zeiss150

the clunk from the diff could also be from the mounting plate "above" the differential. I use to have that clunking problem then I replaced that and no more clunking. Its a steel plate with rubber on it, over the years the rubber goes away and you are left with a "free floating" differential. If you want to check your diff, jack up the back end a little and spin the tires that will tell you if its your U joints or the differential mounting bracket or if it is the differential. Differential fluid always smells like hell BTW. I hope this helps. If your gonna go through the trouble of putting in a new diff why not put in a 3.90? Just wondering. if you are worried about the speedo being correct just have them send you the speedo cog from the Z they pull the diff from and you'll be set. or just buy a "white" 19 thooth cog from nissan and you will be set too.

How do you know it's been bored out to 3 liters? Thats not easy thing to do. The block usually needs to be sonicly tested to make sure the walls are thick enough to bore that much over. I believe its a a 120 thousands over bore, and if thats the case the best BLOCK is the N42 block. All of the stock 280z blocks were N42's. that much of an over bore makes a 2949 cc engine (i.e. 3 liters) block codes... 240z = E31 and P30 260 = P30 280 = N42 280zx = F54 If it is a 3 liter it should be fun to drive... once you get it fixed. The block code is located on the drivers side to the right of the engine mount

suposedly the 260z's intake is the best of the carb'd intakes (n36 I believe) The round tops just bold right up to them. There is a guy on this site that is working on a RWHP test on the differance between the E88 intake and the N36 intake to see if there is really a differance. I don't know how far he's come with his test.

a 3:90 cog in a 3:54 rear end WILLl through off the speedo that much. I had a 390 in m 354 and it made it seem like i was going almost 90 on the freeway I was probably really only going 67 mph or so cause cars were passing me like crazy that's how I new something was wrong. Does anyone know if they will ever do an "Overhaul'n" T.V. show on a Z? I submitted a request to have one done but that doesn't mean $hit. Just wondering.

The speedo needs a "black" speedo pinion gear, known at your nissan dealer as a 17 tooth. If you try to order a black one they will just stare at you. The differential is what controlls the acuracy of your speedo so it doesn't matter what trans or engine or speedo you have in the car. I think the stock differential is a 3:54 which needs a black 17 tooth gear, the blue is for a 3:70 18 tooth, and the white is for a 3:90, a 19 tooth. If you had a white gear in there that means that your trans was from a 81-83 280zx NON turbo that had a 3:90 rear differential. I hope this helps good luck!

ummmm im just guessing so I could be totally wrong but here go's ... check the throttle body and make sure its not hung up on anything, check your AFM make sure that the flap doesn't have anything stuck keeping it open, check any leakes in the rubber leading to the AFM, look for any vacuum leaks, check the throttle linkage from the peddle to the TB see if its stuck anywhere, this one is a long shot but make sure the timming wasn't messed with. thats all I can think of Good luck!

Hey Bruce Thanks for the reply and advice. The banjo filters were taken out when I rebuilt the carbs 3 years ago. I'll try to turn up the needels .5 turns and see if that gets rid of the rich idle condition. I think the problem with most of us weekend mechanics is that with the 35 year old, non computer technoligy, carborators we have a hard time getting the perfect AFR (which is what we are all hopping for). With three hundred plus needles to chose from it becomes sort of an overwhelming task to pick the right one for the custom engine that a persone has just built. I have read hundreds of SU posts in the 3 years I've had my Z and most of the time I just end of with more questions. For such a silmple carborator it sure has a lot of tunning potential. I think I remember reading a post from you Bruce, about a college student that was doing a bunch of tests on the SU's for different needle profile combinations with different engine applications (i.e. cams, displacment,heads) and his school was getting in the way of our SU tests, how's that comming? It would be a wonderful list to have ... sort of like the Lengine calculator ... put in your displacement, head, cam, valves, exaust system, timing, and anything elese that might have an effect and the program would tell you which needle, nozzle, and how many turns. Dare to dream! Matt-

the other option is (instead of carbs or stock FI) to use a stand alone ECU for your FI system(haltech or megasquirt). The stock Z and ZX FI ECU suck. If you get a stand alone model you don't need to tie into much of the 240 wireing harnes. You just need to get an engine temp sensor, map sensor, wide band O2 sensor, I think you can get an EGT sensor too, tie into the RPM loop on the dizzy,custom fuel rail and larger injectors, new fuel lines and a better fuel pump, and a 60mm throttle body. If you put that stuff on, none of it (as far as I know)will effect the 240 harness. now if you wanna go through all that trouble go ahead.... OR.... you could just put the SU's back on and get the same performance as the custome FI system or maybe even a little better. If you have the round top SU's Thats the way to go. The only reason I can see to use FI is if you live in a cold climate and you dont want to have a hard time starting your car in the winter OR you are going to go turbo. Good luck and let us know what you do!

