Guest bastaad525 Posted July 8, 2002 Share Posted July 8, 2002 Okay here's the deal, I had an '80 280ZX N/A, which I had put a lot of work and money into fixing up. Rebuilt the motor, kind of mild I guess, with an N42 head with mild porting, stock cam, stock size stainless steel tuliped valves, stock block bored .060 over with flattops. Intake and exhaust all upgraded to performance parts (mostly from motorsport auto). Other drivetrain mods too... suspension mods, you name it. I finally happened upon a '72 240z in great shape (body wise) for a very good price, and have now transfered the entire drivetrain over to it. Unfortunately the mechanic that did the work did not think he was up to the task of transferring the FI system over, so I ended up having to go with the SU's, after rebuilding them with the Ztherapy kit. The mechanic tuned the carbs (he's been doing these for 15 years) but no matter what he does, or what I do for that matter, this relatively fresh motor is now running like crap. I figure even with the Ztherapy kit these carbs are old and worn and probably need at least the bodies/throttle shafts to be replaced. So what I'm getting at is.... that age old question. I'm now faced with a very hard decision (for me anyways). I still have the ZX here with the FI stuff still in it. Would it be worth the extra cost in labor to transfer this stuff onto the engine? I can say that when it was in the ZX this motor ran BEAUTIFULLY. However I know there are guys out there who can work magic with SU's. It would cost quite a bit less just to get new bodies and fully rebuild the carbs. In the end, it really is coming down to which is the better solution? Which will produce the most power and best reliability and driveability? I need advice! Quote Link to comment Share on other sites More sharing options...
Guest jurven240z Posted July 8, 2002 Share Posted July 8, 2002 I would say are you the machinic type of guy. My SUs have just new needles and valve in the float chambers and yes they don't balance evenly but run great on the L28E. Went with machanical fuel pump. Now I too have the FI system sitting in my shed but do not like all the electrical wiring. The only thing is the knocking at shut off think it is the old timing chain. Engine worn but can fill the difference between the L24 and L28E. You might want to give the sythoms that the engine/SUs are giving you for some feed back on the problem. Did you change needles? Timing set at? Machanical/eletrical fuel pump? Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted July 8, 2002 Share Posted July 8, 2002 Heheh I didn't post the problems I'm having because I didn't want them to have bearing on the decision... even if the carbs were running perfectly I'm still trying to decide which between the two is the BETTER choice overall. I say this, because if it ends up the carbs are better I could spend less money or maybe pretty close to the same amount even and get fully rebuilt carbs, as what it will most likely cost to get the FI put in there. As far as the carbs I have now, they had a 'soft rebuild' using the Ztherapy kit, which is new needles (SM needles), nozzles, grose jets, some gaskets, fuel tubing from float to nozzle (soft silicone type) and some other little stuff. The problems I'm having right now are hard starting, rough uneven and unstable idle, car dies all the time for no apparent reason, dieselling after shut-off (sometimes really badly), backfiring thru both exhaust and intake, bad hesitation on acceleration, and an apparent innability to get the fuel mixtures tuned right. I've gone thru and adjusted my timing with a light gun, cleaned and regapped plugs, adjusted the valves hot to spec, elimated any and all vacuum leaks or POSSIBLE vacuum leaks... the list goes on and on. Even after following four DIFFERENT prescribed methods of tuning, from books and the internet, the damn things still dont' run right. I'm still open to the idea of sticking with SU's but I dont' want to plunk down $600 for 'new' ones to find out they're still not gonna work right or well. On the other hand the FI system I have in the ZX still ran perfectly in that car (and the engine itself before I put the SU's on it) so at least they are a known commodity. As far as I know the carbs I have now are complete junk, but by and large everyone who has SU's in their Z thinks they are great... I just need to know which is better. If I'm gonna spend the money either way... best to make a well informed decision. