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1971 240z carb question

2846 Views 10 Replies 7 Participants Last post by  vigman, 
B
Hello there, i have a stock 1971 datsun 240z with the side draft carbs. I have added the k&n air filter kit from motorsports and it had jacked up the air/fuel mixture and it is running to lean now. I have talke to a local mech and he wants to drill out the jets so more fuel is added in the mixture. Is this the correct fix for this problem? I have order the z therapy video so i can understand a carb set up but the wife will not get it untill christmas...so thought i would ask you guys. Other than drilling out the carbs, is there another adjustment i can do to correct the air/fuel radio. Also the symypons of the car is hesentation at first gear, but push through it and it works its self out, some backfiring and popping at the air filters. Just thought i would throw that in there. Some help would be great to verfify what i am being told before i spend the money, or maybe so it my self....willl wait for the video before that happens. Thanks for your help
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T
Have you first tried tuning the carbs to see if you can adjust the lean mixture?

If that doesn't work, what about changing needles?

I really don't see why you need to go drilling anything in the carb.
Even when i put in a rougher cam, all that was needed was a new needle to get a better fuel/air ratio and a tune up.
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B
Your mechanic is nutz! There is a fuel richining screw (large nut) on the bottom of each carb. Start by lowering (unscrewing) it about 1/4 turn on each carb. Run a while, if pop is still there lower a bit more. Read plugs. Don't be moving any needles yet. Best to get the video for hands on learnng. No need for new needles or drilling. These carbs are so simple once you learn how and why they work.

Bonzi Lon
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black gold man
How much oil did you put on the k$n filter.To much will muck up your carb and restrict air flow.
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T
Yeah don't let that mechanic near your car again.
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vigman
Drilling Jets is fine for a holley 650 ( when your to cheap to buy the correct jets ) NOT on a Z!!!

K&N = more air ( and more junk thru the air fliter.. into the engine ).

IF your popping.. your lean.. read your plugs!

Mike
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W
How was it decided that is too lean? Don't let that so called mechanic within three miles of your car.
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B
i was told it was lean from the poping and from the hesentation (spelling) in first gear. I will be reading the plug in a few minutes and will repost.


Update i have pulled all the plugs and they are light brown in color, confirming the "lean" status that i suspected
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B
Well i have followed some dirrections (first time for everything) and adgusted the screws on the bottom to the point where the hesentation is gone from 1st gear and it runs like a top. I was also able to synronize the carbs with the special tool that caem with the car, to the point where the red float is in the same position when put on both carbs. I will wait till tomorrow and do a cold start and see how it goes before making any other adjustments. Thank you for all your help guys. Merry christmas
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B
That video will be of more help than you can imagine. The sync tool is a must to tune for beginers, glad you have one. The adjustments so far should get you going until you get the video, if you can keep from tinkering untill then.

Bonzi Lon
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vigman
And no drilling involved!

Happy Holidays~
Mike
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