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HybridZ

S.U. vacuum differential??


Guest Anonymous

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Guest Anonymous

Hello, im helping a buddy with his upcoming 280 powered 240 which has a set of SU' s. I rebuilt them for him,(because i rebuilt mine when i was using the 6) i had no problem running them on my 2800, but i cant seem to get these! the back carb seems to be doing all the work. lots of vacuum at the inlet of the back carb but the front one doesnt have any till your hand is right on the inlet then it will suck hard enough to pull your hand and make the idle climb, but not even close to as much as the back!!! fuel pressure maybe?? spark to all 6 but its like the back three are doing all the work. carbs have been cleaned very thorougly.. it has points and condenser style ignition. any ideas??? Thanks, DAN

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Guest James 72 240Z

A couple of things to check (my apologies if these sound too rudimentary!):

 

Is the vacuum advance port on the front carb being utilized? If not, is it plugged (could be a vacuum leak if not)?

 

Do you have the same weight of oil in both dampers? Have you done a piston drop test i.e. if you push both pistons up to the top and let them drop do they clunk on the bottom at the same time? If the back piston works better than the front than it will rise easier and draw more fuel into the motor vs. the front carb.

 

Are the float boal vents plugged or unplugged? If the front vent is plugged then gas will not be able to flow into the float bowl properly.

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