Guest Nic-Rebel450CA Posted July 3, 2003 Share Posted July 3, 2003 Ok, I have searched the forum, and search online for the last couple days and I cannot find any diagrams telling me where the adjustments screws/nuts/nobs/monkey arms are on these carbs I have found plenty of walk-throughs for tuning but they all seem to assume that you already have a knowledge of the carbs! Does anyone know of a diagram somewhere online that has a pic of the carb with parts labeled in some way? Can someone maybe make me such a diagram? BTW, I would be happy to supply pics of my carbs if someone can diagram them for me. Quote Link to comment Share on other sites More sharing options...
DAW Posted July 3, 2003 Share Posted July 3, 2003 The easiest way would be to go to Barnes & Noble and pick up one of the books on SU carbs (or at least flip through it to get the info you need). DAW Quote Link to comment Share on other sites More sharing options...
spotfitz Posted July 3, 2003 Share Posted July 3, 2003 Check ZTherapy.com They have some good descriptions of where everything is at, w/ pics. Quote Link to comment Share on other sites More sharing options...
zolorin Posted July 4, 2003 Share Posted July 4, 2003 Some very poor pictures in the Hayenes manual on p54-59. I will try to explain what each does There are two throtle position/adjusting screws (one on each carb) should be near the flange on which it is mounted on the intake manifold and on mine they are facing each other. You want to make sure that they are exactly the same number of turns from being closed. Best way it is done is by removing each carb (cleaning and some voodoo) is to set each throttle to 0.0232-0.0272inches using a gage wire which is in this range. There is a screw on the top called fast idle setting screw -- it does what its the names says sets the idle. For carb tuning just have it at the minimum Fourth Screw is the Balance screw located on the throttle rod which connects two carbs together. I will tell you about this one later last is the pair of screws that are on the bottom of the carbs and are on the jet. Screw them in all the way and then unscrew them about 1.5 turns Fire up your car (use the choke), let it warm up. If your rpms are too high without any help from fast iddle screw then rotate the throttle screws (both of them) exactly the same amount in the same direction to reduce the rmps (should be about 700) Then you use an airflow meter of your choice to balance the flow between each carb by using a ballancing screw. Your RPMS will change a bit so be prepared to adust them after moving the balance screw. You want similar flow to each carb at idle and then at 2000/2500 rpms similar procedure except you don't change the throttle position at high rpm and use idle screw to rev your engine. Have fun Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted July 8, 2003 Share Posted July 8, 2003 thanks for the help folks. i guess i'm giving up on these SU's they just wont balance. One runs like a champ, but the other just wont keep up. Prolly gonna switch over to FI now. Quote Link to comment Share on other sites More sharing options...
Guest DaneL24 Posted July 8, 2003 Share Posted July 8, 2003 Lets think about that for a second...which will be easier? Fixing the SU carbs or completely converting to EFI...hmmmmmm. Just get a manual for the car, it should have a decent section on the carbs. All the throttle linkage adjusting screws are pretty simple to understand. The throttle control for the front carburetor is set, the rear carburetor is adjusted to synch witht he front carb. There is a throttle stop screw for each SU, right above where the throttle linkage meets the carbs...and another throttle stop screw above the top throttle shaft. By the front carb is the throttle opener vacuum diaphram. It also has an adjusting screw that looks just like the carb synch screw, but its separate. I would just play around with the throttle linkage and look at it closely until you see how it all operates. The throttles for each carb are independent of the center throttle shaft, you can open one carb without the other by pushing on ieach carbs individual linkage. I just messed around with the throttle linkage for about 15 minutes and now I understand them great. Also, are your chokes adjusted correctly (Does each cable have the right amount of slack)? Do you have enough damper oil in each carb? How about the float levels (compartments to the sides of the carbs). The mixture adjustment for each carb is the round nob on the bottom. If you can't figure them out just by adjusting them...you may want to pull them out and rebuild them. Once you get them apart and see how its all put together, they should make more sense. And just buy a 240Z manual and study up on the carbs. They really aren't that complicated. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted July 8, 2003 Share Posted July 8, 2003 Check the carbs and manifolds for vacuum leaks. Spray engine starter fluid (the canned ether stuff) or propane around all joints. If the engine RPM changes when you hit a specific joint, then you have found a vacuum leak. With old SU's pay particular attention to the throttle shaft bushings. They wear out and cost big $$ to fix. Quote Link to comment Share on other sites More sharing options...