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted July 8, 2002 Share Posted July 8, 2002 I am in the process of fitting some SU's on a 260 I bought. I piddled around with them and had some problems initially, but then got them to behave. I ordered the video and some needles from Ztherapy and watched the video, and man did I learn a lot. If you think you have worn shafts, just get two replacement bodies from Ztherapy with the roller shafts for 175.00 for the pair, and get the video and transfer your stuff over. Balance the carbs like in the video, and go. It took me a good hour to get the two carbs balanced in the "drop test". I may have to get replacement bodies, but once I get my header situation straightened out, I will let you know how the car runs. FI will spoil you. I wondered why I went to all the trouble to come up with SU's when I could have just fuel injected it. I think in the end, I will get more performance from the SU's, but it will come with a price tag, namely not the easy starting I have grown accustomed to. Putting fuel injection on your car should not be that difficult. The biggest problem is going to be with the return line to the tank on the 240. It is to small to handle and electric pump other than the stock one. Good luck. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted July 8, 2002 Share Posted July 8, 2002 If I end up going with the FI I'll most likely keep the stock 280ZX fuel pump, as it was working fine and that will be another part I dont' have to spend money on! I'm pretty sure if I got the new bodies from Ztherapy the carbs would run okay, I mean... how many thousands of people out there run SU's? I am spoiled by FI... using a choke sucks!!! I guess really though I'm probably after reliability and driveability more than power or anything else. That's why it's a hard decision to make for me... I've always heard that SU's are so reliable, yet here I'm having so many problems. On the other hand I had heard so many times how early ZX FI systems were buggy as hell, yet mine ran great for 5 years. CONFUSING!!! I've been thru the Ztherapy video so many times it's all already filed away in my brain... I feel like I"m a pro and should be able to set up any SU's perfectly... but not mine! Thanks for the tips man. Now lets have some more opinions! Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted July 8, 2002 Share Posted July 8, 2002 If your asking for opinions, theres no question which way I'd go. SU's are good carbs when they're right, they work real well, but they don't even get close to metering as well as FI EVER. Fuel injection makes the motor last longer just by not dumping so much raw gas into the oil. Thats why its not uncommon for cars these days to run 175-200,000 miles, when years before at 100,000 they were getting tired and nearly always needed a top end job by about 90,000 (speaking domestically here). Just an opinion, but the drivibility, fuel economy and less wear on the engine makes it way to strong a case at least for me to even consider SU's. *Shrug* Regards, Lone Quote Link to comment Share on other sites More sharing options...
johnc Posted July 8, 2002 Share Posted July 8, 2002 Given a clean slate to start with, I would always go with FI over carbs. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted July 8, 2002 Share Posted July 8, 2002 Heheh what an interesting trend... on these boards so far everyone recommending FI, and I posted the same question over on Zcar.com, and over there everyone saying hands down SU's. I myself am also leaning towards EFI, but I'm probably a bit biased by all these problems these worn SU's have been giving me! On the other hand, I know my ZX's FI system is getting old, and I worry that though it may work perfectly when I first get it in (if I"m lucky), that it still may just be a problem waiting to happen. And I know that for the most part, fixing or even diagnosing FI problems is not cheap. With so many sensors and so much wiring and so many things that can get messed up.... yikes. Also putting the FI will most likely be the most expensive option right off the bat, as I've been quoted estimates of $600+ for the labor, assuming all my parts are still there and in working order (I'm starting to wonder...), as opposed to $600 for the new Ztherapy carbs, minus $150 back for the core charge. And those I'm relatively sure I can put on myself. Well thanks for the insights guys... keep those opinions coming, please! Quote Link to comment Share on other sites More sharing options...
Guest bang847 Posted July 8, 2002 Share Posted July 8, 2002 carbs.. Quote Link to comment Share on other sites More sharing options...
David K Posted July 9, 2002 Share Posted July 9, 2002 carbs.. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted July 9, 2002 Share Posted July 9, 2002 Just imagine the looks on the Honda guys face when you wax his butt and he accuses you of having a V-8, and you pop the hood, and all he see's is MOTOR, and two little carbs. FI is the way to go, but SU's rock. I may change my mind after I get them up and going, but I kind of just like the nostalgia and all. Quote Link to comment Share on other sites More sharing options...
