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258 4barrel |
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5spdwagon 
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Joined: Jun/29/2012 Location: Guy ton ga Status: Offline Points: 522 |
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 Topic: 258 4barrelPosted: May/27/2018 at 8:31am |
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Has anyone had any luck using a holley 390 carb on a stock 258? I have one on my car but I have a dead spot in the carb off idle. I can not seem to get rid of the dead spot. I can adjust it and get it to move in the rpm rage but can’t get rid of it.
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Real hot rods have 3 pedals
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Greyhounds_AMX
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Joined: Nov/14/2009 Location: Kansas City Status: Offline Points: 1268 |
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Posted: May/28/2018 at 8:09pm |
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I'd expect that you need a larger accelerator pump squirter.
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1968 AMX 390 w/T5
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5spdwagon
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Posted: May/30/2018 at 2:35am |
I may try that. That’s the only thing that I can think of that is the issue. It ran fine on a 231 Buick a few years ago so I figured both the Buick and my 258 were about the same power so I thought it may work. So far nothing I have tried has done any good. |
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Real hot rods have 3 pedals
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Trader
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Posted: May/30/2018 at 6:03am |
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An I6 has longer intake runners and a more pronounced vacuum signal then a V8 or V6.
It's likely getting too much air/fuel and bogging until it reaches an RPM that vacuum signal to the carburetor steadies more. Try jetting the carburetor down and see how it performs. |
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5spdwagon
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Posted: May/30/2018 at 1:08pm |
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I have tried up and down 2 sizes on jets did not make it any better the larger ones made it worse
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Real hot rods have 3 pedals
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tyrodtom
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Posted: May/30/2018 at 3:20pm |
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Which intake do you have the 390 mounted on ?
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66 American SW, 66 American 2dr, 82 J10, 70 Hornet, Pound, Va.
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Greyhounds_AMX
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Posted: May/30/2018 at 3:22pm |
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Off idle would be pump shot thougb, main jets are later. Every 258 I've built with a 4 bbl Holley needed more pump shot. Most needed the high volume accelerator pump conversion.
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1968 AMX 390 w/T5
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5spdwagon
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Posted: May/31/2018 at 2:03am |
Clifford intake |
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Real hot rods have 3 pedals
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Greyhounds_AMX
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Posted: May/31/2018 at 12:47pm |
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I would start with a 31 squirter and a blue pump cam on position 2. Also run as much initial timing as you can get away with as that will help.
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1968 AMX 390 w/T5
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5spdwagon
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Posted: Jun/01/2018 at 12:22pm |
Timing is as high as the motor will take it and still crank good. |
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Greyhounds_AMX wrote: