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> Dual Carburetor Tuning, Need to learn
Flyover914
post Jul 2 2019, 07:11 PM
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I've nearly completed a home hobby restoration of a '72 914. It was not a matching numbers car and the engine was originally a 1.8 so came from a '73 or '74 car? But still came from a 914 so I've been working with what I have. The fuel injection system was long gone when I purchased the car so the restoration/rebuild was done using a dual carburetor. Unfortunately I live in an area where no one is willing to attempt to tune a carbureted car. Seems it is a dying art.

I'm at a point where the car starts and runs fairly well once its warmed up. And it is driveable..... but its just not right. I've gotten it this far with very limited carburetor knowledge and a few YouTube videos but all I'm really doing is turning adjustment screws for idle mixture and idle speed without really understanding.

I'm asking for a reading list so I can teach myself how to tune my dual carb setup. Does anyone have a "must read" list? My current setup is a pair of EMPI HPMX. They look a lot like Webers so I think anything Weber related will at least get me in the ballpark. Need a good starting point to build from. What have you guys got?

Thanks!
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Dr. 914
post Jul 3 2019, 07:26 AM
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you must start with a good valve adjust even compression dwell at 50 degrees and timing at 27 BTDC and the carbs are tightly sealed to the intake and the intake to the head

then make sure that the air correction are out two turns, the mixture are out two turns the idle are in two turns once they hit the stop and the accelerator linkage is disconnected. THEN with a air flow sync tool, check the air flow on the four barrels and adjust the air screws to the average reading for all four. Once the air flow is balance lock down the nuts on the air adjustment screws. Then connect a tachometer to the coil and while watching the dial, turn the mixture screws in one at a time until the idle starts to drop and then back out just enough for the idle to increase.

After that if the idle is 950 you are all set if not turn in the idle screws to achieve the 950 RPM keeping in mind the carb air flow balance

the
QUOTE (Flyover914 @ Jul 2 2019, 07:11 PM) *
I've nearly completed a home hobby restoration of a '72 914. It was not a matching numbers car and the engine was originally a 1.8 so came from a '73 or '74 car? But still came from a 914 so I've been working with what I have. The fuel injection system was long gone when I purchased the car so the restoration/rebuild was done using a dual carburetor. Unfortunately I live in an area where no one is willing to attempt to tune a carbureted car. Seems it is a dying art.

I'm at a point where the car starts and runs fairly well once its warmed up. And it is driveable..... but its just not right. I've gotten it this far with very limited carburetor knowledge and a few YouTube videos but all I'm really doing is turning adjustment screws for idle mixture and idle speed without really understanding.

I'm asking for a reading list so I can teach myself how to tune my dual carb setup. Does anyone have a "must read" list? My current setup is a pair of EMPI HPMX. They look a lot like Webers so I think anything Weber related will at least get me in the ballpark. Need a good starting point to build from. What have you guys got?

Thanks!

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Flyover914
post Jul 8 2019, 07:29 PM
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Okay. Very helpful! I wasn't starting with the idle mixture screws far enough out and kept turning the screws in for a lean mixture. Lots of popping and poor pedal response. Starting 2 full turns out it was obvious I had been starving the engine. Much improvement but still one thing bugging me. Three of the four stacks have matching air flow. One is problematic. It always measures 1.5 to 2 below the other three. All the air correction screws are turned in and snug with locking nuts. I could not tell there was any difference to that one stack when I made slight adjustments to the air correction screw. What should I look at next?
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Dr. 914
post Jul 9 2019, 08:30 AM
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compression valve adjust and intake leaks. Those are the causes of low air flow in one barrel.

QUOTE (Flyover914 @ Jul 8 2019, 07:29 PM) *
Okay. Very helpful! I wasn't starting with the idle mixture screws far enough out and kept turning the screws in for a lean mixture. Lots of popping and poor pedal response. Starting 2 full turns out it was obvious I had been starving the engine. Much improvement but still one thing bugging me. Three of the four stacks have matching air flow. One is problematic. It always measures 1.5 to 2 below the other three. All the air correction screws are turned in and snug with locking nuts. I could not tell there was any difference to that one stack when I made slight adjustments to the air correction screw. What should I look at next?

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Flyover914
post Jul 10 2019, 07:36 PM
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Great. Thank you so much! Haven't been able to find that bit of information anywhere. Now I know what to dig into.
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