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  #1  
Old 11-06-2017, 10:14 AM
datsunnyit datsunnyit is offline
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240z rpm & hitachi carburetors (su type)

Unstable RPM.
why ?

https://www.youtube.com/watch?v=AUw8...ature=youtu.be

https://www.youtube.com/watch?v=EPBp...ature=youtu.be
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  #2  
Old 11-06-2017, 10:32 AM
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jonbills jonbills is offline
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An air leak somewhere maybe.
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Old 11-06-2017, 10:57 PM
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SacCyclone SacCyclone is offline
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Check to see that both of the main jets on the SU's are pushed up completely with the choke off.

Put a timing light on that engine and make sure your timing is not jumping around too.
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1971 240Z Street/Track
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Old 13-06-2017, 10:05 AM
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TimW TimW is offline
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Carb Throttle Shaft wear maybe.
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Old 13-06-2017, 01:59 PM
Nigel Brook Nigel Brook is offline
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Certainly carb related. How old are your carbs?
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Old 16-06-2017, 09:07 PM
datsunnyit datsunnyit is offline
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new carbs some various thousand km but is new from USA remanufactured company.
always have this problem
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Old 16-06-2017, 10:36 PM
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What happens if you unplug the vacuum advance from the distributor?
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Old 17-06-2017, 10:23 AM
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If they were older carbs, I would have said to balance them using an air flow meter and then check the float level settings but not normally on rebuilt carbs.

With new or remanufactured/refurbished ones, I would still suggest balancing and it may even be worth checking the floats and float valves as they can sometimes stick or be set incorrectly. You might even have a bit of dirt or metal in the bottom of the float chamber left over from the rebuild that could be blocking things.

You might also want to contact the company that rebuilt them and ask if they set them up before they leave the workshop.
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