First drive in the Z, Backfiring and sputtering.

[EScanlon]

I'm glad you posted again, as the specific part that goes bad is UNDER that plate with the counter weights and springs.

The counter weights and springs are the CENTRIFUGAL advance mechanism. (Someone correct me if I'm wrong.) This is what allows the mechanism to advance the timing of the distributor to allow for a given amount of timing advance as the engine is accelerating hard.

Below that plate lies a little plastic plate that has a few ball bearings held in place in plastic cups. That little plastic plate is what allows both the centrifugal and the vacuum solenoid to rotate and return SMOOTHLY. When the ball bearings or the plastic plate go kablooey, both plates function erratically. i.e. they "lurch" forward and back. This is what gives you that erratic sometimes ok, sometimes not ignition.

That plate falls apart after so many years, and so many Z's have had that problem that it's considered a typical problem.

I don't know that you can repair it. They ARE still available, in my case my mechanic was able to obtain one readily and replaced it. I believe he said they were in the mid $20's.

At this point, the disassembly of the distributor, I admit that I am getting out of my level of knowledge. Bambikiller, Beandip, 2ManyZ's, 1 Bravo 6, and Zedrally and others (omission by my limited thinking this A.M.) can no doubt give you better details as to how to reassemble etc. But I believe that you've found your culprit.

Enrique

[beandip]

Just for clairification , the vacume plate that has been mentioned is in fact two metal plates that have ball bearings sandwitched in between . The top plate is where the points and condenser are mounted . This the lower plate , which has notches in it , is where the vacume advance attaches. Now the ball bearings are held in place with plastic keepers , or should be. What usually happens is after about 30 yrs of service the plastic parts brake and the balls will fall out of position , and the advance then is all screwed up and cannot function properly. If the ball bearings are all in place and the keepers are still doing there thing , just clean all the dried up grease off relube and reassemble. These plates are available if needed from Nessan. The centrifugal advance , you can only just check to see if the springs are all there , thats about it unless you put the dist on a diagnostic , spelling , mechiene . This is how they recurve the advance by changing the springs. But that is another issue. I have never seen a condenser partically fail, ether good or bad . I hope this helps. Scanlon is right , look for the simple things first. I do agree that your problem sounds like bad gas as well. Gary

[messenger]

I made some progress today... well sort of. I put some new plugs in the car and once again it ran perfect.

There seems to be something wrong with the choke. If I idle the car on the choke it will run awful basically how it was running with fouled plugs. If I idle the car with my foot on the gas pedal at say 750rpm it idles nice and smooth.

The choke slides under the carbs seem to be returning fully. I would open then close them and try and see if I could push the slide in a bit more. They seem to go all the way in one would stay out about a 1/16 maybe. I lubed the slides and all the cables and pivot points. The lever in the car was easier to move but that is about it. I also added some ATF to the carbs they seemed a bit low on fluid.

After all this the car would still soot up the plugs after idling for just a few short minutes. The car has to be running to rich, but im not sure as to why?

I ran the car out a seperate gas can and it would soot up the plugs just as fast.

I think a carb rebuild is inline what do you guys think?

[EScanlon]

Ok, from that "good" idle, accelerate. Give it a good "hammer down" style acceleration and tell us what she's doing.

My bet, (Vacuum Advance Plate still shot) you get backfiring, stumbling and a VERY ROUGH and seemingly intermittent acceleration. Then when you release the gas, it seems to sputter, cough and not want to run for a few seconds before it "miraculously" seems to settle out. That the plugs are fouling may or may not be related to this.

Trust me, if you keep adjusting EVERYTHING ELSE before you fix THIS problem, you're going to have another $500 OBO E-Bay Project Car Auction with a tagline that says "Several years ago, I had problems with this car and thereafter I couldn't get it to run at all. Makes a good project for someone who has a lot of knowledge on Z's...." but you will add "or is willing to listen to the people at the recognized source of Z information on the net that kept telling me NOT to muck everything else up while fixing ONE problem."

