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Old 09-05-2009, 10:07 PM
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454 problems

I just dropped in a fresh rebuilt 454 in my truck and fired it up on the second try, after a minute or so it bogged down and turned off ? the carb 750 holley was rebuilt and it appears the floats were never adjusted and flooding was the problem ? we pulled out plugs let it sit and it fired again for a minute or so then bogged down again ? after turning the top float adjusment nut 2 turns clock wise and changing plugs it will not turn over at all ? and i also forgot to add that it would backfire once before turning over ( carb ) please give me some direction

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Old 09-06-2009, 01:03 AM
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Quote:
Originally Posted by truckboy61
I just dropped in a fresh rebuilt 454 in my truck and fired it up on the second try, after a minute or so it bogged down and turned off ? the carb 750 holley was rebuilt and it appears the floats were never adjusted and flooding was the problem ? we pulled out plugs let it sit and it fired again for a minute or so then bogged down again ? after turning the top float adjusment nut 2 turns clock wise and changing plugs it will not turn over at all ? and i also forgot to add that it would backfire once before turning over ( carb ) please give me some direction
First off, lets get the terminology nailed down. "Turning over" means the starter is turning the crank. Firing means the motor turns over, fires and runs. Is it turning over and not firing or is it not turning over?
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Old 09-06-2009, 02:55 AM
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Correct it is turning over but is not firing.
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Old 09-06-2009, 03:07 AM
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OK, I was concerned there for a minute that you had hydrauliced a cylinder.

First things first. Use shop air to blow out all the spark plugs. I have sometimes been able to clean the fuel out of them with blasts of carburetor cleaner from a rattle can, but if you have shop air, blow them out thoroughly with a blow gun tip. Then shoot carb cleaner in there and blow that out with your blow gun tip. Watch your eyes and do this in a very well ventilated area. Might even hold your breath as you do each plug. You don't want to inhale any of this stuff. Even going through all these monkey motions, sometimes I have had to go buy new plugs.

Next is fuel pressure. You want no more than 5 psi at the carb inlet. More than that WILL NOT make more hp. It will blow fuel past the needle and seat and flood the motor again. You will need a good-quality 0-15 lb gauge to test with. Is your pump mechanical, driven off the cam, or an electric pump?
http://www.summitracing.com/parts/HL...0/?image=large
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Old 09-06-2009, 10:39 AM
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My pump is mechanical and I've placed in new plugs. how many turns shoul i have adjusted the float level
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Old 09-06-2009, 05:02 PM
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Are the floats externally adjustable? Do you have a sight glass or plug you can remove to check fuel level? Post the carburetor part number. It's stamped on the carb.
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Old 09-06-2009, 05:29 PM
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The # is 9188 carb 780 and it does have a top screw and nut underneath to adjust float and a screw on size to allow gas out. I just pulled spark plug and they are not wet at all ? perhaps I turned float adjustments to much or there's no spark ?

Last edited by truckboy61; 09-06-2009 at 05:35 PM. Reason: left out
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