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Dies Under Load


NCdatsunZ

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I have a 1972 240z with round tops. I rebuilt the carbs with the Ztherapy kit.

I got the car warmed up and tuned them as best I could but when I went to drive the car, it struggled to move along. The car revs up fine while in neutral. I tried messing with the timing and it did nothing to help.

I checked the vacuum advance in the distributor and it appeared to be functioning properly. The spark plugs are new. I pulled the fuel lines that go from the fuel rail to each carburetor and cranked it for 20 seconds or so and they both flowed well and the gas was clean. The float levels have been set properly. I took the return fuel line of and blew air through it and i could hear it bubble towards the back of the car, I'm not sure how easy it should be to blow air through the line but it seemed ok.

Any help would be much appreciated. This car is driving me crazy :ogre:

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Next time, warm it up and try giving it some choke as you put the engine under a load. That will tell you if the mixture is too lean. Some additional info is needed; Was the engine warmed up? How many turns down are your nozzle screws? Color of the plugs? What was your reason for the carb kits? Did it run poorly before? Did you work on anything else when the carbs were off? Given the info at hand, my first choice is it's too lean. Check; fuel filters, fuel pressure & volume, float level. Mark in Portland

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please clarify ' struggles to move along'.

Load and no load is big difference on how it runs.

Get a timing light-they are cheap and this eliminates things

Well I tuned the carburetors to the best of my ability, rolled it down the driveway (slight incline) and attempted to drive back up the driveway and had to rev it up and dump the clutch constantly to get it back up.

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Before you did a rebuild on the carbs, did it drive then ?

The car sat for a number of years before the carburetor rebuild. I had the gas tank boiled out and sealed professionally and double checked to make sure that none of the lines were clogged (return line and vent lines). I blew out all the gas lines. New filters, coil, distributor cap, points, coil, spark plugs, wires, etc.

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Did some tinkering today and found that no matter what I did I couldn't get the front carburetor to suck nearly as much air as the back carburetor. Just some more bit of info for you guys.

I uplugged the coil and the fuel line to each car and cranked it for 20 seconds or so again and found that the front carb did not have a steady flow of fuel whereas the back carb did.

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Since you still have points you can dead time it.

I went out and bought a timing light and set it. Also I pulled the plugs and they're a little dark. It took me about 4 tries to get the float levels right using the clear fuel tube method so I don't know how it could be the float levels.

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The car sat for a number of years before the carburetor rebuild. I had the gas tank boiled out and sealed professionally and double checked to make sure that none of the lines were clogged (return line and vent lines). I blew out all the gas lines. New filters, coil, distributor cap, points, coil, spark plugs, wires, etc.

New fuel pump?

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Hopefully you watched the DVD that Ztherapy offers. There are two different drop tests for the pistons. Both are important. I would pull both tops and pistons and try swapping pistons, On mine, I found they had a much closer fall rate than before. A little buffing on the slow one and they were identical. Screw the nozzles up til snug, Install the pistons springs and tops. When doing the drop test, listen, they should sound exactly the same. Lower the nozzles 2 1/2 turns,fill the carbs with oil and give it another try. Mark in Portland

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