Ok so I check everything and here's what it turned out to be... I was running to lean:stupid: My floats were just fine I had plenty of fuel in the bowls I think the real problem is the needles im using. I had it running perfect for idle and normal driving conditions. But once I punched it the carbs would just run out of fuel under heavy load. I think the only way to really get the SU's "running Perfectly" is to have custom needle profiles made for specific applications. I'm using SM needles with stock 72, 3 screw carb, nozzles. I believe that the SM needles run rich at idel but under heavy load work great. I tried the stock 54 needles but it ran worse with those. With the SM needles I get about 21 mpg so I'm not running that rich but the exaust smell is real annoying at idlel. Right now I'm about 2.75 turns down and it idles great but is a little "smelly" Has anyone ever done some custome needle profiling and if so what did you do? Now when I punch it I get up to 45 mph in 1st gear at 6500 rmp and it does that in about 3 seconds with no loss of power. Thanks for your help guys!

The P90 is an excellent head. It has square exaust ports. Its basicaly the same head as the N42 but the P90 has closed chambers which is better for controlling detonation. On a flat top piston short block you get a CR of 8.5:1 which is not bad for a N/A engine and if you want to go turbo, its almost perfect. If you never want to go turbo, then mill the head 80thou and buy some cam tower shims along with the 80 thousands longer valves put a bitch'n cam in there, and you have a bad arse, detonation free N/A 10:1 CR motor. The P90 (and the P79) were the best of the Nissan L28 heads in some peoples opionions (don't even get started with the maxima N42 head, I'm talking about Z engines). As far as the internally oiled cam... so what... my N42 has an internally oild cam, it works great. With all of that said ... I have a fun as hell, F54 flat top block with an N42 head with a stage 1 cam and SU carbs my engine has 9.2:1 CR because I have a 2mm head gasket without the 2mm head gasket it would be almost 10:1. The only reason I would change my set up is because I'm gonna go turbo... and if your gonna go turbo you need a better head (the P90 or P79) in order to controll detonation. My advice to you is to do a bunch of research (which you seem to be doing) think about how much rear wheel horse power you want and whether or not you would ever think about turbo. anything over 190 RWHP would require major head work and serious intake and carboration work. With turbo 225 RWHP can be reached with simple modifacations. and the potential for 300+ RWHP can be obtained for what you would spend on the Head work for a N/A 225 RWHP head. I'm not trying to convince you of anything ... I just wish someone had layed down this info before I built my Z ... Cause I would have gone turbo for sure... now I have to do it again. Good luck and let us know what you do. P.S. Check out this awesome page http://www.geocities.com/zgarage2001/p90.html

Some people on this site are teachers. The type of person that enjoys sharing info will spend the time to answer a thread in detail in the hopes that it will inspire a new Z owner to learn how to work on, and enjoy their new hobbie. The other type of poster to this site is a person that just wants to tell the new Z owner that they should have searched before asking the question, or they will just say, spend some money and get it fixed. the great thing about the internet is that for both types of people the "teacher", and the "teller" they each have a "student" , "listener". I prefer the teacher, student combo, thanks for being a good teacher Will! :burnout:

sooooooooo.... What happened? More HP? Or is it just lame BS?

Thanks for the reply carl, The damper oil is a good tip but I have fresh oil in there, 20wt (bought it from MSA just for SU's) so I don't that thats it. I tried the hard acceleration with the vacume advance pluged in and "unpluged" and there was no differance. As far as my static timing go's I have it at 17 BTDC I think that translates to 35 degrees total timing. I'm also using a 82 ZX dizzy (freshly rebuilt). Let me tell you why I think It might be the float bowl ... My engine is an L28 20thou over with an N42 head with a schnider cam and valve train (460 270, a mild cam but I wanted to bleed off some of the CR) My SU's are rebuilt and are running SM needles with stock 72 nozzels. So my engine with WOT can suck some gas. I was thinking that when I punch the gass that hard and that fast, it just drains the bowls out and I looses all power, it actually "sputters" like its out of gas. With the slower acceleration up to 6k (much higher and I can feel the same loss of power but no sputtering) it alowes enough time for the bowl to fill up just enough to power the engine. I sort of remember reading a thread about this problem happening ... the answer was to put a non FI fuel pump in the system to keep the bowles full 3-5 PSI I believe. So did I change your mind Carl or am I missing something. Matt-

A bump for my thread!

