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The S-10 and Blazer was arguably the most versatile and accessorizable mid-size truck and SUV on the market.
Platform: S/T-series & GMT 330

tbi to carb 4.3

Old April 4th, 2019, 2:54 AM
  #21  
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Originally Posted by charlie2sods View Post
i got 18-20 so i guess its ok, i got a new 2100 motorcraft carb on this 4.3 and it has a little hesitation when you start to open it up, i havent got that figured out , but i got it running, just need to get a hot wire from the switch for the electric fuel pump, and then i will have my old school truck no puter, no sensors.
Yeah, those were the days. Lots of pickups didn't have a fan shroud so changing out the radiator, water pump or the engine mounted fuel pump was a piece of cake. Of course, the gas tank was behind the seat ( no extra cabs back then) so not as much space to put anything in the cab, Run the wheels off that pickup!
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Old April 4th, 2019, 3:29 AM
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timing and where do you have the vacuum advance hooked up to?
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Old April 4th, 2019, 7:11 AM
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i have the timing at 8 degrees btc right now, it fires as soon as you hit the key, the vacuum advance is hooked to the port in front of the choke in the base of the carb, small line maybe 3/16 is my guess. Im wondering if the timing could be off causing the hesitation, what do you think
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Old April 4th, 2019, 1:24 PM
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I run my 350s around 15-16 and run manifold vacuum. Meaning at idle I'm around 32 degrees advance and the throttle response is outstanding.
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Old April 7th, 2019, 8:58 AM
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guys i need a little advice, i got this conversion done from throttle body fi to carb motorcraft 2100, when the vacuum line is hooked up from the carb to the vacuum advance on the distributor, it is causing a low idle issue with the carb and appears to be missing when starting to raise the rpms, when i unplug the line from the carb it runs smooth. I did check the timing with it hooked up and it is advancing, Im not showing any vacuum with the guage hooked to the carb at idle at 7-800 when when i accelerate it shoots down to about 25, the other vacuum line that hooks to the intake shows about 18-20 vacuum, what am i missing here, thanks

Last edited by charlie2sods; April 7th, 2019 at 10:51 AM.
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Old April 7th, 2019, 11:57 AM
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Perhaps the vacuum advance diaphram has a hole in it, or the line?
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Old April 7th, 2019, 12:48 PM
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this is a new hei distributor with coil on top and new line
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Old April 7th, 2019, 6:12 PM
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the one with no vacuum at idle is ported the other with vacuum when the engine is running is manifold. i dont understand how unplugging the VA is causing a change in idle when theres no vacuum present. but you should have the VA plugged into the manifold vacuum, you'll get better performance that way. the reason GM hooked it to ported is for better idle emissions.
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Old April 7th, 2019, 7:20 PM
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Originally Posted by kevinkpk View Post
Perhaps the vacuum advance diaphram has a hole in it, or the line?
Not unusual at all for the vacuum advance to have problems. I have changed out a bunch them in my lifetime. At least they are cheap and easy to replace. Used to hate changing points, thankfully electronic ignition came around about 1970-1972. My fathers old 69 C-60 366 mill ate points up every month. Soon as a conversion unit to E-I was available for it, I installed it. Boosted power and gas mileage both, win-win and no more points and condensers to change!!
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Old April 7th, 2019, 7:37 PM
  #30  
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Originally Posted by charlie2sods View Post
i have the timing at 8 degrees btc right now, it fires as soon as you hit the key, the vacuum advance is hooked to the port in front of the choke in the base of the carb, small line maybe 3/16 is my guess. Im wondering if the timing could be off causing the hesitation, what do you think
I know you said its a new carb, so your power valve diaphragm should be good to go. You might need to do some re-jetting for your particular motor. Have you tried hooking up your vacuum advance hose to a different intake outlet yet? That might be a possible cause as well. I am assuming that you set the idle screws with a vacuum gauge?
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