Sorry to be blunt, but I've seen this song and dance played out to the same disastrous end too many times to want to see it again. Check the vacuum advance, then check the timing, then check...... notice nobody has said go muck with the richness of the mixture to try to get it to run. The car is currently in a RUNNING state, although out of proper adjustment. i.e. the engine starts, and continues to run, although it can't hold a smooth idle nor accelerate properly. That says it IS getting AIR and FUEL and SPARK (the engine IS running). You've already eliminated compression, so the next thing is TIMING i.e. FINE adjustment. You can eliminate the fouled plugs later AFTER it's running smoothly.

2¢

Enrique

[Daniel]

Those are not choke slides. They are nossiles. They work with the choke. Look into a carb with the carb piston up. You'll see the status of the flap.

[messenger]

double post.

[messenger]

EScanlon, so your saying that there is another vaccum advance plate at the bottom of the dizzy, Under all of the counterweights? I have checked the one that the points bolt to, it has 3 ball bearings and I would assume it is the vaccum advance plate. Considering it is hooked into the vaccum advance diaphram. Maybe I am incorrect in my assumption but it seems correct.

I should have mentioned earlier I did rev it up pretty hard. I brought it up to 3500-4500k very fasy on quite a few occasions. It revs nice and smooth.

Oh yea on more thing, don't think this car is gonna end up on ebay for 500. bucks. I'll drop a good ole' 4g63 in there long before that happens something I am a little more familiar with

[beandip]

There is the vacum advance, and then there is also the centrifitical , wrong spelling, advance . This secound advance is the one that takes over when the rpm come up. as the counter weights spin they overcome the springs and advance the timing. The vacume advance is for when the engine comes under load at the lower rpm , it advances the timing to generate more power. Did you clean the crud and dried up grease out of inbetween the plates and free them up and regrease the ball bearings. I just think that escanlon was trying to get your attention about scattering your attention in several directions. This is how I bought my car , the PO had decided to tune it because he dident think it was running right. He put champion plugs in , first mistake, then when he attached the wires he swaped two . I ran like crap so insted of checking the wires he started messing with the carbs . Then It really ran like sh$$ . So then he adjusted the timing and on and on and on. So he decided to sell it . He did have two and was building the other one. When I brought it home I found one carb was lean one was rich the air ballance was way off , the timming was 10 deg RETARTED. I paid $500. I tuned it new NGK plugs and drove the car for a year before starting a serious redo. Ran like a champ 23 mpg and all. If you want a piece of advice , listen to the people trying to help. reread the threads pay attention to the ' take it one step at a time '. you will get posts like. Check the bumper bolts because the engine is running bad. Will almost that bad. They seem to get on the thread form time to time .Gary

[calliebrat]

My name is Stacey. I have a '74 260 Coupe. I'm going to tell you to try something that might sound crazy but I've seen it with my own eyes and she ran way better. Take off the cover to the air filter, get the water hose with a spray nozzle on it- rev the engine to about 3500 rpms and spray a fine mist into the intake for about 10 secs. The car smoked brown smoke- did it again and it smoked white and once again it didn't smoke at all. My car also has the round tops and believe me he knew what he was doing. It cleaned my heads and pistons at the same time. I couldn't believe it. I love my carb. guy. Told you it sounded crazy. Get a hold of me @ cornish_stacey@yahoo.com.

[beandip]

Been there done that , you need to be careful injecting water into the air stream. How ever it can knock some of the carbon buildup off. The situation we have been covering does not involve pinging or predetination , which the water treatment is ment to solve. Gary :classic:

[my_mad_z]

Could it be possible that you're not getting adequate spark to ignite the fuel? I had a similar problem with my Z, would back fire and carry on when I ran the motor (backfire through the carbs, miss, and rev poorly)..... I disconnected the battery while the car was running and the revs picked up and it ran smooth. Turns out my altenator was stuffed and there wasn't enough voltage going to the coil. I'm not sure if you have points or electronic dizzy, but a low voltage supply can affect the strength of the spark, especially with an electronic dizzy. I haven't had time to read through all the posts, but it might pay to check the altenator brushes to see if they are worn.

Marc.

[sblake01]

Good call, Marc. I don't know how that affects the carbureated cars but having been through that with my 810 I know it sure affects the f.i. cars.