Hey guys, I did something I've never done before today and I noticed something weird. I decided to drive my Z bare foot and I noticed that when I put the peddle to the floor my Z sort of sputtered and lost power at about 5k but if I pushed the peddle slower and not quite "to the floor" it would give me power up to 6.5k. I think with my bare feet I could get a better feel for where the peddle was at. I know that the nozzles are turned down enough to feed the engine (I tried to richen up the nozzles and that didn't help the problem). Since the problem seems to come on at "instant WOT" and not with a gradual WOT I guessing that it is a problem of not enough fuel pressure to keep the float bowls filled. I don't have an electric fuel pump (I know ... a non FI pump 3-5 psi) I've just been using the mechanical pump. So what do you guys thing? Dry float bowles? I await your wisdom!

I would go with the 8.5 inch I'm pretty sure that = 225mm and if it doesn't ... still go with the 8.5. Rock on Z people!

All the clutch kits are universal EXCEPT the turbo and 2+2 models they have a larger serface area 240mm vs. 225mm I think. I'v never heard of "8/12 or 9/12". But I don't know everything (as if I needed to state that:stupid: ) I hope you have a buddy that can help you with this job, I did it by myself and I set a new record for cuss words utterred in an afternoon, seroiusly, check Guinnes. Good luck and let us know if we can help. Matt-

I believe that kind of an "explosion" out of the exaust is a sign that the timing is "off" The engine is firing the intake charge while the exaust valves are open. The explosion is suposed to happen with both valves closed. Check your timing is most likely off. If I remember correctly (and thats a big if) you need to advance your timming a little. Just a shot in the dark. I hope it helps. Matt-

anyone ever heard of a product called "freez12" It is suposedly a replacement for R-12. I had my Jeep A/C recharged with that stuff and it was about $15 a pound. I think you need to still have some R12 left in your system but unless you have a huge leak there should be some still in there. My Jeep A/C was so low that the compressor shut off and my local A/C guy filled it up with what he called "freez12" and buuuuuuuuuuurrrrrrrrrrrr, nice and cold. Just a some Info I thought I would pass on. Rock on Z people! I found it on Ebay Freeze12 check it out http://cgi.ebay.com/ebaymotors/FREEZE-12-FREON-R12-SUBSTITUTE-FREEZE12-3-CANS_W0QQcmdZViewItemQQcategoryZ33543QQihZ017QQitemZ270002839621QQrdZ1QQsspagenameZWDVW

Thanks Will ... Now I can pollish it to a mirror finnish.

What is the window frame made out of? I thought it was stainless steel but a magnet sticks to it? Are they steel that has been chromed? or are they a low quality stainless? I just wanna know so I can ether get them rechromed or just pollish them. Thanks.

How's your timing? Also How's your compression? If you have low compression no matter how much fuel and spark you have it wont run. Are you using the L20 FI computer? It might be delivering the fuel at the wrong time if your fuel is injected on the exaust stroke ... well, no vrooooooom. If you are sure you have spark on the compression stroke then I would look to timing and I would take a close look at that computer and make sure it is fireing on the compression stroke. Don't forget to check your compression on all 6 cylinders it should be somewhere in the 150 - 175 psi range ... If its below 100 you have a major problem. Just some ideas, good luck :burnout:

pull off the wheel and give the drum a few good wacks with a rubber mallet. If that doesn't break the rust free then try moving the break shoes through the access whole. good luck!

Just a thought... Does that year have a throttle positioning switch? If so check to make sure that is still working right. This could be a horrible suggestion but ... what the hell, right? good luck, Matt-

I have the dizzy and coil from an 81ZX on my 72 240 it bolts right on just take the dizzy collar from the zx eninge, and i'm still using the ballist resistor. I was told that the tack ran through the resistor and that if you didnt use it it wouldn't work. bad info I guess. P.S. I had to rebuild the dizzy, but once you put it on its a great upgrade, oh and don't forget the 70 amp altinator upgrade from the zx turbo engine, its a must!