240ZMan

One other aspect you can use to tune the handling is tire pressure. I have 14 x 7 rims with Goodyear 215/60-14 Eagles all aorund (not my choice, the PO had just put them on before me). They are a very hard tire with OK, but not great grip. I too found more understeer than I liked, so I have the fronts set at 35 psi and the rears at 30. Didn't make a radical difference, but it improved the crispness of the initial turn-in, and did make the car more neutral in higher speed sweepers. This is not my daily driver, so it only goes out on dry clear roads. I'd be careful about this much of difference between front and rear if you drive in the wet. Until I can put the rear sway bar and bigger front on, this was a good (and FREE) improvment.

I tried 2manyZs suggestion tonight and blocked off the water intake to the back of the manifold. It did help a bit, but not all the way. But I think I figured out the real issue: my throttle bushings on the rear carb are leaking like a sponge. I had tested them earlier after rebuilding them by spraying carb cleaner, and the front had slowed the idle a little, but it wasn't too bad. The rear had been fine. But I had done this with the hood up and not much latent heat in the engine compartment. Tonight I let it idle in the garage with the hood closed for 10 minutes and then sprayed carb cleaner. The rear almost killed the engine! I put some grease on the ends of the shafts for tonight, but I suspect I'll be calling ZTherapy tomorrow. $$$ Ouch.

So if I understand your thinking on this, if the thermostat isn't cutting off at 80 degrees, I may be getting too much heat in the manifold/carbs and seeing some of the symptoms of vapor lock? I'll try plugging it this weekend. I'm not too worried about losing the heat in the manifold during warm up as drivability has been excellent, even within the first minute or two when it's 30 outside. Thanks, Daniel

I've never heard of lead grease. What would it do for the gears? Interestingly, the clunk only comes when I change the load on the rear end, such as starting up or reversing. But if I drive along in 2nd gear and alternately step on the gas and then lift off, often there won't be a clunk. Not what I would expect if there was too much play inside between the pinion and ring gears.

The intake manifold has an "N33" cast on it and I believe is stock. The water lines are hooked up but I can't find the valve you mentioned. The water line at the rear of the manifold goes through a rubber hose then to a metal assembly. The other end goes behind the engine around to the passenger side and connects to the coolant hose there. If there is a valve in it it must be inside the block of metal in the middle as I can't see any signs of anything that moves from the outside. Also, the fitting off the bottom of the assembly was cut and crimped/welded (poor man's cap?). I can take a picture and post if that would help.

I've got the dreaded "clunk" in the rear end of my 73 240 when starting up and shifting, and reversing. Not always, but some of the time. From this forum I assumed my mustache bar bushings were shot. But I got under there last weekend and they look good. In fact I couldn't budge the front of the diffy at all with my hands. I even brought the floor jack over and applied a little lifting on the front and it didn't move. I tried moving the different u and half shaft joints with my hands and nothing has much play in it, at least for a 30 year old 200k mile car :classic: I'm wondering now if the problem is inside the diffy? And given that the PO says that's the way it has been as long as he can remember, should I even worry about it?

tanny, On my 73 with stock fuel rail, the return line on the rail is smaller, but at the end of that nipple where the rubber fuel line connects there is a further restriction. It's almost as if the nipple had been fully closed and then a small hole had been drilled. It's been a while since I looked at it, but I'd guess it was smaller than 1/16". Daniel

alien-e, I had the same issue as you. In my case the problem was that the needles were not set the same amount into the pistons, even though to my eye they looked identical. Someone here suggested the following which worked for me: - remove the pistons from both carbs - set the needle into the piston on one of them so that a metal straight edge just touchs the shoulder of the needle. Note that the shoulder is NOT flush with the machined groove. Tighten that set screw. - leaving the set screw on the other piston loose, gently point the two needles at each other and bring the pistons towards each other so that the needles are next to each other and touch the base of the other piston. (Sorry I'm not explaining this very well, but if you hold one piston in each hand I think you'll get the idea.) - when the needles touch the base of the other piston, you will know that they both stick out exactly the same amount. - tighten the other set screw and reassemble. Hope this helps.

I had heard that in CA when an engine is swapped in that is NEWER than the body, the engine year (not body year) becomes what the smog is measured against. I don't live in California anymore, but I'd check that out before getting too far down the road on your plans. BTW, hope I'm wrong! Daniel

