken out and replaced with a pipe plug (done during a engine rebuild to allow access to galley). I have never seen a leak from a factory plug but a leaking one of these pipe plugs cost me a rear main seal job followed by 2 oil pan/rear main cap jobs followed by ripping tranny out one more time to fix leaking plug. All done in the chassis. Really makes you look "good" to your customers. By the last tranny removal I was beating book time by 70%. Practice makes perfect! Anger gives you energy! Bet your becoming pretty quick with the oilpan job on the Z. (Sorry- couldn't help myself) Your leak could be either as they both come out the same spot. If you are still running the original plug I would focus on the rear main cap first. Hey-you can install that last main-bearing pair (if you kept them) while your doing this. Sent you a P.M. Did you get it? Rick

Well, you post got me to thinking: If I was to attempt this what would be the easiest setup? I'd start with a P90a head which already has hydros and I would build 6 "special" lifters. I believe the best valve position would be intake closed and exhaust open at during a complete 4 cycle "event". I have done no research but it seems to me that you would not want any wierd dynamic pulses from the deactivated cylinders getting back in to the intake as it would disrupt normal flow to the other cylinders. This leaves the exhaust valve as the only place to perform the compression bleed off. My intake lifters would allow collapse during deactivation to the point that the cam could rotate a full 360 degrees with out contacting the rocker. The ehaust lifter would extend enough during deactivation to keep the valve off the seat at all times. Expected problems with intake side- rocker falling off valve tip and lifter causing complete upper end failure when it gets into the other valves. Some form of bracket/spring may be able to address this problem. Exhaust side- Clearance issues around TDC between piston and valve and valve seal to retainer clearance at max cam lift. The P90 head has the highest valve position of any of the heads and may allow clearance with out putting valve pockets in the piston. The location of the L-series lifter would make plumbing easy as you would just drill from the outside into the lifter "bore". You would need a high pressure hydralic system, some sort of electro-hydralic actuator, and a proper controller. And you may have issues that you did not expect: I recently took a customer core engine apart to scavenge usable parts. This engine had approx 60,000 miles on a "full" rebuild by a less than perfect shop. The customer drove this engine for quite awhile with two badly burned exhaust valves and the bores that had the bad valves were destroyed. It would have require a .040 cut (1.0 mm) just to clean them up. The other four bores were fine and could have been refreshed with just a set of rings. Fuel and spark were not cut off in this case but compression sure was. Having your front 3 cylinders wear at different rates that the back three will lead to reliability issues down the road. This could be solved by also plumbing the front 3 for a second system and alternate front to rear on some time based formula. You posted about someone else's actuators being expensive. If I was seriously thinking about doing this to any engine that didn't originally have such a system I would buget $50,000 and be happy if I ended up with just 1 functional system. Basically having the project at the point it could be used to model a final design for production. This is parts and machine work buget only. I would be doing all of the work myself. Having something like this done by a competent design and manufactoring company would be incredibley expensive. One final note: We all feel foolish at some time so don't feel bad about posting your questions. Just recently I was helping a friend put a spoiler on and we needed to "machine" a screw mounting surface bore in a part with the location being down a long curved "wing" section. After 30 minutes messing with the tools I had (die grinder,Dremel, variety of drills) we were headed to the local Home Depot to purchase a Dremel flex shaft kit when my 15 year old son took one look at our problem and said "why don't you take the bit out of the Dremel, put the bit through your hole, reattach the Dremel on the outside of the part and use the back side of the bit to grind your flat spot?" My friend and I just looked at each other for a few seconds and I said "damn- from the mouths of babes- wish you'd said that about 30 minutes ago". It worked absolutely perfect. Bryan (my son) sure makes me proud at times. It was still a "newbie" who saw through a problem that had two "supposedly intelligent" techs stumped . Sometimes even the most experienced people make "foolish" mistakes or don't understand a system as well as they thought. Welcome to the club. This is the best way to learn. When a bit of knowledge cost you money, blood, or "face" you will remember it better. least-wise I do. Reading a column on the Honda Odyssey in GRM it appears that Honda's system is good for about a 10% increase in fuel economy and the system requires the interior sound system to broadcast "anti-noise" during operation to mask excess noise from the rattling vibrating 3 cyl . Seems pretty complicated for 10% increase to me. Also looks like a drivability nightmare for the Honda techs some time down the road. Good luck Rick

