Royce

hmsports, I think that would only work with a locked diff or maybe posi, would require you to spin both rear wheels in the same direction!? I have just posted something similar that I have used with good success in the "Transmission ratios and suggested rear gears" thread. I got it from www.zhome.com in the technical articles. Hope it helps!

Hallaian42, From what you describe most likely you have a 280Z 5-speed. I say this because I have one and the drop in revs from 4th to 5th is only about 400-600RPM at freeway speeds. It doesn't feel like they drop much at all if you are working through the gears as you accelerate. If you are revving as much as you think you are than your diff was probably also changed to a lower rear end, higher ratio (3.9 or 4.11). There is an easy way to tell what your diff ratio is. Jack up your car from one side so that one rear tire is off the ground and the other is still on the ground. Support the car on jack stands, but you knew that, and put the car in neutral. Mark a visible spot on the drive shaft and on the tire that is off the ground. While some turns the tire 10 times count the number of rotations of the drive shaft. I think the relationships are: rotations..ratio ..16....3.36 ..17....3.54 ..18....3.7 ..19....3.9 ..20....4.11 etc. There is a technical writeup on this method at www.zhome.com under "z technical library"/"Index of technical articles"/"How to determine what ratio a specific differential contains" by Ross Corrigan. Then once you determine your diff ratio, you can go to http://www.geocities.com/z_design_studio/ and plug in your diff ratio, trans "77-79 Factory Five Speed" is a preset, and your tire sizes and it will calculate for you what your RPM is at various MPH. So you can find out what your RPM is at 65MPH without a tach. Have fun!

First, a 4.11 diff would make your car rev more on the highway, assuming you do have a stock rear end. Going to a R200 will provide you a potentially bullet prof diff but would also add somewhere close to 20lbs to the weight of your car. Not to mention it will require a little more work to swap in than another R180. It isn't hard but it is something to be aware of. Second, would be good to know more about the car! What do you consider "high RPMs???" Ex. 4000RPM @ 75MPH What 5 speed do you have now or how much do the revs drop when cruising and 65MPH? EX. 500 or 1000 RPM. What size tires do you have and are you planning to change your tire size? I have a hard time thinking your RPM would be that high at freeways speeds unless your diff was changed, your tires are very small and low profile or you are used to driving a V8 that runs down the freeway at 2500RPM. Have fun!

I have known of at least three 240Z's that had a single "dim" headlight that was fixed by taking out the fuse and tightening the fuse holders by bending them together slightly. While your at it you may as well tighten the rest of the fuse holders too. If you are going to spend much time playing in your fuse box you should disconnect your battery, just in case, and be careful not to sqeeze them very hard. You don't want to break them! If tightening the fuse holders doesn't work, I would replace the fuse. Remember how old they might be. Old fuses can look fine and still not work very well. Then, disconnect the leads going to the light and put a test light or better yet a meter and see if there is a difference between the "good" side and the "dim" side. This will tell you if you need a new bulb or if the problem is up stream. Remember start with what is easy and cheap and work from there. Have fun!

Keep it down to the legal speed limit and it should stop leaking! They all leak a little, but will be likely to leak more if you are driving higher speeds and/or if the fluid level is too high. Did you fill it with the car level or with only the rear up in the air? This is typically not something to be concerned about. If yours is leaking heavily you might want to put a long tube with a catch can at the end. Lots of racers do this to keep fluid from leaking on the track. Not a bad idea to check the fluid level once a year. If you drive the car hard wouldn't be a bad idea to change the diff fluid once a year or so as well. Same goes for the trans, breaks, coolant oh and engine(of course this should be changed more than once a year if hard driving). Have fun!

