madkaw

Well after running the engine again and seeing #4 draw much less air then it's next door neighbor#3, I decided to rip them all off and pull the intake too. Of course the intake gasket was fine, which I thought it would be. The car didn't run it had vacuum leaks, but I'm getting desperate. I did check the butterflies on 3&4 and they matched up beautifully. Now I stare at my engine thinking what;s next. Not much in the way of evidence to justify pulling the head, but I think my carbs are okay. I did notice looking down in the intake runners of 3&4 that there was a lot of soot? on the inner walls of both cylinders. When I say inner, I mean in respect of each other. No other cylinders look like that. Kenny, I fought transition with these carbs and thought I won with the bleed pipe mods. I don't think those mods have anything to do with my issues now. I would try and go as big as possible on my pilots if I were you. I don't understand why my motor/cam wants such big pilots, but it works well. I think it is mostly the Schneider grind, but I've run 70's on my motor. I run 67.5's now and it's just a L24!! The bigger pilots might help you bridge the transition gap better, then maybe drop your main air's. I have smaller main airs if you need any. I bought all the way down to 160's to fight the transition issue. I'll never use them.

It seemed that a fatter idle made for easier start ups for me, but if you can get away leaner-go for it. Don't forget Mitchell, he is boosted. Want to keep things on the rich side.

The short answer -No:( I messed the carbs all day. After seeing #2 looking fouled I decided I needed to tear them all down and put some compressed air to things. In the process I didn't see anything that I could attribute to any of my problems. There was the slightest bit of sediment in the bottom of the carbs. I put everything back together and and got it running. It's still not right, but once again I can put my finger on it. When I went to synchronise the carbs #4 was hardly drawing air compared to #3. It was off by quite a bit. The engine didn't idle to terrible, but not like it used to. I finally just said WTF, I'll drive it and see how it feels. Well it still not right, hell it even back fired once getting on it. Seems to be lacking power . The AFR's didn't jive with the known jet settings and they seemed a bit erratic. I pulled the plugs afterwards and none were fouled and they didn't look too bad . Not sure what I'm going to do next. I will probably drive it again tomorrow weather permitting. Getting really discouraged and pissed with the whole matter. This seems to be dragging on to the point that i don't remember how I got here. This car used to run fantastic.

With these cars - value is in the eye of the beholder. Now if you were dropping a v8 in a Ferrari- then you might worry about values

Wow- hope it's worth the wait! It seemed forever to get my engine done locally, but in comparison I guess it want too bad. But my head was serviceable ! Just grabbed another e-88 for spare too!!

So a little history please. Was it running fine before? Might just start looking at the basics and going from there. Check for tightness of all fasteners , return springs , linkages.

Seems okay and working right are two different things. If he worked on Datsuns he knows that these dizzys screw up --a lot!! Simple test to accomplish - pull vacuum hose, plug, drive:)

You might be on to something with wanting to check the dizzy. Those years are prone to issues regarding the vacuum advance. You might try disconnecting the vacuum portion of the advance and try driving it . The plastic parts of those dizzys break and cause the vacuum advance to malfunction . Check what scale you are on with your ohm meter. You were probably reading 2.7 ohms

I don't know if I would say that about going back to 70's technology. FAST is no joke engine management and there is probably a lot of support available on that general systems. The FAST system would be worth making work. Any wiring for the chassis for a 73 should be a pretty simple task.

Definitely not your ole carb tune stuff. I guess if it runs good it would make a nice platform to finish up . It's always a bit of a gamble on a performance modded car like that. You have no FSM to fall back on. If you have a strong mechanical background and don't mind chasing wires, you might be alright. Since the price seems based on a performance upgraded Z - it would have to run and drive good for that money .

Don't forget that having the crank in a certain position allows for more clearance when wedging pan between the crossmember .

Find the download for the FSM for the car and get your ohm meter out and start checking everything . CHT comes to mind for your issues.

Your mention of solder was noted and it has been on my mind. I know my bleed pipe alterations are still in tack, but wonder if loose solder from previous attempts have made their way somewhere not good. I tried to be careful but might have gotten sloppy and not cleaned up properly and now have solder blocking a passage. I'm not too far from breaking the carbs all down anyway. Cursory inspection shows clean as a whistle

Jim, I appreciate all the input-truly. Not sure that isn't one of those deals that I have made worse by trying to fix the wrong thing with an adjustment here or there. I will eliminate the possibility of a faulty fuel pump when I get back to town . I will do volume test there. I also need to make sure any linkage issues are resolved. This has just been a total kick in the balls for this summer. Too many nickle and dime issues already and this just takes all the fun out of my hobby. Thought I would be at the dyno by now and pushing forward on my custom FI project. Hopefully walking away will reset my attitude. I about have to take a week off since the family is going to CA for a week.

Magna flow turbo . Go as big as you can fit. I'd run a second resonator and run all 2.5 or 3" pipe

Don't forget your springs. I bet you have custom springs for that cam.

Not conclusive or thoroughly investigated , but though it is a problem I don't think it's my overall issue. I only had a little while to play after discovering this, but it wasn't the night and day difference I expected. The jury is still out. These carbs did/have run beautifully with te response of a sport bike when blipping the throttle. I would never consider cable option as well as throttle feels and works. Another thing I noticed and don't want to read too much into is the amount of condensation dripping from my exhaust. It hasn't been that humid here but I have been doing a lot of idling. The drips don't seem to ever stop. Looks like water only.

I've watched my fuel pressure gauge when i can(in the engine compartment),but that might not tell me if I have a flow problem.Nice thing about the MS is I can turn my pump on without running the car. So I will measure that next to make sure I am getting adequate flow. It makes me think pump when I watched the AFR's slowly bobble to the lean side. I did discover that my rod linkages needed work. I was just flipping the throttle while leaning over the fender and noticed the levers not at the same exact moment. In fact one of the ball socket ends is worn which allows for movement without throtlle action.

