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Discussion Starter · #1 ·
I have a 1972 240Z that I would like to restore. It has been sitting for few years and I would like to get it running. The engine is a stock rebuilt L28 (N47 head, F54 block) with an auto transmission (I plan to convert to a 81-83 5-speed and 3.90 diff). The carbs are 40 SK Racing (Weber copy) with jets that are inter-changable with Webers. These are the current specs on the carbs:
Emulsion Tubes: F11
Main Jets: 130
Air Corrector Jets: 120 - 200 ????
Pump Jets: 40
Idle Jets: 50F9 ??? Can't read the # very well
Pump Ex Valve: closed
Main Venturi: 32
Aux Venturi: 4.5
Needle Valves: ??? Can't find a #

I don't believe the carbs are setup right, so what jets do you recommend I should start with. I hope I gave you enough info to make a decent recommendation. If not I can provide addittional info. Well I think this is long enough.
Thanks
 

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<b>ZR8ED here! Helps on the way.</b>

You didn't mention anything about cams or header/exhaust so I'll assume your engine is completely stock.
Your emulsion tubes sound ok. I would not change them right away. They control WHEN the main circut starts to take effect. The Z calls for F11 emulsion tubes anyway. F16 are probably the best (at least for high output Z's)
Your main jets are an excellent start point for your engine. Leave them for now.
Your air correctors sound like they are not all the same. WHENEVER YOU CHANGE ANY JETS MAKE SURE YOU GET 6 (ONE FOR EACH CYLINDER) You need to start with air correctors that are 180's (all six) They control the amount of fuel your engine gets at high rpm.(approx 4500+rpm) 175's will give you more fuel and 185's will give you less fuel.
Your pump jet is too small try 50's. They give you an extra shot of fuel when you FLOOR it. If the car bogs when you floor it your pump jets are too small.
Your idle jets are right on though keep an eye on your sparkplugs after extended idling they may start to foul. If so try 50F8's. They are a bit leaner.
The "pump ex valve"(closed) I don't know what your talking about there. ????
Your main venturies (32mm) will do for now. the car will be plenty driveable and quick for now. I personally recommmend 34mm which will give you better hp in the 4000-redline area. If you like to push the car hard this is the way to go.
Your Aux venturi is just fine leave it alone.
Needle valves. I assume that you are talking about the needle valves that control the fuel flow to the float bowls. I think that I use 223's. as long as they are bigger than 170's you will be fine. The numbers are hard to read because the float is usually in the way. I would leave them alone for now. (what were the carbs off of before?) They are probably Ok. If they are large, they will just do a REALLY good job of keeping the float bowls full. If they are to small they will not be able to keep up for extended high rpm runs.
Lastly invest in some kind of unisyn for balancing the airflow to each carb. Also, if possible find a manual for the SK's or even webers for that matter. It can really help with trouble shooting.
Is that too much info?
Let me know if you have any other questions/info about your progress.
ZR8ED. Good luck!
 

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Discussion Starter · #3 ·
RE: ZR8ED here! Helps on the way.

Thanks so much for replying!!! You truly are the Weber guru. The engine has a stock cam, however I do have headers and 2 1/2" exhaust. I don't know if this will change the settings that you recommended. The carbs were bought new from Motorsport years ago when they were still available. The mechanic that installed them claimed to be a weber expert, however I seriously doubt it since he installed the different size jets into the carbs. I do have a manual for the SK and Weber, they were a great help in identifing the jet sizes.
Again thanks for your help and I'll keep you posted on my progress.
 

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<b>Don't worry...........:)</b>

Your welcome!
Don't worry about the headers and the 2.5" exhaust. It will not affect my jet recommendations.
ZR8ED.
 
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