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Old 01-03-2003, 09:21 AM
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Post Adjusting a speed demon carb

I have a 79 pontiac trans am with a 403 olds that I have rebuilt. It should produce around 350 hp. I installed a 750 speed demon carb, but I can not seem to get it to run quite right. I believe I have the air fuel ratio set correctly. I used a vacuum gauge to set it. I have played considerably with the jetting, but I am still having problems. When I am driving along if first gear at around 3000 rpms I am in the begining part of the real power curve of my engine. If i punch it, the car will take off like a bat out of hell for just a second or so, then it will loose considerable power for another second or so, then it will take back off at about three quarter power of what the initial takeoff was. Any ideas would be greatly appreciated. thanks for the help guys

[ January 03, 2003: Message edited by: Bradless ]</p>

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Old 01-03-2003, 12:01 PM
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It could be 1 of 2 things. First is a vacumm leak or your running out of fuel. Since it dont backfire when you hit it, you mite need a longer shot on the acceleator pump so your engine can catch up. Also check your float height.
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Old 01-03-2003, 03:29 PM
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Thanks for the info. I adjusted the floats up higher and found it to help. While I was doing that a neighbor of mine who I did not know stopped by and helped me. We also found my rear butterflies were open a little so we adjusted them and the idle mixture. The demon carb I have does not have an adjustment to the linkage for the accelerator pump so we also put in slightly larger jets which also helped. Runs like a champ now. Thanks for the help.
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