I have a strange problem with my 73 240z that has got me stumped. My setup is as follows: - Original 240 bottom end - E31 head - stock - 72 3 screw SU carbs - early 70's aircleaner - Pertronix electronic ignition with coil - stock exhaust - all smog removed, except EGR which I've put a gasket under to make sure it stays closed Whenever the engine compartment gets hot, the idle begins to slow down and the engine stumbles. This will happen almost everytime I park and let the car sit (engine off) with the hood closed for about 5 or more minutes. Even now when the highs for the day are only about 50. Yet a few weeks ago when we had highs in the 30's the problem never showed up. Sometimes just letting the car sit idling will build up enough heat to slow the idle down. Pulling the choke back a bit will bring the idle back up, but not as smooth. Giving a little throttle will do the same thing. Driving around for a few moments on a cool day makes the problem go away. I put a fuel pressure gauge in and the pressure stays between 2.5 and 4 psi always. I don't see any difference when the problem occurs. One thing I can't tell yet is why the idle is slowing. By that I mean that I suspect the mixture is going rich because I can tell the smoothness of the idle is not right. Yet when the engine compartment is not hot, say when the hood is open for a few moments, the idle is perfect, nice and steady and smooth so I think the tuneup is ok. I've checked the timing and dwell while the problem is present and both are spot on. I've rebuild both carbs completely following the ZTherapy tape. Both have new needle/seats in the float chambers. One thing that I can't tell if it is normal or not is that sometimes when I open the fuel cap there will be a small amount of pressure escaping. I would have expected the tank to build a small vacuum, so this has me wondering if it's part of the problem. But when I open the cap it makes no difference on the idling. I tried taking the hose off the 3 way purge valve and can blow back into it. Leaving it off doesn't make a difference so I figure the valve is ok. At this point I am out of ideas. I still believe that the problem is with something in the engine compartment that changes the fuel delivery when too hot. Any ideas? Thanks, Daniel

I'd be interested in seeing a picture or two of the connections at the alternator. I agree with you that I'd like all my load + alternator on one side of the ammeter and the battery alone on the other. I don't like to "get used to" a gauge that reads somewhere other than where it should, especially since it will depend on what accesorries I am running at the moment. Of course, that's just me.:classic: On the other topic of whether to switch on the positive or negative side of the load, I can't see any reason why it would make a difference either way on the load and hence life of the contacts. However I can see pros/cons on issues of safety vs. cost of building the car. I'll bet that those issues dominate the decisions of the automotive engineers who make these decisions. My .02. (Fun topic!)

Thanks Daniel, I share your view of how the system works. My question if others had some experience with this configuration (connected straight to the battery) was just trying to be sure that "theory" and "practice" would be in synch:classic: BTW, I put the relay on the positive side. I actually took the power to enable the relay off of the light switch under the steering wheel through another under-dash switch so that I don't have to remember to turn off the driving lights separately.

Another point of view on reparing the switch: go real easy on what you use to clean the contacts. Usually the metal has a thin layer plated on the outside to improve the conductivity and reduce the rate of oxidation. Any agressive use of sandpaper will take that off. You will solve the problem in the short term, but it probably won't last as long as it could. The best thing to start with is the eraser on a pencil. Don't use one of the modern white plastic ones, you want the older style red type. Other nice feature is that it's easy to get it into tight spots. Of course, if that doesn't get the job done, then go to more agressive things such as sandpaper. At that point what do you have to lose?

73 240Z: I just got the driving lights working for the first time. They are powered directly from the battery (separate in-line fuse) and activited by a relay. I noticed that when they are on, the ammeter shows a constant state of charging that returns to neutral as soon as I turn them off. This makes sense as the ammeter doesn't know the difference between current charging the battery and current flowing into the lights. So my question is two fold: - anyone run like this for a long period to have some experience that this won't bother the proper charging of the battery? - if I decide to rewire from the battery to some other point "before the ammeter", where should that be? I'm thinking that the big red main power feed into the fuse box would be good, and I'd move the inline fuse close to it. But is there a better place?

I live in Colorado at about 6500 feet elevation. I've got a 73 with 3 screw round top SUs. As I never go lower than Denver (~5000 feet) my tuning is optimized for altitude. But when I had the car in the Bay area where I used to live, it certainly had more power. At this altitude the general concensus is that an engine makes about 20 - 25% less power - that's both torque and HP. At first it's frustrating, but eventually you get used to it

I too have a 73 with both electric and mechanical pumps. My electric makes a very loud (at idle) ticking noise. Since I also have the mechanical, I put a switch in and leave the electric off all the time now. Haven't needed to turn it on yet. Oh, and to Inf's comment about the mechanical pump ticking after shutting down the engine when warm, mine does that as well. It's most noticeable for me when the day is warm, or hot even. Now that the weather has cooled (I'm in Colorado) I don't notice it much. I've opened the pump up looking for some problem, but it's clean as can be and I can't see anything that would cause it. I figure I'll wait until the spring and warm temperature to deal with it.

Perhaps I can add a bit more: the fuse clip on the hot side is not physically has tight as it is on other fuses. I had thought I might be able to tighten up the rivet by tapping it, and it helped some, but after a few months it seems to be getting worse again. I'm thinking of soldering it, but I hate the thought of possibly melting the plastic around it so I was hoping someone would have some other ideas. I saw another thread that suggested cleaning the multifunction switch to reduce the load, but I didn't understand how dirty connectors would increase the current draw. It usually works just the opposite.

