Chino 240Z

Yep, It's what you said! But it's not until after I build the whole puzzle that I can see the picture, but it all makes sense now. I need to know what happened, why it happened and how to keep it from happening again. It's amazing how many people at the track that work on cars look at these carbs and say "what the. . . ", wish ya luck and walk away scratchin their head. Oh well, hope I can pass some info and help on to others someday. Cheers :classic:

Okay, so here's the deal with the SU carb problem. Finally had time to get back to them and after talking with Z-Therapy about the problem of both going bad at the same time, and I purchased their tape about SUs (Just SUs) I can't believe how cool these carbs are. The results: Both floats where way-outta-wack, flooding or as Cindy my wife said "drownding" in fuel. But how? Well it was a very hot day, and just after a 1/2 hour of pushing it hard on the track, the heat from the engine, headers, and the outside temp., the fuel expanded enough to push the fuel floats to their limit and I not knowing where they should be I could not get the flooding to stop. What can I do about it? 1.) I learned that they should be about .55" or 9/16" from bottom of lid to float while holding upside down and the float gently resting of the needle valve or grose fuel valve. Bend the metal tab slightly to bring to proper measurement. 2.) I have a heat shield and wrapped headers but that may not be enough to keep the heat away from the fuel bowls. So before shutting off the car, turn the fuel pump switch off first and let the engine idle and bring down the fuel level in the fuel bowls. Therefore if it gets too hot it won't heat up the fuel in the bowl so much that it pushes the floats out. 3.) Some people even cool down the carbs with fans, cool moist rags on carbs. & bowls or what ever with hood up after they have parked the car. I need to find a program that works best for me. But knowing how the carb works and how to drain the fuel out of the drain plugs on fuel bowl, and adjust float, fuel mixture nut, nozzle jet and main needle will get me out of trouble and back on to the track. Well, I feel a little smarter now, which is rare, and I think these dual SU carbs are what I will go with and put the triple Webers back on the shelf for now. Oh and Steve at ZTherapy nailed my problem on the head 1st time. They do sell beautiful refurbished SU carbs, rebuild kits, and individual parts that you might mess up while tweaking on these carbs. The SU video tells it all! Thanks Craig

If the knurled nut with ball bearings imbedded in them have been adjusted and you don't know where they are? you can start from scratch and then fine tune them. And that would be to close both of them by turning them up until they stop, then back them both open ( or down) to 2 - 3 full turns. I set mine at 2 1/2 turns. The ball bearings that you see are there to help you count your turns and help see how much you have moved the knurled nut. Set both the same amount of turns. Now with the car running you can now adjust them open or close a little at a time to find the fastest idle. To far one way will start to rough up or slow your idle so then you bring it back the other way and the idle will increase and smooth out until you have gone to far the other way. By closing it you are leaning it out, and by opening it up you are riching up the fuel. To much either way will slow and rough your idle. So by working it a little at a time you can find the best & smoothest idle. This should give you a good point to start fine tuning them. I would probably run it a little rich rather than lean, more engine damage could result from being alittle lean than rich, or wetter. You also should check the butterfly valves inside the the carb. to see that they are open equally, and a base starting point would be just cracked open tiny bit, the vaccum should pull enough air in to get it started. The Uni-sync meter will aid you in adjusting the butterfly opening so that the air flow in each carb. is the same. But these steps were the basic steps I took to get the carbs back to a starting point where I could get the car to at least run. From there begins the fine tuning. Good Luck Craig

Hey the Video was the best $20 bucks I have spent in a long time. I got the 2 tape version, the single tape is only $15. I have got through the 1st tape and went back out to the car and opened up both SUs, cleaned up things, made the adjustments, pre-set the idle and mixture settings and fired her up and varoom she was doing fine. It was very late and the neighbors were asleep, so when I get time to make the final adjustments I think I good to go. I think ZTherapy has the unisyn flow meters for sale for around $30-$40 frog skins, I need to get one too, so I can finish up the tune-up. Hey Mr. Killer240, that is not easy typing all that. I think tuning is actually easier than typing all that huh? Thanks for listing all that information. I have purchased 2 books on SU carbs, found a shop manual from a Datsun mechanic from many years ago (we found it in our neighbors garage while cleaning it out to help him move) also printed up lots of info. I found on this site & others and now the ZTherapy tapes, our library has grown alot overnight! Now that I got my problem worked out i need to go back and finish up my thread about the SU carb problem I had at the track the other day and why it happened. Talk to you later. Craig :stupid:

Your cell project is moving along good. Are you running the fuel line through the car or under the car through the tunnel? What is SCCA rule on fuel line through the car? I have been using the Holly Red pump (which I think is now colored silver or something but still called the Red pump?) and I can still see 5.5 to 6 psi up front, but I knock it down to 3.5 to 4 psi with the Holley Press. Reg., but I don't have custom needles either. I don't know for sure, but I recall the Blue Pump not recommended for continuous use or daily drivers. Short runs or drag racing and as high as 15 psi., so what is the life on a Blue pump anyways? Have you seen one go bad? Regards Craig

Not a good picture but maybe it might give you an idea of the finished install? This one is a 12 Gal. unit. One line is fuel a line to the pump and the other is a vent line to the outside of the car. Fuel cells can be messy if you spill or drip fuel inside the car, but in a race application, usually door windows are removed for safety, and you don't get fumes buildup, but that High octane sure has a sweet smell . . :lick:

Excellent thought, but we do have a press. regulator. From the fuel cell it goes to a large Fram filter, a "Red" Holley pump, then a Holley press. reg. and it's set for about 4.5 to 5 lbs, I have a guage and an idiot light watching the pressure. After sitting on the patio last night and talking about what's in the SU carb that can go bad, and there is not much! But. . . the float needle seats are rubber, like O-rings and can dry out as it ages, perhap they cracked after the run in the heat, and it has been sitting for someting too. So tonight I'm hitting the Nissan Dealer up for some SU carb rebuild kits, and we'll take a look. One reason why the previous owner went from the Webers to the SU carb is that in a hard long turn on the track he notice bogging and loss of fuel from the Webers. The fuel bowl is more square and flat on the weber carb and has a problem supplying fuel in a constant turn. The fuel bowl on a SU Carb has its fuel bowl seperate from the carb and is more of a bowl, round, with its fuel supplying from the bottom of the bowl then to the carb. Drag racers like Webers, no turning. I think I will stick with the SUs for now and rebuild em. I'll let you all know how it goes and what we find, and I say we because my wife warned me not to do it without her. Get this, she is an Reg. Nurse and is into cars as much as I am. Decorates the home in NASCAR, and demands seat time at the track too, Cool Deal huh! Later Craig :classic:

Thanks for the replies people! I agree about the Webers, the benifit of more Air/Fuel. Very few people ever get triple webers dialed in right. I use to run dual 48s in a VW sand rail years ago and at times talked back to me. I do have confidence in my help with the carb problem. Just want to go in half way educated before ya know what I mean. The other thing about Webers is they may need re-jetting when there is some change in altitude, but I don't think I need to worry to much as the tracks we have lined up are in So. Cal and San Francisco area. Heat Shields? Yes we have put some tin heat shields below the carbs and also have the headers wrapped too. Boiling fuel may be a short term issue, but these silly things are still spitting back at me today. Vent? We have the vent hose coming off the top of the "Fuel Safe" fuel cell vent and to the outside of the car. Has been the same for years. I believe the cam is an Isky cam so it has some lift to it, Nissan rockers & valve train and the head is an E31 but not milled. I like the idea of these Webers and the flow that will come from them, and I agree that though touchy, Webers should be okay since it isn't daily driven. On the other hand a back up set of SUs ready for just in case, is security for expen$$ive track time. On the Electrical side of things we had just installed the MSD6AL ignition system, MSD High Vibration Blaster coil, NGK Iridium plugs, and Taylor 8mm Spiro Pro plug wires, so I feel we have that side covered. Oh-well part of the fun is the search for the answers to problems like these. And part of the pain is this gotta fix it NOW addiction! ha ha We'll keep ya updated on how it goes. Thanks, Craig & Cindy

This weekend at the track, the Dual SU carbs had a problem, after a 1/2 hr. session on the track and a 45 min cool down period, tried to start car again and then started fuel flooding from both carbs at the same time. Shut off fuel pump, check press. regulator, and also check floats & needles all okay. Dribbling fuel from both carbs, too flooded to start. These SU carbs had lots of work put into them before I got the car, needles raised, jetted, polished, ect. and dependable for previous owner. Could both diaphrams or something internal go bad in both carbs at the same time? No gas additives, 76 Cool Blue 100 octane fuel, and just tried using Marvelous Mystry Oil for the Carb oil. Always fired first time, everytime, but this time. I've owned car for about 4 to 5 months. Been debugging car and the rest of the car is dialed in, few quick spins around the block now and then getting ready for the track. This was the first solid run on the car for us. I have a set of triple webers, manifolds & linkage, and another set of stock SU carbs on a manifold, and also the set of SU carbs that are on the car now which are giving me problems. I'm headed next week to a shop to go over options. Question: Invest in rebuilding and tuning up the Webers (Which were once on the car, I don't know why previous owner took off?) or should I rebuild existing SU carbs and also the second set of SU carbs for a backup set? This is a track, road car only, no smog, and looking for performance and dependability? Input and comments are welcome, cleaning things up getting ready for the shop next week. Thanks in advance Craig & Cindy. :stupid:

Guess you gotta be careful doing it but. . . We're always careful right? I have detected vac. leaks by spraying small burst of starting fluid or ether around the vac. hoses, lines and fittings. When I notice an RPM change or difference in the way the motor ran there was a possible location where the vac. was taking in the ether. When you find a good leak you can see the spray evaporate very quick and a definite change in RPM. Also the deal with the moisture getting in sounds like the other place I would look too. Good luck. Craig :classic:

I just put in a set of Corbeau Forza seats in my 71. They are more for racing, price is about $220.00 each, but they look and feel nice! Corbeau makes a $60.00 sliding bracket that bolts to the bottom of their seats then into your stock holes. Well if you were closer to California I still have the stock passenger seat, no cuts, looks great, still firm, has it's orig. sliding bracket still, don't know what to do with? Some times you can find them for around $40. Anyone else need a seat?

Can you say "Parts Car"? :stupid: Too Bad! So Sad! Wonder if his fuzzy-dice blocked his view, cause it's still hangin out the front windshield!