spotfitz Posted July 8, 2003 Share Posted July 8, 2003 For a temporary fix on the throttle shafts you can pack them with a heavy grade grease. As stated, it is a temporary fix. Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted August 13, 2003 Share Posted August 13, 2003 I have been tinkering with the carbs some more and checking out the linkages as suggested and I noticed that the linkage may not be set up right on the front carb, it looks like a spring is missing completely. I will take some close-up pics and see if anyone can identify if this spot should have a spring (it looks kinda like the linkage may even move backwards ?!?) Also, good news so far... The carbs are getting closer to balanced now that they are getting cleaner. When I got the car the air cleaner was literally black. Gonna try pulling the carbs off and clean them up real good and check the adjustments again. BTW, how will the car perform if there is a vacuum leak? My experience with vacuum leaks has always been that the car wont idle for anything or will stall or something otherwise obvious. I am wondering if my exhaust leak that I have been chasing is not an exhaust leak at all but perhaps a vacuum leak on the intake ?? Hmmmm Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted September 1, 2003 Share Posted September 1, 2003 Here is my tribute to a free digital cam. Actually these are some pics of my intake that I just pulled off. If you can at all make out the object that is circled in the pics, I need to know what this is. When I was pulling the intake off to start my hunt for my nasty leak (still dont know if it is exhaust or intake) I noticed that is "part" was threaded on and so loose it wasnt even snug. If these pics are too bad I will take some more pics with a much better camera. I also might be interested in taking a poll on how to do away with this p.o.s. camera that I have now Quote Link to comment Share on other sites More sharing options...
spotfitz Posted September 1, 2003 Share Posted September 1, 2003 I don't think you need a poll for if you need to replace the camera. lol It also appears you haven't checked ZTherapy.com out, or you would know what that "part" is and what it does. That "part" in your pic is the nozzle and nozzle housing. The hose connected to it comes from the float chamber. The level of the fuel in the float chamber (determined by the float) allows a specific amount of fuel to sit at the same level in the nozzle, in which the needle is inserted from the bottom of the piston. The needle/piston combination determine how much of that fuel enters the intake via, how much of the needle is in the nozzle. The choke pulls the nozzle down from the needle allowing more fuel to enter the intake at any given RPM. The only thing holding the nozzle in is the hose from the float chamber and a bar connected to the throttle shaft, which brings us to your pics. Here are acouple pics of the throttle linkage, courtesy of ZTherapy. (ZTherapy.com, btw) Ignore the captions in the second pic for this discussion, include the caption in the first pic(if the needle, the part you have circled, doesn't stay pushed up by itself then follow the directions in the first pic, "bend spring") . Both pics are of the same linkage, but different views(from what I can tell by the extreme close up). Once you've figured out what is to be bent on the front carb, from your pics and the ones I have pointed out then you can figure out what is to be bent on the back carb. BIG WARNING THOUGH! If you don't know what you are doing by bending the spring for more tension on the nozzle you can screw it all up, for lack of better words. ALSO, if the nozzle isn't even the problem, but the "part" the nozzle goes in is loose you will have to use the piston and the needle to align and tighten the housing("part") the nozzle goes in. Here is a very good close up of a 1600 roadster carb that shows all the components in proper alignment. For this discussion the pic works. The roadster carbs are almost identical to our Z carbs. You can clearly see the piston with the needle coming out of the bottom going down into the noozle housing. The idea is for the needle to drop freely to the bottom of it's travel without rubbing on the noozle, which is at it's highest point of travel. If it doesn't rub then it's ok. If it rubs then the nozzle housing("part") will have to be aligned using the lock nut, visible in this last pic just below the carb body. With carb in a postion like it would be on the car, loosen the nut, drop piston putting the needle into the nozzle, while nozzle is in it's highest point of travel and slowly tighten the nut. Now while holding the nozzle up, pick the piston up and lightly drop it in it's bore. You should here a clunk. If not, loosen the nut and start over. If you do hear a clunk then slowly raise and lower the piston and feel for resistance of it's travel. Keep playing with loosening the nut and aligning it until you feel no resistance in the movement of the piston/needle. Now you can put everything back together and adjust the carbs. If I just wasted my time on this very long post and you thought the needle wasn't suppose to move, don't tell me. Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted September 3, 2003 Share Posted September 3, 2003 If I just wasted my time on this very long post and you thought the needle wasn't suppose to move, don't tell me. Thanks for the post, I found it very informative. I dont know why I couldnt find this info on Ztherapy. I checked out the site a couple times but I could not find all of this info. Was it all under the roadster section? Anyways, I guess my carbs are pretty messed up. The pistons barely move. (takes a bit of pressure) and then one of them wont even drop on it's own. Sprayed it with some carb cleaner and that helped a little. Still fights quite a bit when raising the piston, is that OK? As for the bottom of the housing, I still havent found if the part I found was loose should be loose or not. (the part in your pic 3 that is round with the ribbed edge) Also, behind that is a nob which I think is the mixture adjustment and they wont turn at all (both carbs). Or is the round ribbed part the adjustment? Ztherapy just calls the nob that i am looking at a "flat disc". Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted September 3, 2003 Share Posted September 3, 2003 here's a better pic of one of my carbs: http://www.hybridz.org/phpBB2/album_pic.php?pic_id=1666 oh ya, one other question. Where the carb mounts to the manifold there is a thick block spacer (green circle). I want to take the carbs off the manifold to clean it up and maybe powder coat. Can this same spacer be re-used, or do I have to get new ones. (It appears to just be a metal block with gasket-goo on each side so I would think I would just need to re-goo it to re-use it) For my other questions, the Red circle is the part that I was saying was loose. The Yellow circle is the part that I thought was the mixture nob. And I have noticed that the big part in the Blue circle wiggles a bit too, should I tighten that down or should it have some play? Quote Link to comment Share on other sites More sharing options...
spotfitz Posted September 3, 2003 Share Posted September 3, 2003 I would HIGHLY recommend ZTherapy's carb video. It is very informative on the cleaning and adjustment of the SU carbs and informative on alot of other aspects of the carberated Zcar. I'm hoping you have everything clean inside and out of both carbs by now and hopefully you didn't mix up parts between the 2 carbs. Don't bother with taking anything off the linkage, just spray it with carb cleaner to get it cleaned. As for the piston not rising like it should, you may need to loosen the dome screws alittle(the domes or pistons may have even be switched from previous owner, but don't switch them, yet). Loosening the dome screws can help as I've seen the dampener shaft bent before. You should also have the dampener removed during the raising and dropping of the piston(sorry I didn't mention that before, this is the little black knob on the top of the dome). I assumed you would know that. Lets start with the nozzle and nozzle housing again. (look at the third pic again)At the base of the carb body there will be a nut, which should be tight and just below that there should be a spring with a finger grip knob(which should turn) and then there is the nozzle(the part with the hose connected to it) going into all of it. On some year model carbs there is a "flat disc", as ZTherapy calls it. This is nothing but a lock nut, basically. It does nothing more then keep the adjustment knob(finger grip) in one spot. You may have to loosen this to turn the adjustment knob(finger grip). The finger grip knob, just below the spring and above the nozzle(which has the hose connected to it), IS your adjustment knob for mixture. If looking down at the carb from above, you will turn this knob counterclockwise until it stops and then turn it clockwise 2 turns. If your needle in the piston is in it's proper place then your mixture should now be set. Leave the the dampener knob off the carbs, put the carbs back on and hook everything up as it was, except the air filter. You should now be able to atleast get the car running again. Put alittle oil in the hole where the dampener knob was and replace the dampener knob(I prefer Marvel Mystery oil). Push the piston all the way up to set the oil level. Start the car again(it may smoke for alittle bit). Email me or reply to this post when you get to this point. I'm always on here and will reply within the day, usually. Sorry, getting rather late and don't want to give you bad info. Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted September 4, 2003 Share Posted September 4, 2003 thanks everybody, (especially spotfitz) These carbs seem to be operating much smoother now and I am hoping that it will make some difference when they get back on the car. I am starting to get worried though because I am about ready to put the stuff back together and I still havent found where my darn leak is. Intake and exhaust side both look fine. I can only hope that the intake/exhaust gasket was the cause. Quote Link to comment Share on other sites More sharing options...
spotfitz Posted September 4, 2003 Share Posted September 4, 2003 BTW, I'm going to be selling my setup soon. ZTherapy polished SU's, K&N filters, ceramic coated intake and fuel rail. These are all sitting on the bench right now and I don't plan to put them back on my '74 because I have almost everything to go turbo, once I get her painted. I have over $800 invested in the setup. You can see a pic of the setup below. Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted September 5, 2003 Share Posted September 5, 2003 as much as I would be interested in getting a great setup like that I am trying me best not to put any real money into this engine because I just plan to swap it out anyways and I know I will never get even half of the money back. :| Quote Link to comment Share on other sites More sharing options...
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