It hasn't been a very good week and the Z doesn't want to run right. I have actually been able to find time to work on it, which usually is a problem. But after hours of troubleshooting and working on the car I seem no closer to an answer.It's one of those troubleshooting nightmares that has caused me to walk away before I do something stupid----like give up Z-ing. Symptoms are erratic and only sometimes can I duplicate. I am scratching my head and loosing heart and motivation. I love my Z, but it hasn't been fun lately just working on it while we have had the best weather all year. I will try and describe my issues-though it will sound vague; I have been around the world and back so my descriptions might seem lucid. The engine sounds like it has a miss and won't idle as smoothly as it used to. It feels down on power. Laboring might be a good description of the idle. At first-- cylinders 4-6 seemed to be the culprit. Plugs looked dark and #4 was the worse. But how does half a mikuni run rich? I also had number look dark, but for the most part, everytime I checked 1-3 looked lean or no color. Now most of this has been idle time in the garage, but those general plug reading were after a drive also. I have seen the plugs 4-6 look both clean and dark during all this troubleshooting, but #4 has been the most consistantly fouled. My AFR's bounce around quite a bit at first . I have dual exhausts so I only have the O2 sensor in one side or another. At first the sensor was in cylinders 1-3 and the reading were not bad, but erratic, not stable at idle. it would run at 14 and start a bouncing routine and then look lean. I switched the o2 sensor to the rear bank and it was pig rich-like 10.5-11 at idle-hence the dark plugs. I had to turn the pilot screws on 4,5,6, in a 1/2 turn just to get the AFR's to 13.5. Keep in mind that my jetting is at a known good setting that has worked great before. I've ran these pilots jets and screw settings with no issues before. I have checked floats and they are spot on. I have pulled the covers after running and they are all at the same level. All my pilot screws were replaced and all the tips are in excellent shape. I suspected ignition or my Megasquirt because of the randomness of the issue. But I replaced all components with a 280zx dizzy and wires and no change. Replaced the plugs too. Ignition timing checked with the dizzy and the megasquirt. I checked all valves and adjusted as necessary-nothing to crazy. Vacuum guage only show.ed 12HG at idle taken from a port on my vacuum log. I thought that a bit low. Sprayed everything down with started fluid and could find nothing. I removed the complete vacuum log assembly and capped off all port openings. So there is nothing hooked to the intake. Checked torque on intake bolts and noticed one exhaust flange nut very loose at the very end of the header. I hooked up a coolant pressure tester to see if pressure was building anywhere --- as in a bad HG. I set the tester at 13psi, the same as the cap and pressure rose slightly to 15psi and stayed. No bubbles in radiator and level seems to be the same. Nothing in the oil. Compression test done 1-205 2-205 3-205 4-215 5-205 6-210 Not sure what to make of those readings, but cylinder 4 jumps out at me a little. I'm pretty sure these are within percentage limits of each other. So I proceed to switching out carbs. I swap the 3&4 for 1&2. I run the car and bingo, #2 is now fouled-I found it. #2 would have been #4 cylinder so it must be one side of my carb. So I switch out pilots, and e-tube(which should have much to do with idle). Now #2 isn't fouling, but the engine still idle like sh!t. I should say that I checked all the O-rings when I had ALL the carbs off. This is what i meant about nothing being conclusive or concrete. I have run and cleaned plugs several times and nothing seems very consistant. I had to walk away after about 10-12 hours in the last two days. Not sure if a bad intake gasket would cause such issues, or a avccum leak in general. At first my gut said HG, and I'm not totally convinced it's not, but no definite eveidence to warrant pulling the head off. Valve timing? Well it's not so easy for me to determine this. I have an adjustable sprocket and I degreed this cam in many moons ago. I will have to really ponder on how I will check my valve timing. I have looked down in the hole to see if my chain adjuster popped out or something, but didn't see anything alarming. Could the chain jump a tooth? Unlikely if not impossible, but there is no quick way for me to determine this. My gut says HG or Valve timing(ignition is safely eliminated), but don't want to go on a gut feeling. Give me some ideas guys

Thanks-keep any ideas coming. Chokes-maybe-but I would think it would foul both sides are carb, and I did check them Jets have all been used before with no issues. I could swap around e-tubes I guess. Not sure what could go wrong with them.

I need some insight here guys. Having an issue with running rich on certain cylinders. Primarily #4 runs rich, but 3 is fine. How does that happen that one half of a carb runs rich. Floats have been checked as well as fuel pressure. Ignition has also been eliminated from the equation. I also did a coolant pressure test for a blown HG. Cylinders read 180-190 on cylinders 4-6 Getting ready to pull carbs off completely to look everywhere. These carbs have been very consistant as far as pilot adjustments, but now I have to turn #4 way in to keep it from fouling out. I will be blowing out passages to I guess. I have been having the biggest issue with cylinders 4-6.

I would comment that my direct linkage works flawlessly. I couldn't imagine cable being any improvement. It can be done!

I believe that depends on what e-88 head we are talking about. An early e88 with bigger valves will down around 41.5. The earlier head will not be a fully OPEN chamber like the 42 or 47 head.

My observation has been the opposite. Engine purrs and sounds so much smoother with a rich mix. Exhaust sound is fuller if that makes sense. I really don't think these carbs were designed for lean driving. Probably has much to do with the Tau layer. Love my Mikunis but ready to tune without my hands smelling like gas

From all I have read-don't go with a thicker gasket to lower compression. Keep the squish tight to fend off detonation. So far good luck with my Nismo 1.25mm