Weasel73240Z

So I took the head off of my 73 expecting to find a blown head gasket, or a crack in the head, which would explain the coolant in the head, and coming out of the exahust, when I got the car running a few weeks ago. And I found....nothing. The head gasket looked great, no blow-by that I could see. The cylinder head, at least what I could see (I haven't pulled the vales yet) looked great. No evidence of any cracks. The block looked great. However, I have the old wooden block holding my timing chain at TDC, so I can't see much of the piston walls. I straight edged the block and head, both seem very flat. I have to decide now whether to lose the timing chain block, and spin the motor so that I can inspect the block more thoroughly. I don't want to screw with the timing chain, so I was hoping not to remove the wooden block. I was really hoping to find a trashed head gasket to explain the coolant leakage, and finding nothing is really confusing. I had a lot of coolant in the head, and coming out of the exhaust. However, I didn't have any coolant in the oil pan when I drained it. Am I missing something? Should I just buy new gasket set, re-assemble, and hope that the head gasket was the problem? Anybody got any ideas?

I thought that I'd read somewhere that in many cases the Datsun's were undercoated at the dealership, and then touched up with body color around the rocker panels. Hence the overspray on the undercoating of an original paint job. But again, I've painted cars, and restored many others, and I think I can spot a re-paint as well as anyone. I'm 99.9% sure this is original paint based solely on the door and hatch jambs, inner fenderwells, engine compatment, rear hatch floor, etc. I'm convinced that the paint tag is just mis-labeled, this car was never red.

How common is this? The color code tag on my '73 says the code is 110, which I believe is red. However, the car is clearly 918 orange. I bought the car from the original owner, and she told me it was the original paint, from the dealer. Just by looking at the engine campartment and door/hatch jambs, its pretty clear the car was never red. There is even some orange overspray on the undercoating, which I understand is an indicator of original paint. Any idea whats up, is the color code tag just mis-labeled, and if so, did this happen a lot?

I'm thinking about changing the rear diff in my '73 240 from the stock 3.36, to a 3.90. I'm only gonna drive the car around town, not much highway driving, so I'm looking to add some "cheap" acceleration. Three questions: 1) is there a "best" 3.90 (a particular year or model) to look for, 2) is it a straight bolt-up, or are there any mods necessary and 3) will the same driveshafts and half-shafts work with the new rear differential? Thanks

I'm taking the motor out and apart to diagnose the problem with the motor (i.e. coolant in the exhaust). I took the motor and tranny out yesterday, and spent today powerwashing the engine compartment. The reason I'm pulling the motor apart is because it has just sat idle for too long. The head gasket and valve cover gasket were both dry-rotted. It may not end up a true rebuild, more like a tear down, clean, re-gasket, and put it back in. True, the car has only 26K, but most of those miles came 20 years ago, and it has basically sat since.

I've decided to rebuild the motor in my 73 240Z even though it has very low miles, and I'm just looking to build a nice, quick (but not a race car), mostly original, and (hopefully) very reliable 240. I'm gonna do the rebuild myself. I've rebuilt motors before, but this will be my first overhead cam motor. Previous experience was with American muscle cars. I bought a set of round tops on eBay, and put the original flat tops and the smog stuff in storage. I'm just looking for a slight bump in performance (nothing extreme like a cam), and it seems like 2.5" exhaust, electronic ignition and a good carb rebuild should get me there. I've only been on this site since I bought the car 2 weeks ago, but I think this question may open up some debate. Again thinking of reliability as the top priority and speed and HP as a somewhat distant second, what would you folks suggest as the best way to make modest performance gains, without sacrificing driveability or reliability? Just to set a budget, lets say I want to sink less than $1,000 into the engine.

Thanks alot for the pics, I found the fuse right away, right we're your pic showed it. I'm pulling my L24 motor and tranny this weekend, to figure out where the coolant leak was coming from. Hoping for just a bad head gasket, fingers crossed. I've decided to rebuild the motor even though it has very low miles, and I'm just looking to build a nice, quick (but not a race car), mostly original, and (hopefully) very reliable 240. I'm gonna do the rebuild myself. I've rebuilt motors before, but this will be my first overhead cam motor. Previous experience was with American muscle cars. I bought a set of round tops on eBay, and put the original flat tops and the smog stuff in storage. I'm just looking for a slight bump in performance (nothing extreme like a cam), and it seems like 2.5" exhaust, electronic ignition and a good carb rebuild should get me there. I've only been on this site since I bought the car 2 weeks ago, but I think this question may open up some debate. Again thinking of reliability as the top priority and speed and HP as a distant second, what would you folks suggest as the best way to make modest performance gains, without sacrificing driveability or reliability? Just to set a budget, lets say I want to sink less than $1,000 into the engine.

I have the pics you need, but I can't figure out how to post them here. Send me your email, and I'll send you the pics as attachments. I just pulled my 73 all apart and I have about 4 or 5 pics from all angles of the coil before it came apart.

