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Stumped in New Mexico


robox

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Also, all timing right now is being done by just cranking the engine over with the starter (which I am doing with a rigged push-button) as I obviously cannot get the engine to run right now. I don't know if that makes much of a difference.

In the past I have had to use liberal amounts of starting fluid to get this engine going, and as I pointed out in my opening post I am currently out of it. I'm gonna buy some more and see if I can get it to run on that. If it does... Maybe that would mean I'm having a fueling issue???

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Thank you, madkaw and everyone else, for reading and re-reading my post and giving it some thought.

I agree that it makes a lot of sense to conclude that the problem must be related to when I screwed with the carbs. The problems with this theory are that A) I am actually reasonably familiar with the carbs, and B) I did not do much to them.

When I first bought the car in SoCal it was not running too well, so I gave myself a crash course on the carbs on the internet and then rebuilt them with good results. The car ran better. What I did last weekend was simply remove the domed tops, piston springs, and pistons, clean them, and replace them. Also I checked the number of turns on the butterfly adjuster (idle) screws and then returned them to their original positions. That's all. AFTER it became clear the car didn't want to start, I then did some other things such as fine-tuned one float level to give a fuel level of 23 mm from bowl top and also replaced the oil in the dashpots with 10W motorcycle fork oil. I'm familiar with the drop test and the pistons are dropping and clunking well... if anything better than before.

Thanks,

Christian

Edited by robox
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I would go back over everything you wired with the Pertonix and make sure nothing is loose . Pics of your wiring?

It will hard to get past the issue of your timing being Way Off. For me, I would have to have that right first. 35 degrees is saying something is wrong and needs to be addressed.

Checked for vacuum leaks?

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Is your car an automatic by any chance?

Are you checking the timing with the vacuum advance disconnected? I just checked my AT Series I and it measured 30.2 degrees BTDC at 840 RPM with the vacuum line connected and 10 degrees BTDC at 1000 RPM with the vacuum disconnected.

I know that Chilton says to set the timing with the vacuum connected for these models. But now I'm confused.

The 1970 factory service manual does not give any specs for A/T cars since they were introduced mid year. They say to set the timing using a strobe light and to set timing to 5 degrees at 750 RPM for SU carbs with emission control and 17 degrees at 750 RPM for SU carbs without emission control. But they give no instructions about whether the vacuum line should be dis-connected.

The 1972 manual gives no additional instructions regarding the vacuum line but gives emission control timings of 5 degrees at 750 RPM for MT and 0 degrees at 780 RPM in neutral for AT. Chilton agrees for the 1972 model year.

Haines says the static timing should be 10 degrees at 550 RPM MT (16 degrees at 650 RPM AT) with centrifugal advance of 0 degrees at 550RPM and maxing at 9 degrees at 1200 RPM. Vacuum advance starts 3.94" Hg and maxing at 7.5 degrees at 13.0" Hg. for A D609-56A Distributor.

Just what is the proper procedure for checking timing for our cars?

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I can't really speak to the proper method of timing these cars, as I am something of a novice (which is probably quite obvious by now!!) But anyway, I also would like to know the answer. It does seem to me that the vacuum advance should probably be disconnected... but hopefully someone else more experienced on the topic will chime in.

Just to re-visit a question that seems to have gotten lost... Is it even possible to have the distributor shaft installed one gear tooth off?

I am gonna go work on the Datsun for a few minutes now, before I get to what I am really supposed to be doing today. I will see if starting fluid reveals any new information.

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I think that the question of the distributor being off one tooth has been ignored because the engine ran before. It's kind of irrelevant, and a red herring, which will distract you from what's really wrong. The oil pump drive can be off one tooth, which then puts the distributor off because the distributor is driven by the oil pump. If you never too the oil pump out and the engine ran before, then the oil pump should not be the source of your problem.

Transistor ignition systems can fail partially, to where they'll give spark, but not a strong spark. You may be getting spark outside the cylinder but not inside under pressure and fuel/air mixture. The suggestions about re-installing the points are good ones. Go back to what you know worked, take out the unknowns.

In other words, try to get the engine back to exactly like it was when it ran, then start the improvement cycle over again.

Edited by Zed Head
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Thanks Zed Head. I've been thinking the same thing.

The situation did NOT improve with starting fluid. Still nothing more than occasional burping on cylinder 6. header pipe 6 is the only one that got warm.

To be honest I am getting a bit discouraged. I will try reinstalling the points. If that does not work I will tow the car (which drove itself in a week ago) out and put it in storage, I guess.

Edited by robox
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Zed's Right. Pertronics makes a good product, I've installed them on many cars. I've also had MANY pick up failures. To the point where when I do a conversion, I always recommend keeping a spare pick up in the glove box. Just try the points again, remove the variable. With either set up, make sure you are properly at TDC #1 for your starting point. Your timing figures do sound off.

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OK, so.....

I re-installed the old points and there was a marked improvement. Suddenly it sounded like it was running on 3-4 cylinders instead of 1-2. I noticed, however, that opening the throttle produced no increase in engine speed, whatsoever, even at WOT.

Then I put in new plugs, which did not seem to make much of a difference.

Then I started playing with the timing, and the car came back to life, albeit only when the timing was put back up around 30º, where it used to be when all this started. Here is how it behaves with regard to timing:

0º: engine will not start, no matter what.

5º - 10º: engine will start and idle poorly, opening the throttle produces no increase in engine speed.

20º - 25º: engine idles pretty well, but throttle response is slightly sluggish.

30º: engine idles well, throttle response is nice and crisp.

What does all this mean? I haven't got a clue. I know some advance can be called for due to high elevation (I am at 7000 ft) but I do not know how much is appropriate.

For now, I am just happy it's running again. Seems like the Pertronix pickup was crap.

One other thing to note... on top of each float bowl is a nipple fitting, and there are hoses which attach there that join up and appear to go back to the tank. I am guessing they are overflow lines. Anyway, if I attach those hoses to the nipples, the engine appears to fuel-starve and dies pretty quickly. I need to leave those nipples open for the car to run.

Also, the exhaust is really unpleasant... makes my eyes tear immediately. Seems rich... although the "briefly lift the carb pistons and observe idle speed" test indicates that the mixture is close to right.

C

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Those are float bowl vents and should be left open to atmospheric air.

I thought you had already gone back to your previous timing before this.

As stated earlier, you need to get this issue resolved(timing). If you are going to own a Z , this is right to passage to work on these engines. There are hundreds of threads on this so get searching :)

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