Dan, How much did the pistons cost? Do you know how much rear wheel HP/torque your motor puts out? I certainly don't have anything against the stroker setup, I was just thinking of building the motor the other way around. Build the top end first because a good top end will make any L6 a lot better and then go after the bottom end. Regardless of whether the bottom end is a stock L24, a 10:1 compression stroker L28 with custom pistons or a 10:1 stock crank/flattop piston L28 it will really sing with modifications to head and exhaust. Since a F54 L28 could be bought for about $100 it wouldn't be very much more to upgrade there. But if the budget is more open up front then I could see how it would probably save money(cam choice, etc.) in the long run to start with the bottom end and then build the top end from there. I love my family but they sure have cut into the Z budget! ;-) Have fun!

stratcat asked if it was a ZX motor. You cannot tell from the pictures, the way to tell is that there will be a casting number on the manifold side of engine near the oil pan and the motor mount. It will either say N42 or F54. Have fun!

Oops, sorry John I misspelled your last name! John Coffey is a contributor here and on other Z discussion groups. Here recently mentioned his 305HP motor for his 240Z on the IZCC group and I thought maybe I could get him to let us know more about the engine design for his hot rod Datsun L6. Don't know if he will want to tell all his performance secrets or how much he paid for his motor but I am willing to guess it doesn't involve a diesel crank and was more than 10K for the block and head alone. Are you watching this conversation John?

grantman240z, I was looking through some documentation last night and was suprised to see that the L6 engines produced more HP while the V6 Z31 engines produced more torgue. I understand that it was needed due to the extra weight they had to drag around but I have always thought the L6 would be the torque monsters. 71datsun240z, There are lots of places to find a good F54 L28 block with flattop pistons. In fact I would think it would be much cheaper and much easier to find than a L28d crank. I bet if you told us where on the planet you lived someone might be able to chime in with their favorite junk yard are engine source that would be close to you. If you use a stock F54 L28 N/A block, which came with flattop pistons, with a stock early head- E31, E88, N42 or N47(has different exhaust ports.) you will greatly increase your compression (just over 10:1 I believe) over stock which gives you the potential for more torque/HP. The change itself may not help a lot until you make other changes to take advantage of this increase in compression. Going from memory here so don't remember if it is necessary to cut into piston or block to allow for valves to open completely. A higher compression engine responds better to other modifications- bigger , larger valves, more aggressive cam, exhaust.and ignition. On the other hand I am pretty sure if you want to go with the L28D crank with a stock L24 bore you will end up somewhere in the same 2.8l area. If you bore the block out to it's max I think the combo will give you approx. 3.2l. I am going from memory and haven't done the math recently so corrections are welcome. But you will not be able to use both your stock L24 rods and pistons or the increased stroke will try to run your pistons through the head. Again, this engine setup alone will not give you tons more torque/HP but will respond better than a stock L24 to other modifications. I apologise that most of this is information regurgitated from my fussy memory. Hopefully someone else can fill in with details, or I'll try to come back with more factual numbers after doing some research. Maybe John Coffee can give us some of the specifications- bore, stroke, block, head, compression, etc of his 305HP Sunbelt L6 engine!? Hope it helps!

FYI, last time I talked to Rebello they felt that 40mm carbs are only good for show on a stock motor. They recommended triple 44's or 45's minimum for a modified Z motor. I am not familiar with the diesel crank setup but I do think with whatever crank you deside to use the F54 280ZX L28 block that 2manyZ's recommended is a good choice. Given the choice I also prefer the ZX 5-speed because I feel the ratios better compliment each other. Have fun!

The DGV's fit on a stock Datsun Z manifold. I would guess you have a N36 manifold that would be perfect for some early SU dome top carbs. Have fun!

I agree with 2manyZ's they don't look stock! For example where is the strap handle on the passenger door panel. The one that WGHungerford posted looks like an original panel. Have fun!