I looked in the fuse panel, but I wasn't looking for an in-line fuse. I'll check when I get home. Thanx

I'm not getting 12V at the electric fuel pump of my 73 240Z. I'm trying to find the fuel pump wiring/relay under the dash. Anybody know where it is, what it looks like, etc.?

So I got my 73 240 to start and idle pretty well last night. It seems that the gunked up Hitachi flat-top carbs were the problem, that's the good news. The bad news is, when it was running, I was getting coolant through the exhaust system. Not a little sweet smell like I've seen before, but actual (unburned, clean) coolant. I assume the head gasket is gone, and the coolant is getting directly into the exhuast manifold. If it were going into the pistons, I don't think the car would run as well as it does, and the coolant coming out of the exhaust wouldn't be so clean. Is there anything else that I could be missing to explain coolant (a lot of coolant) in the exhaust system, before I pull my engine, and rebuild it?

Since I'm going to get the car running with the flats on, I guess there is always a chance I could keep them. If the car runs well with them, I suppose I wouldn't necessarily change them. If I do decide to keep the flats, will removing all the smog stuff affect them much?

Thanks to everybody for the input. I think what I'll do is get the car running with the flats on it. The lady I bought it from said it ran fine when it was parked, so I plan to get the motor running before changing anything. Then I think I'll probably store the flats, and install a set of earlier rounds. I'll store everything from the flat tops (and the smog stuff), but in the end, I want to drive this car, not show it. I want the most reliable carbs I can use, and I want the car to perform the way a 240Z should. And it seems to be the concensus that rounds tops are the best way to get there.

I hear a lot of differing views on this board about whether to keep the Hitachis or trash them for older SU's. The car only has about 26,000 miles on it, and other than desmogging, I want to keep it original.

I've got a 73 240Z with the original Hitachi flat tops, and very low miles. I'm going to remove the smog control stuff, since I don't need it in Massachusetts anymore. The car has sat for a long time, and hasn't run in a year or so. I took apart the carbs and found a stuck float needle. I haven't started the car yet, I'm waiting until I have cleaned all of the fuel lines and the fuel filters are all replaced, but I'm sure that was the problem. A friend who has worked on older Z's before suggests I get the car running properly with the smog stuff on, then remove it and adjust. It is my understanding that these carbs work much better without the smog stuff, so why not get the carbs running and tuned with the stuff gone already? What parts of the smog equipment (i.e. shared vaccuum lines, etc.) directly affect carb function? Any advice and/or tips would be appreciated.

Sorry for the confusion, they're Hitchi flat-tops. I'll pick up some 20WT fork oil and new fuel filters today, and try starting tonight. I'm pretty sure the stuck needle valve in the front carb was the problem. I have another question. When I was working on the carbs, I noticed that one of the coolant lines (the one that exits the rear carb and appears to recirculate coolant back to the block) was pinched right near the firewall. It looks like it was done intentionally, not like it was some sort of damage. The pinch is perfectly done, almost like sombody squeezed it in a vise. But I can't seen how the coolant recirculates to the block, what's the deal? If my description doesn't help, I'll take a picture and post it. Thanks.

Thanks to everyone for the help. I took the round tops apart today (I just couldn't wait any longer) and I think i found my problem. The needle valve on the front carb was stuck, so the fuel bowl couldn't fill. The bowl was dry as a bone. Cleaned it up, freed it up, and I think I'm in business. I was amazed at how simple the design was once I got the carb apart. I totally cleaned the damping piston housings, and got them to slide real easy. I haven't started the car yet, because I don't have any damping oil, and I spilled what was in there all over myself when I took it apart (lesson learned). I'll get some tomorrow and see if I found the problem, fingers crossed! How much of the damping oil should I put in to start? They are pretty much dry now. Just to be safe, I'm replacing all of the fuel filters, cleaning all of the lines, and I tested both the mechanical and electric fuel pumps. They both seem to be working fine. I've got a feeling that I'll have her running by tomorrow night. I'm think about removing the emmisssions stuff, but the car is so original, I'm afraid to remove anything. What do you think, to desmog, or not to desmog, that is the question. I'll post some pictures of the car once I get a chance. It really is hard to believe that this car has been in Massachusetts for 34 years!

I just bought a 1973 240Z with 26,000 original miles on it, from the original owner. The car is in amazing shape, very little rust, but has not run much over the last several years. The girl I bought it from said she started it every few months, but it hadn't started for about 8 - 9 months. Its been garaged in Massachusetts since it was new. I'm new to the Z (I've wanted one my whole life, and finallly found "the one"), and I definitely don't know much about these Hitachis flat top carbs. The car will run if I spray starter fluid in the carbs. I'm getting fuel to the carbs (I cranked it with both lines disconnected), and it runs with starter fluid, so I'm sure there's spark. What should I do first, just a real thorough carb cleaning to make sure there's no build-up inside. And if that's the answer, does anyone know where I can get an exploded view of this type of carb. I don't like working on carbs "blind". Nothing worse than seeing a spring fall out, and not knowing where it came from.