Guest sball Posted July 10, 2002 Share Posted July 10, 2002 EFI is great for smooth running and perfect tuning, but when some electronic gismo goes, you're stuck with a bill, although SU's are not as easy tp tune or can't be tuned to the same efficiency, they keep on running year after year and for me, give me an excuse to go into the garage and play (wife timeout) Quote Link to comment Share on other sites More sharing options...
katman Posted July 10, 2002 Share Posted July 10, 2002 Carbs are just a semi metered fuel leak, and this is especially true of SU's above 4000 rpm where the slides are slam up against the top the whole time. Yeah, batch fire EFI and other early systems weren't perfect, but I agree with JohnC- given a clean sheet EFI beats carbs every time. And personally I'd rather troubleshoot a bad sensor on EFI than worn throttle shafts/improper float height/worn needles/worn slides etc. on an SU. Much more clear cut as to what your problem is. Of course reaching down into a hot place to twiddle with the SU mixture knobs has some real world applications which are not without merit... Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted July 10, 2002 Share Posted July 10, 2002 I agree, what error scanner can you plug into a SU that will tell you whats wrong with it? As far as sensors going out and such, most of them will cause it to run in limp mode at least until you resolve whatever it is, a SU won't do that, it either starts or it doesn't. I don't believe I've heard of anyone that went with like a aftermarket system like the SDS, TEC or Haltech ever wanting to go back to carbs for the 'drivablity and performance'. Its been 25 years or more since the manufacturers have gone to EFI, I think after all that developement time, its safe to do likewise, think about what causes most desktop computers to fail, hard drives, mechanic beast, bad... Electronics good... An opinion for sure. Regards, Lone Quote Link to comment Share on other sites More sharing options...
Guest bang847 Posted July 10, 2002 Share Posted July 10, 2002 bastaad525, Man replying to you almost sounds insulting.. (i mean you name and all) Well I think the way your looking at it is sort of skewed.. go with Z therapy carbs... they are the best and most expensive... go with the lowest bidder to install your FI... that could be the worst... I dont know too much about aftermarket comps for FI but IMHO.. your not comparing apples to apples... maybe you can compare the cheapest carb rebuild to the cheapest FI install... or compare Ztherapy's to a haltec... think about it this way... those carbs IMO dont need a ball bearing shaft as much as they want you to believe... i mean they have been running for 30yrs!!! well.. think about it... call up David... he gots my carbs.. seems like he like them... he is in your area anyways if you dont mind a 1hr commute.. Quote Link to comment Share on other sites More sharing options...
Guest bang847 Posted July 10, 2002 Share Posted July 10, 2002 David!!! just out of curiosity... did your fuel economy go straight to hell after the carbs??? I ask because I drive a l24e maxima too and it gets about 23mpg... while my 240z is not predictable at all... sometimes 15 some times 22... but I gotta say the SU's when run daily are very nice.... Quote Link to comment Share on other sites More sharing options...
johnc Posted July 10, 2002 Share Posted July 10, 2002 Back to the original question: > Which will produce the most power and best > reliability and driveability? I need advice! FI. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted July 10, 2002 Share Posted July 10, 2002 Originally posted by johnc:Back to the original question: > Which will produce the most power and best > reliability and driveability? I need advice! FI. the most power and the driveability is a two diffrent thing isn't it? I'm sure the SU would make more topend power but with narrower powerband. FI will be more driveable and with wider powerband. My 78 is pretty reliable after I got all the electrical bugs out. It cranks every time cold or hot. Quote Link to comment Share on other sites More sharing options...
David K Posted July 10, 2002 Share Posted July 10, 2002 bang my fuel economy is better tha my F/i was. I go on forever, a few days, on $5 of gas. also i havent found a replacemetn set of carbs yet. email me and send me your # at home or cell. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted July 10, 2002 Share Posted July 10, 2002 the most power and the driveability is a two diffrent thing isn't it? I'm sure the SU would make more topend power but with narrower powerband. FI will be more driveable and with wider powerband. My 78 is pretty reliable after I got all the electrical bugs out. It cranks every time cold or hot. The most power and driveability comes from FI period. Just like John said. FI doesn't necessarily mean the factory FI, which can be tuned for a large amount of power, but not easily or cheaply. However, my ZT with a factory '87 ECU gets 27mpg on the highway, and puts 230hp to the ground with no driveablilty problems whatsoever. Try that with a carb (blow-thru or draw-thru, carbs on a turbo suck). Quote Link to comment Share on other sites More sharing options...
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