The way I understand it is any of the first generation Z ('70-'78) heads combined with the F54 N/A block (which came with flattop pistons) will give you more compression (10+ if I remember correctly) then any second generation ('79-'83) head will with the same block. You can get high compression with the P90 series heads but you will have to do considerable milling and then shim the cam towers to get the cam geometry correct. From what I have heard it can work very well but it takes a lot of developement (time and $$$) to get it right. That's what I have heard from the handful of people that have done it. Sorry, no first hand experience but it makes sense if you look at the specs of the different blocks and heads which are documented on several sites on the web. The engine that Rebello built me 10 years ago is a N42 L28 block with stock stroke bored to 2900cc with 240 rods (which are longer than 280) and custom short dished pistons, to bring the compression ratio back to 93 octane street gas specs. Then they used my E88 head but upgraded the valve seats and guides to hardened steel and added 280 valves. I requested a street cam which I feel has limited the power curve to below 6k RPM. I installed it in my car with all other stock manifolds and carbs which probably isn't helping the power end of the scale either. So I probably don't have much more than stock HP but it has noticably more torque than a stock L24. I am considering upgrading the cam, exhaust, and ignition to realize it's full potential but my conservative setup is probably why it has lasted me so many years. From what I understand these days Rebello is building their current evolution of the long rod motor using F54 L28 blocks bored to 3.0l with stock stroke or 3.3l with diesel crank, 240 rods, custom short pistons with a modified (depending on budget) N42 head. They claim these motors are producing between 225 - 275HP with SU carbs and wouldn't doubt it. I think that unless your head is wharped or otherwise damaged in some way you would probably be better off having it developed further than start over again. If you change from stock dished pistons to flattop pistons you will have a high compression hot rod motor for sure. That's my opinion! I am open to hearing what other have to say on this topic because after 13 years of good service I am starting to plan my next motor. This one may not survive the abuse of my right foot much longer! Have fun!

The one with the most time and $$$ put into it! Really!!! Of course it depends on your definition of performance? Here is my qualified answer open for discussion, since I really haven't played around with all the different combos myself. For a budget swap into a US naturally aspirated (N/A) 240Z or 260Z, my vote goes to the N42 because it is more widely available(lots of '75 - '76 280Z built), came ready for unleaded fuel with hardened valve seats and guides(which last way longer too!), fits the widest range of Z applications with square exhaust ports, and has the best compromise of compression and flow characteristics. Shave it a little and it is as good if not better than a E31. Finding a good E31 can be like chasing a ghost and if you find a good one at a reasonable price you will still want to change the valves and the cam. With the P series heads, unless you are swapping over the complete F54 block with the head or going with a Turbo or Supercharger the P79 & P90 series heads require to much developement(read $$$) to get good compression on a N/A L24, L26 or N42 block L28. On paper the hot ticket would be stock F54 L28 N/A block (which had flat top pistons) and N42 head. Then add some cam work, some polishing and things would be getting really interesting. Milage may vary! Making a fast car is just a function of time and money! Who's next?

Hi Owen, I have a urethane airdam and it is not ridgid and I would not be surprised to find out it distorts a little at speed. However, I am sure I could drill some holes at the bottom and add some supports to avoid this. A friend has a fiberglass airdam on his Z and is having a hard time repairing cracks. I would probably be on my third airdam if mine where fiberglass. Sorry, don't know anything specifically about the JC Whitney Z airdam. Have fun!

Hmmm... I'll have to take a look at the casting numbers on the E88's I have. Regarding the valves. My E88 had been fitted with 280Z valves. I believe it is relatively simple machine work because if I remember correctly the original smaller valve seats can be machined to fit the larger valves. In other words they don't have to change the head itself. But probably best to check with Rebello or another Z engine builder to be sure. Have fun!