On my 73 240, I'm getting ready to replace the front brake pads, and possibly rear shoes. The brakes are stock and I don't have any plans to upgrade for a while. On my previous vehicles (BMW 533, 325, Volvo V70 T5) I found that replacing the pads with Metal Master semi-metallics gave me better fade resistance. My car is mostly driven on the street (and somewhat hard at that), although next season I plan to attend a few autocrosses and a track day or two. So have any of you tried the Metal Masters? I've also heard of a brand, name begins with an "F" I think, that was raved about for track use. But given I will drive very little on the track, don't know if that makes sense. Also, this is not my daily driver, so I'm really not too worried about the life of the pads - within reason of course :classic: Thanks, Daniel

1. I believe that fuse is for the rear taillights. 2. I haven't added any extra electrical (yet) 3. It only get's hot when I have the lights on which I guess is because that's the only time the tailights (not brake lights) are in use. What do you think?

And it's the left side of the fuse. Wow, that's amazing, how did you know!

I have a 73 340Z with a "new" fuse box. The previous owner had it replaced, but unfortunately one of the connections gets hot enough to burn a finger. I tried taking the box out and tapping the rivet/crimp with a 3/8" socket extension underneath and a drift on top, and it helped some, but it's still too hot for me to feel good about it. How have others dealt with this kind of problem? The box is othewise in great shape (it should be - it looks brand new and from the receipts, it looks like he paid ~$200 - ouch!) Thanks, Daniel

Having recently gone through the same issues, I'll add one more thing to watch for. For my car (73 240 w/E31 head, 72 carbs, all else stock) after reassembling everything I had ablsolutely no power after 5k rpm - like a rev limiter had kicked in. Turns out that the notch on the cam was just to the right of the oblong mark just as the book says it should be. I also had made sure that the two "silver" links were correct when I had reassembled the engine. Eventually I tried retarding the cam by moving it one link back, and low and behold all was well again. Not sure if you will have the same issues I did, but watch for it. And best of luck!

<b>SOLVED!</b> This morning's clue that advancing the cam timing resulted in the max revs occuring sooner made me wonder about the overall cam timing. So I tried a few combinations of retarding the cam gear and found out that the best case occured when I had the cam gear on the #1 setting, but moved the chain one link to the right (retarded). This resulted in the notch ("V") on the cam gear being centered on the oblong mark. Before the notch was to the right as Nissan shows in the book. Now it pulls to past 6k rpm, albeit there's a fair amount of vibration above 5k. Also, the idle is more stable now. I've gone through the carb tune-up steps again and what an overall difference in the engine! So in the end it was all about the cam being too far advanced. What's so frustrating about this is that book shows the original setting I had (notch to the right of the oblong mark) as being desired, but clearly that's not the case. Many thanks to everyone who made suggestions. The good news is that in the process of getting this resolved I think I've gone over just about everything else possible, and overall this is probably the best the engine has run in a long time! Now on to the clunk in the rear, the pulling brakes, etc.... :classic:

Thought I'd share the latest. I only had a little time this morning so I moved the cam gear to the #2 position. The Nissan book says this results in 4 degrees of cam advance. I had expected to feel the power peak move up the rpm scale. But interestingly the point of maximum revs moved down from about 4800 rpm to 4500 rpm. And just to clarify, when the engine hits the max rev point, it just stops increasing in revs - period. If you're not ready for it, you almost fall forwards as the decrease in acceleration is that sudden. I think I can rule out valve float now, and my instincts point towards air intake, not fuel. I'm going to look at the little bit of smog control that's still on the engine. I'm wondering if at the max rev point if something is opening up enough that the engine is going too lean to rev any higher? Just a thought.

Kyle, Good catch on the fuel filter. Actually it was the first thing I changed, but I forgot to list it. I was going to try your suggestion on bypassing the electric fuel pump, but then decided not to with the following reasoning: at WOT it stops reving at just before 5k. I can hold it there for some time, and even tried it up a long grade. As soon as I let up a little it revs higher. I figured if there was a fuel delivery issue upsteam of the carbs then this should have drained the floats enough to cause a miss of some sort. But it didn't. Also, power right up to just before 5k is actually pretty good. It just stops reving any higher, literally as if there was a rev limiter. Plus, in the past I have been able to rev this head and motor to 6k, although it wasn't strong above 5k. So I don't think it's floating valves. Also, removing the aircleaner backing plate shouldn't make a difference if it was the valves floating I think. I've found there are 2 schools on float settings: one who feels they need to be set extremely accurately, and the other who never even deals with them. My own experience so far lines up with yours. I'll see about getting some fittings to hook up a vacuum gauge into the cockpit to see what's happening. I think that might give me some clues. I'm a little less comfortable with the gas can idea so won't try that one right away. Thanks for the suggestions!