Zedyone_kenobi

Yup the bowls looked very clean at first glance, I need to remove the fuel lines to ensure they are clean

Unfortunately I drained them prior to removing the bowls! DOH!

NOTE: I may need to find out when the needle and seat actually shuts off the fuel to know how right or wrong this actually is!

Here are my floats as they came out of my carbs Front float: Back Float: Okay, not if I am not mistaken, the SU video says I need .55" of clearance between the level lid cover and the bottom of the float... Does this sound right. I have about .190 no the front and .210 on the rear. The pictures I am looking at shows the float hanging almost level when adjusted properly. If it is that off, then it would explain why no minor tweak of my mixture ratio nut would make a bit of difference. Now if this is normal, I may have to do one of those clear hose tricks you guys have mentioned. Is there a preferred way to check float level. I am about to do a search to get educated. My factory service manual says that dimension 'H' should be about .55" but it does now show where dimension H is on the picture! This may be a key piece of the puzzle!

Okay folks, I decided to try to swap out my SM needles for some OEM needles from Z Therapy. I got the mixture at 2.5 turns, which is close and it is actually doing a similar thing as before, maybe worse, but it is close. I was still able to pull to red line if I floor it in second, but anything part throttle just pops up a storm out of the exhaust. I am going to pull the float bowls this afternoon after the car cools down.

nope, I forgot about that, but I have tried that before. Funny though, I have no idea if it helped or not.. I do not remember.

Well went for a test drive, and it is still popping through the exhaust. I will recheck everything balance wise, and mixture wise in the morning. I will also probably change needles, even though I do not think it will make a bit of difference.

about 2 seconds is what it takes to push them up. What I did find that both my screw valves that act like a damper in the SU oil are both exactly .348" plus or minus many half a ten thousanth. Very close to each other. I took off the first carb dome today and cleaned the begezzus out of it. I used some gun cleaning towlettes and a good thin plastic pushrod. I cleaned every where there is metal to metal in close proximity. It went together and the piston acts like a mirror at all times to the rear carb piston with the exception of one thing. WHen I push the piston ALL the way up, it took the front piston a good 4 or 5 mississippi's to come down.. while the back one dropped right away. In an any other position, the pistons dropped identically, but all the way up, the front SERIOUSLY lagged the back. This may explain why my car only stuttered, at high rpm, at part throttle, and while changing throttle positions. At wide open throttle it would just go open and not have to adjust... So long story short, I took everything apart again and cleaned it up including the oil that was from the overfilled front SU oil reservoir and whala, the pistons fall at the same rate even from the very top of the stroke. I got my stock SU needles in but have not touched them yet. Only going to change ONE Thing at a time. I have high hopes that this may have fixed things. Perhaps my tolerances on my piston and dome are such that any liquid contamination at all was making it hang up. This is going to be interesting. If this does not work, I will let you guys know, and then get that O2 sensor installed ASAP. I will also try the NO SU oil trick and see how it acts.

Great advice! Thanks Captain! Just so you know my SU's are very hard to push up and they do leave a noticeable dent in your finger. Check valve okay. My standard needles have arrived, but I am going to try to clean the damper and dome more thoroughly today. That really seemed to help out yesterday. It was Steve91tt idea, and I think it paid off. I ordered an innovative O2 wideband yesterday as well. I will get that welded in and the guess work will be over when it comes to what is happening with my carbs.

Just want to thank steve91tt for coming to the house today to give me a hand. Just to update the thread. Steve took the dizzy with his pertronix out and we put it in my car and ran it with the same problem surfacing. Then we checked a different coil and it still happened. However, steve then suggested that we take a look at the pistons and the SU domes for cleanliness. Well they had some varnishing on them but nothing too serious. I cleaned them off and reinstalled them (first time the domes have ever been removed since I bought them from Z therapy). The car ran better with no popping until about 5500 rpm. Very clean running We also think we have the problem narrowed down to something in the domes, as the car will hold an rpm with little fuss, but the second I change the pedal position, it starts to sputter and pop out of the exhaust. Since I am VERY confident now that I was wrong thinking it was a timing issue, I am convinced it is a carburetor issue. Which means the time has come to increase the amount of data we have to work with. I will place an order for a real time wide band O2 sensor and we can further diagnose this issue. The O2 sensor will come to be more useful WHEN I get my triples one day, so it is money well spent.

Great work!!! keep up the momentum! I think you have a real fun project on your hands. Enjoy the drive man!

I checked my fuel lines and they are peachy. They are supple and are holding their shape well. I have not touched my float levels. I have ordered a standard OEM set of SU needles AND a set of float bowl gaskets from Z therapy so when I tackle the float levels I will be ready. copy that on the timing chain. I forgot my mechanics there. One more reason to check to see if the valves are adjusted correctly AND if the timing chain has any stretch. Can fix both at the same time. By the way, while I am thinking of it. I would think you should check for timing chain stretch while the engine is hot. But I have not checked. Is that the case.

MY car has 71k original miles on it. Since I am thinking that my issue lies not in my carbs but in my timing somehow,I was wondering if my timing chain may have some stretch in it, which is not allowing me to time it right. But I am not sure if that would make me run advanced or retarded. I will have to think about it. Nevertheless, I need to pull my valve cover and check to see where the heck I am when it comes to timing AND valve lash.