Time to stir the pot a little. What is an E88 head? I have heard conversations from respected Z folk that there are actually 4 different E88 heads on US model Z cars! Here is the way it was explained to me (corrections are welcome). Heads with the E88 stamped on them started around 01/71 with the series II 240Z(or late '71 model.) This head is supposed to have the same combustion chamber as the E31. Then, in 09/71 with the series III 240Z('72 model year) the combustion chamber was changed to slightly lower compression design. Next, with '73 model year the E88 head was further designed for lower emissions and finally in '74 larger exhaust valves, same size as 280Z, were put into the E88 head. I do have several of the E88 heads on spare engines but have yet to take them appart to see if I can document any noticable differences. I myself have a hard time believing there are 4 E88 heads but have found documentation of at least 2 different E88 designs. So which Z head to use- E31, E88, N42, N47, P79, P90 or P90A. Did I miss any? First, unless you plan on changing to round port exhaust you can rule out the N47 and P79. Next it depends on which block/pistons you will be using. If using 240, 260, 280Z block with stock crank, rod piston setup then forget the P90 & P90A unless you are going to run a turbo because the compression would be too low for performance driving. So that leaves the E31, E88 or N42. None of these are a "bad" choice, with the exception being the emissions designed E88. But trying to identify an E88 head may be a challenge. So that narrows us down to E31 vs. N42. The E31 is supposed to benefit from a slightly higher compression combustion chamber design but because of age and limited quantity finding one in good condition can be difficult and expensive. The N42 is slightly lower compression combustion chamber design but unlike the E31 and early E88 it has larger exhaust valves and came with hardened valve seats and guides for running unleaded fuel. Plus, there are lots more available and you can shave them to get higher compression if that is desired. Bottom line, I am guessing that the difference between the heads may be +/- 10 HP. Unless you head is damaged you would probably get more by setting your valves correctly, getting a valve job, changing the cam, recurving your distributor or porting and polishing your head and intake manifold then by searching for a new head. But it really depends on your desired results and how much $$$ you want to spend. Sorry for the long post! I hope it makes sense and is helpful!

The beauty of the internet is that you can reach so many people in around the world. But sometimes it can also be a curse! Bummer about the wheels! Sounds like you are going to need something like 20mm spacers or maybe you can go with a more narrow tire. I would suggest you stay away from generic wheel spacer if you plan on driving the car hard. Best to go to a machine shop and have them make you some good quality spacers. Depending on how wide the spacers are you may also consider upgrading to high grade wheel studs, like ARP. Then if the wheels are for front wheel drive which I doubt because you wouldn't be able to drive at all, then you would want a spacer that mounts to your hub using your existing studs then supplies you additional studs in the spacer to mount your wheel. Have fun!

Okay, lets take this one step at a time! Worn springs and struts will make the car ride very bouncy and will make it ride a couple inches lower than it should. What you describe does sound more like someone played a trick on you or that your suspension suffered from some massive failure. But I have never heard of all four corners breaking at the same time. Regarding the noise you heard when driving, it could be because the tires are rubbing on the suspension or could be because the mustache bar broke causing the diff to be free at the rear. I had this happen once and it could cause the noise you describe and would explain whey the diff is hanging down lower. I suspect mine broke because of a loose bolt mounting the diff to the mustache bar which allowed the diff to rock up and down with enough force to eventually brake the bar. But the diff being located differently wouldn't/shouldn't have anything to do with the tire issue. The diff is held on by a front mount and the mustache bar so if it has moved one of these mounts is damaged. Next, the tire issue. Maybe your tires have been like this all along. Check the inside of your tires for groves from where they are rubbing, this will give you a good idea how long they have been this way. My tires are very close to the spring perch on the sturt on my car. Worn springs or struts would not change this relationship. Unless you have camber adjust brackets or the bolts are loose at the top of the strut tower I dont' see how else this could happen unless you attempted to jump the car. Are your lug nuts tight? Loose lugs could allow the wheel to shift when it rolls causing a cluncking noise and may change the angle of the wheel in relation to the strut. What size tires/wheels do you have? Tires too wide or wheels with the wrong offset can cause the tires to rub the suspension. Is your car lowered or do you have any other suspension mods? What part of the suspension are the tires rubbing on, the sprint perch of the strut? Jack up a corner of the car and have someone rock the wheel in and out from top to bottom, then from front to back while you look underneith to see what might be moving. That's all I can thing of for now! If you can answer these questions we can be a lot more helpful to you. I hope it turns out to be something simple!