Welcome CybrStuff, I lurked for a while before I posted as well. Your ideas have great merit as a theroetical challenge and research and development project, but at the end you will find the process you go through may develop you more than it helps the Z in the gas mileage department. If you successfully develop you own cylinder de-activation system I bet you will be able to land a design job at any of the major manufactors. The very biggest problem you will have to overcome is being able to deactivate at least one of the valves in each cylinder you plan to deactivate. The compression stroke on a deactivated cylinder pushes against the rotating crankshaft on every deactivation cycle. This reverse load occures (at least on an even-fire six) exactly between each power stroke which is not a good spot to lose power. The even fire (120 degrees between power strokes) engine will be getting a power stroke every 240 degrees when operating in 3 cyl mode. Suzuki (and maybe others) built a few small 3 cyl engines in the late 80s-mid 90s and these were little vibrating beasts and were not successful. I don't believe any 3 cyl are being built today but I may be wrong. I hated them when I made my living wrenching. These cars had problems with out the extra backward push that a deactivated 6 will have. You have to address this or your 6 in deactivated mode will get worse gas mileage than if the engine were run normally. Look to Honda's deactivation system for ideas. Dealing with the fuel and spark is child's play compared to dealing with the valvetrain. Late model BMW V8s have a truely innovated design which controls lift well enough to allow the engine to have an open intake (like a deisel) with no throttle body at all. This engine would allow true cylinder deactivation with software alone. All the hard parts are already there. The BMW may have a deactivation mode, seems silly not to. You will need to design motor mounts in which a ball type seat rests on a silicone "pillow" in a spherical housing. If the engine is a high power unit these mounts will need to be made strong. The tranny mount may need to be addressed as well. Idle quality will be vastly improved if you run a very heavy flywheel and it might be benificial to have the additional weight added at very specific spots around the perimeter of the flywheel (I'd guess the spots would be at 120 degree locations). Performance would not appreciate this heaver peice. For evenly spaced power strokes you will need to isolate either the first or last three cylinders. This makes controling the throttles some what easier to develop. I would look to Porsche flat six stuff for your intake. And finally what could you expect to save over the life of the car in fuel cost if you developed a truly efficient system? Allowing- A well tuned hi-performace Z should be able to hit 25 MPG normally Your system realizes 25% improvement in fuel mileage overall (may be overly optimistic). Fuel averages 2.50 a gallon for the duration of the "test" (this also may be overly optimistic) In 100,000 miles you will save $2000. As long as the system has ZERO maintenace cost and never breaks down. On the bright side: After gaining all the abilities you will need for this project you will be a hot commodity in the engine control design engineer field and be able to afford a new BMW 6 or 7 series. This will cause you to use the Datsun only for special events and you may have a hard time putting 100,000 miles on it anyway so " Your actual savings may be less" Theoretical discuss is great. It is the beginning of each new technological "breakthrough" we humans have experienced. It is what drives expansion. Try to never let it die within you, even when a crusty old-timer like me brings up reasons why something should not be attempted,-even if the reasons are good. Sooner or later you'll think up something that no one else has. I would not waste a significant amount of time on a project like this as the economical benefits are not high enough for me but it is a complete valid project just for its technical merit. Welcome to the board Rick

I forgot to include my opnion of "normal" RTV. I hate the stuff. I bet my failure rate with red,blue,black, clear or any other color than the grey is 50%. Thats 1 out of 2 jobs having to be redone at my expense (I made my living as a mechanic not so long ago). This is a totally un-acceptable ratio. It also reduces your customer's opinion of you. I DO NOT use anything but the grey in an automotive application. I will use the clear and black for house projects. This is just my opinion, others may have better results than me and as I haven't used any other color in many years the formulas may have been updated for the better. I am set in my ways and will not try the others again as long as the grey is available. The grey also smells different than the rest. I think it sort of smells like a leather shop. the others just smell like chemicals. The grey drys different than the rest. I describe the grey as RTV with super glue mixed in. The grey sticks far better than any other color. This make cleaning the grey off of a part much harder than the other colors, they sort of peel away from the surface, the grey has to be mechanically removed with tools (razor blade, scotch- brite pads). Sent you a p.m. Rick

Been messing with early Zs for 23 years. All years came with shoulder harness installed. Fixed belt in 70-72 hard to adjust and constantly falling out of the hole in the lap belt (its supposed to be removable but it removes itself far to often and is a pain to constantly re-attach). Little retractors that mounted on side roof panel above quarter windows for 73 and early 74. late 74 and on big retactors mounted on strut tower tops. The 74-78 set ups work the best but are somewhat difficult to mount on an earlier car as they don't have the mounting "flange" built into the tower.