Merry Christmas guys, and happy new year. My God bless each and every one of you with health and happiness in 2012

I will check for you, but remember I had it recurved, cleaned and had new bushings/bearings installed. , so it is nothing like stock any more. Still I wish I had an extra dizzy just to see what a stock one would run like. I need another data point. Just for kicks I installed a brand new in the box set of NGK plug wires and a new cap. Still does the same thing. These plug wires have a 5 kOhm reading, were as my taylor wires had a 0.740 kOhm reading. Car ran exactly the same. Last thing I did was advance my timing to 17 degrees static and I will see how that runs tomorrow. I have yet to hear any pinging so I will do that. If that fails I will order a new valve cover gasket and take a look at my cam shaft. It is possible that I may have a worn lobe, but I honestly think that is highly unlikely.

tomorrow morning first thing I am going to do a compression test... I did one 3 years ago, but we have to check it off the list.

yes, brand new cap and rotor. Well less than 4 month old and 400 miles. I advanced my timing to 17 degrees static now which should yield me about 36 degrees total advance. Which I think is plenty. I did order new float bowl gaskets today and some OEM factory needles. We will see how they act if I need them. Today I experimented with my mixture. It still pops profusely at part throttle, Here is an interesting tidbit. As long as the rpm is increasing it seems to barely notice anything, but when I slowly creep up on about 4000 rpm, it spits and sputters if I hold it there. How about some SU help here. During acceleration the pistons rise, but when I reach the tail off of the acceleration, I would think the bowls would drop. Could my bowls be dropping way to fast, causing lean spot? OH I run standard issue SU oil that MSA sells. No idea what weight it might be. It came in a clear bottle called 'SU oil'

wow, less than one turn! My car would not even run like that... amazing how different two mostly stock cars are..

motorman, glad to know there is somebody else chasing this issue. Were you popping out of your exhaust? Can you tell us your stats? What initial static timing are you running? Max advance? Are you seven eights turn form full lean? Or are you 7 to 8 turns from full lean? You lost me at your mixture screw setting? Also is your motor stock? The more data points the better. OH, I forgot to mention, I only run 93 octane Chevron in my Z.

Welcome welcome! I do wish you the very best luck in your search. I hope you find one that lights your fire as much as your first Z's did!

copy that, I checked mine out. Mine flows in the direction it is suppose to flow. I cleaned it up and reinstalled it. Today I may be grounded. It is pouring rain out side all day and I may not get a chance to go for as spin. Sort of irresponsible to do wide open pulls on a wet road! So here is where we are at. Carbs are at 2.5 turns from full lean. All my choke cables do return to the right spot. Needles rise and fall with no binding what so ever I have good fuel pressure Timing is at ~15 BTDC Vacuum Advance is installed but not hooked up PCV valve is clean and operational NO vacuum leaks of any kind These are my symptoms: Car starts idles and drives perfectly up to about 4000-4500 rpm Under part throttle of any kind that takes me above 4000-4500 rpm I get popping and misfiring through the exhaust Under wide open throttle in second gear anyway I can get the car to pull all the way to redline without hesitation With the vacuum advance hooked up The part throttle symptoms are still there and may be worse What I have tried: I balanced the carbs 2 different times, they are spot on I checked PCV valve I installed new plugs I installed a new fuel pump I totally rebuilt my entire fuel system I had my distributor rebuilt and recurved to european specifications New Z therapy carbs with SM needles I have run with the vacuum advance and without it I have tried timing from 8 degrees to 15 degrees I have run a jumper from the battery to the coil bypassing the tach to see if the old tach is messing up my power to the coil What I have not tried yet: I have not tried to advance the timing more I have not swapped out my distributor or pertronix to see if that is at fault I have not done a valve adjustment I have not run more than 2.5 turns out on my carbs I have not looked at my float levels since I bought the carbs I have not bought a wideband to get real answers once and for all (after christmas I promise!) What I am planning to do! When it dries up, I am going to make a hard full throttle run on a long stretch of road, and then stop and pull the plugs immediately before the evidence is lost Analyze the results and make changes I may go more rich/lean by a quarter turn I will place an order today for stock SU needles from Z therapy and a set of float bowl gaskets. I will buy a wideband O2. NGK makes a nice one for less than 300 bucks. If I get desperate and I am convinced my fuel A/F mixture is close, I may play with timing more. Am I missing anything guys? Can you give me any more advice? I certainly appreciate all the ideas. This is truly a tricky problem.

nope, I have not done that...But the engine does not act like it is that far out of time. When I did my valve job 2 years ago I noted in my journal that the timing mark appeared to closely coincide with the TDC. But I can always double check. A wide band will have to come into play eventually. So man variables to consider. I have to be able to concretely nail down some of them with data.

I can do a valve adjustment Friday. I am taking off that day. Can anybody with a stock 71 tell me what kind of max advance they are running with the stock cam at say 3000 rpm? I did not touch the timing today. I am still at about 15 degrees static. Max around 32. As I was yesterday. By the way folks, thanks VERY much for the help. I usually try to be the one helping others, but now I really need the wisdom of the Z gurus.

Ah, I never really looked that hard into that. Yup, That goes to my crank case ventilation, check, PCV valve is new when I got the carbs. I removed it and it rattles when I shake it... I will check to see if there are some diagnostic checks I can do on it.

There is nothing at all on my balance tube. It was all taken off when I got my total Z therapy treatment. Another piece of the puzzle. I went out for a drive today after work and fiddled a bit more. Set the carbs at 2.5 turns out which is where they were at, NOT 1.5 turns out, I misspoke earlier. As I wanted to be sure I checked them and set them to the 1.5 turns out from all the way up and the car would not idle. I knew that was wrong as my car always had an awesome idle. So I put them back to 2.5 turns and BAMMO, rock solid idle again. Also, the popping only occurs at part throttle at around 4500 rpm. At full throttle it pulls hard to 6500 rpm no issues. Interesting problem!