Howdy, I have recently become interested in the different intake manifolds as well. From what I can tell the E46 manifold came on '71 series I & series II 240z's, I haven't check a '70 series I car yet but it may have one to. Which means it could be attached to either an E31 head or a E88 head. But the real key is the carbs that are attached to the respective manifold! The E46 manifold was used with the "4 screw" dome top SU carbs and the E88 manifold started with the later "3 screw" dome top SU carbs on the '72 or series III (as Carl Beck would say) 240Z. I do have an engine with each in my garage, as well as the legendary E36 manifold. From what I can tell visually the E46 and E88 look very similar the obvious difference is that the E88 is plummed for coolant to be delivered through the base of the carbs. This is also the second most obvious difference between the "4 screw" SU's and the "3 screw" SU's (the difference in the number of screws mounting the domes being #1.) Either should work on either carb setup. I think the main difference being the E88 with the "3 screw" SU's may warm up a little faster in colder temperatures. With the E46 and the "3 screw" SU's the water passages in the base of the carb will be wasted, while with the E88 manifold and "4 screw" SU's the manifold water passages will be blocked. I don't know if there would be a problem with leakage! I am leaving in the morning to take a long weekend away from the garage and the computer for the independence day holiday but will try to remember to take a closer look when I get back! Have fun!

So could I!! Have fun!

The speedometer gets a reading at the transmission, so changing the relationship of the transmission output rotations/wheel rotations causes the guage to read inaccurately. So any change to diff ratio or tire size may result in the speedometer to be incorrect. Yes the change will be by percentage but small tire size changes will not make much of a difference. If you go to http://www.geocities.com/z_design_studio/ and input your Z trans type, diff ratio and tire size you can use the resulting interactive graph to determine what your speed should be at a given RPM. Then compare to your actual results, of course this assumes your tachometer is correct! Have fun!

zedhead260, 2manyZs is right a 195/70 will have a narrower tread than a 195/50. 195 is not the tread width but is the widest point of the tire bulge when mounted on a particular rim size. If you look at a tire site they will tell you tread width, tire size, rim size used for measurement, overall diameter, etc. peterpit, I had 14x6 wheels on my Z and ran several combinations. I would say the 205/60 looked like the best fit on the wheel but if you are looking for better tire performance a 195/60 would probably fit better. I wouldn't go with 50 series on that rim unless you car is lowered because you will have a big gap between the tire and the wheel well. aapiss, If I remember correctly the stock wheel size in '72 was 5" and the tires where 175R14, I believe this was before they used aspect ratios on tire designation but I think it works out to be close to 75 series. Hope it makes sense and helps!

I know the V8 guys use the ZX tanks because they hold more gas! They can be made to work but I don't know how it is done. I bet there are novels on this at www.hybridz.org. If you don't find any info I can ask a local guy at the next Z onwers of No. Cal. meeting. He is building a '73 240z with V8 from IROC Camero and I know he is planning to use a ZX tank but he is not on line! Hope it helps!

wilby34, If the same force is needed to shift when the car is on or off it sounds like the problem is either with the shifter linkage or the part of the shifter that is internal to the tranmission. The clutch and syncros don't come in to play when the car isn't running. To be honest I cannot think of anything that could happen to the stock shifter that would cause a problem like that unless someone has replaced the plastic bushings with metal that was too tight a fit or has expanded or something. You said that your car has a short throw shifter. If the shifter has simply been cut than my previous comments apply. If it is like the more complicated short throw shifter in the MSA catalog than there is a better chance the problem is external to the trans. As a rule of thumb you always start with the simple cheap stuff first. I would take the console off and remove the shift boots and take a look at the shifter mechanism first hand. You may need to take it appart and clean it, lube it up, and reassemble. If that doesn't help check the clutch master cylinder for fluid and make sure the slave cylinder is operating smoothly. After, that you might need to pull the trans and open it up, something I have yet to do! Hope it helps! ***** dhayes5, You are kinda starting a different direction on this thread so I'll try to be brief, not a strong suit of mine. All the '72 - '83 4-spd & 5-spd transmissions (I don't know about the T-5) use the same type of shifter. I have 5, not including the one in my car, that I have accumulated over the years and they are all a little different. I have yet to figure out any pattern regarding which came from which year cars. Some appear very straight, some are curved and some are obviously modified but no two of the ones I have are the same! Have fun!